WO2013145109A1 - 非水電解質二次電池用電極、非水電解質二次電池と電池パック - Google Patents
非水電解質二次電池用電極、非水電解質二次電池と電池パック Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/387—Tin or alloys based on tin
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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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
Definitions
- Embodiments of the present invention relate to a nonaqueous electrolyte secondary battery electrode, a nonaqueous electrolyte secondary battery, and a battery pack.
- Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries have a high energy density, so they range from small portable devices such as personal computers and smartphones to large power supplies such as electric vehicles and power leveling power supplies. Although it is used in the field, since it is more expensive than a water-based electrolyte secondary battery such as a nickel-hydrogen secondary battery, a long life is required to suppress replacement frequency.
- the reaction mechanism that deteriorates while the nonaqueous electrolyte secondary battery is repeatedly charged and discharged is not necessarily clear, but for example, the following reaction mechanism has been proposed.
- the non-aqueous electrolyte secondary battery has a higher voltage than the nickel-hydrogen secondary battery because the potential of the negative electrode of the non-aqueous electrolyte secondary battery is low and the potential of the positive electrode is high.
- a non-aqueous electrolyte electrode is prepared by kneading an active material together with a binder and applying it to a current collector.
- the active material is highly reactive in the charged state, and the binder reacts with the active material. By doing so, the binding strength between the active material and the conductive material is weakened, and the capacity may be reduced.
- the binder may be swollen by the organic solvent constituting the nonaqueous electrolyte, the binding force between the active material and the conductive material may be reduced, and the capacity may be reduced as the resistance is increased.
- Embodiment aims at providing the electrode for nonaqueous electrolyte secondary batteries excellent in the capacity maintenance rate, the nonaqueous electrolyte secondary battery, and the battery pack.
- An electrode for a nonaqueous electrolyte secondary battery is an electrode having an active material layer including an active material and a binder containing fluorine, and a current collector bound to the active material layer.
- the thermal decomposition start temperature of the binder is determined by the weight reduction process in the weight reduction process in the main weight reduction process when the binder is analyzed by thermogravimetric analysis. 5% decrease
- the thermal decomposition end temperature of the binder is 95% of the weight reduction in the weight reduction process in the main weight reduction process when the binder is analyzed with a thermogravimetric analyzer.
- the peak area is the ion chromatograph extracted at mass numbers 81, 100, 132, and 200. It is the peak area of the mass number that gives the maximum area.
- the negative electrode 100 includes a negative electrode active material 101, a layered negative electrode active material layer 103 including a binder 102 that binds the negative electrode active material 101, and a negative electrode. And a current collector 104 bound to the active material layer 103.
- the negative electrode active material layer 103 is formed on one side or both sides of the current collector 104.
- the reference numerals are omitted except when referring to the drawings.
- the negative electrode active material of the embodiment performs insertion / extraction of Li.
- the thing containing a metal element can be used among the negative electrode active materials used as a nonaqueous electrolyte secondary battery.
- the metal element include one or more metals selected from silicon, tin, antimony, aluminum, magnesium, bismuth, and titanium.
- the form of metal, alloy or oxide is preferable.
- the silicon in the metal state is preferably in the form of particles, fibers or flakes having a maximum diameter of 20 ⁇ m or less.
- the conduction distance of lithium ions becomes long, and the large current charge / discharge characteristics may be deteriorated.
- the particulate metallic silicon those having a particle diameter of 1 ⁇ m or less are preferable.
- Metallic silicon has a large volume change during charge and discharge, and if the particle size is large, it may be pulverized due to expansion and contraction during charge and discharge and fall off from the electrode, which may reduce the discharge capacity.
- silicon having a particle size of 20 nm or less is preferable because pulverization due to expansion and contraction during charging and discharging is suppressed.
- silicon having a particle size of 5 nm or less whose surface is coated is preferable in order to exhibit excellent cycle characteristics.
- the fibrous metal silicon is preferably one having a diameter of 1 ⁇ m or less and a length of 20 ⁇ m or less. If the diameter exceeds 1 ⁇ m, there is a possibility of pulverization due to volume expansion / contraction during charging / discharging, and if the length exceeds 20 ⁇ m, there is a risk of short circuit between the positive and negative electrodes through the separator.
- fibrous metal silicon having a diameter of 300 nm or less is preferable because pulverization due to volume expansion during charging and discharging can be suppressed.
- fibrous metal silicon having a helical higher-order structure is preferable because it can suppress changes in fiber length due to volume expansion / contraction during charge / discharge.
- the flaky metal silicon one having a side length of 10 ⁇ m or less and a thickness of 2 ⁇ m or less is preferable.
- the alloyed silicon include alloys with magnesium, iron, nickel, copper, and titanium.
- Mg 2 Si system as a magnesium alloy system
- FeSi 4 system as an iron system alloy
- SiNi system as a nickel alloy system
- SiCu system as a copper alloy system
- TiSi 3 system as a titanium alloy system, for example.
- Mg 2 Si alloy, FeSi 4 alloy, and SiNi alloy are preferable because of their large discharge capacity.
- tin When tin is contained as the metal element, a metal, alloy or ceramic form is preferred.
- the tin in the metal state preferably has a maximum diameter of 20 ⁇ m or less.
- alloyed tin include alloys with magnesium, antimony, iron, cobalt, nickel, copper, silver, cerium, and lanthanoids.
- alloys with cobalt, antimony, iron, and silver are preferable because of their large discharge capacity.
- ceramic tin include phosphides and oxides. Of these, phosphides are preferred because of their large discharge capacity.
- antimony is included as a metal element, a metal or alloy form is preferable.
- the alloy include alloys with indium, titanium, magnesium, cobalt, nickel, silver, aluminum, iron, and manganese.
- titanium When titanium is contained as the metal element, an oxide form is preferable.
- the titanium oxide include TiO 2 , spinel structure lithium titanate (Li 4 Ti 5 O 12 ), and ramsdellite structure lithium titanate (Li 2 Ti 3 O 7 ).
- spinel-structured lithium titanate is preferable because of its excellent large current characteristics, life characteristics, and safety.
- the periphery is coated with carbon or a metal oxide.
- Metals and alloys may be ignited by reaction with oxygen in the environment when the particle size is reduced, but safety during material storage can be improved by coating the surroundings with carbon or a ceramic material.
- Covering with carbon is preferable because the conductivity is improved in addition to the improvement in safety and the large current charge / discharge characteristics are improved.
- Covering with a ceramic material is preferable because it becomes a dense protective film and suppresses oxidation of the metal silicon surface. Examples of the ceramic material include oxides, nitrides, borides, phosphides, and sulfides.
- lithium ion conductive ceramics as the ceramic material is preferable because a lithium ion conduction path to metal silicon is ensured.
- the lithium ion conductive ceramics include Li 2 O—SiO 2 type, LiLaZrO type, LiPON type oxide ceramics, Li 2 S—P 2 S 5 type, Li 2 S—SiS 2 type, Sulfide ceramics such as Li 4 GeS 4 -Li 3 PS 4 system, Li 2 S-SiS 2 -Li 4 SiO 4 system, Li 2 S-SiS 2 -Li 3 PO 4 system, Li 2 S-P 2 S Examples thereof include composite ceramics such as 5- P 2 O 5 system.
- Li 2 O—SiO 2 ceramics such as Li 4 SiO 4 is preferable because of its excellent reduction resistance and high strength.
- ceramics such as Al 2 O 3 and TiB 2 are preferable because of excellent durability.
- a conductive material When metal silicon is coated with a ceramic material, it is preferable to add a conductive material.
- a conductive material a metal material, a carbon material, conductive ceramics, or the like can be used.
- a carbon material is preferable because it is lightweight and has high stability with respect to lithium ion conductive glass.
- graphite, VGCF (vapor-grown carbon fiber), and CNT (carbon nanotube) are preferable because they are lightweight and excellent in stability.
- the average particle diameter of the negative electrode active material is, for example, preferably in the range of 1 nm to 100 ⁇ m, and more preferably in the range of 10 nm to 30 ⁇ m. Furthermore, the specific surface area of the particulate negative electrode active material is preferably in the range of, for example, 0.1 m 2 / g or more and 10 m 2 / g or less.
- the negative electrode active material may be used alone or in combination.
- the negative electrode active material may be used singly or as a mixture of a plurality of types, and an organic material active material such as a conductive polymer material or a disulfide polymer material may be mixed.
- the binder of the embodiment is a material having excellent binding properties between the negative electrode active materials and excellent binding properties between the positive electrode active material layer and the current collector.
- a polymer material containing fluorine can be used as the binder. Since the polymer material containing fluorine is excellent in oxidation resistance and reduction resistance, it is possible to provide a cell having excellent life characteristics.
- the binder is at least vinylidene difluoride, tetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, ethylene, tetrafluoroethylene copolymer, hexafluoropropene, polyvinylidene fluoride-hexafluoropropene copolymer as a raw material.
- Fluorine resins using these as raw materials are preferable because they do not dissolve in the electrolyte solution.
- vinylidene difluoride, tetrafluoroethylene, and hexafluoropropene are preferable.
- Specific examples of the fluorine resin include polytetrafluoroethylene. (PTFE), polyvinylidene fluoride (PVdF), polytetrafluoroethylene-vinylidene fluoride (PTFE-PVdF), and polytetrafluoroethylene-hexafluoropropylene (PTFE-HFP).
- PTFE and PVdF are preferable because they are less likely to swell in the non-aqueous electrolyte, and among them, PVdF is preferable because it is easily dissolved in an organic solvent such as N-methylpyrrolidone (NMP).
- NMP N-methylpyrrolidone
- the negative electrode active material layer is a mixture containing a negative electrode active material and a binder, and binds to the current collector.
- a conductive material may be added to the negative electrode active material layer for the purpose of improving the conductivity of the negative electrode.
- the conductive agent can be used without any particular limitation as long as it is a conductive material and does not dissolve during charging.
- the conductive material is not particularly limited as long as it is a conductive material and does not decompose or dissolve when the battery is used.
- carbon materials such as acetylene black, carbon black, graphite, vapor grown carbon fiber (VGCF), and carbon nanotube, metal materials such as aluminum and titanium, conductive ceramic materials, and conductive glass materials can be used.
- a negative electrode active material layer comprising an active material and a binder containing fluorine, wherein the thermal decomposition start temperature of the binder is T1 ° C. and the thermal decomposition end temperature is T2 ° C., the thermal decomposition temperature ( In the pyrolysis gas chromatograph mass spectrometry at T1 + T2) / 2 ° C., there is a peak in the ion chromatogram of any mass number selected from at least 81, 100, 132, 200, and the peak area at the pyrolysis temperature T1 ° C. is X In order to satisfy the condition of 2X ⁇ Y, where the peak area at the thermal decomposition temperature T2 ° C. is Y, the binder is closer to the negative electrode active material than the amount existing far from the negative electrode active material.
- the negative electrode active material layer containing the active material and the binder containing fluorine is preferably one that satisfies the following conditions.
- the thermal decomposition temperature of the binder decreases when it comes into contact with the negative electrode active material.
- the negative electrode active material layer including the active material and the binder containing fluorine is heated, the binder is melted before the main weight reduction occurs.
- the binder in contact with the active material is decomposed and gasified to generate voids.
- the binder that is present in the vicinity of the active material and does not cover the active material melts, moves to the generated void, contacts the active material, and is sequentially decomposed and gasified.
- the binder far from the active material When heated for a long time, the binder far from the active material also moves to the vicinity of the active material due to diffusion, but the binder near the active material and the binder far from the active material can be distinguished by shortening the heating time. Can do. That is, when pyrolysis gas chromatograph mass spectrometry is performed on the basis of the pyrolysis temperature, in addition to the binder covering the negative electrode active material, the binder that does not cover the negative electrode active material and exists nearby The amount can be evaluated, thereby evaluating whether or not the negative electrode active material is in a form that is likely to deteriorate.
- the thermal decomposition temperature can be measured by a thermogravimetric mass spectrometer (TG-MS) that simultaneously performs thermogravimetric analysis and mass analysis of the generated gas.
- TG-MS thermogravimetric mass spectrometer
- the atmosphere during the measurement is not particularly limited as long as it is a non-oxidizing atmosphere, and for example, an inert gas such as helium, argon, or nitrogen can be used.
- the weight reduction process that is excluded when calculating the thermal decomposition temperature is a low-temperature side weight reduction process that releases moisture or carbon dioxide adsorbed when the binder is stored, and can be determined by a TG-MS apparatus.
- the residual weight excluded when calculating the thermal decomposition end temperature is almost no weight loss in an inert gas atmosphere such as carbon and tar components produced by thermal decomposition of the binder, or ceramic materials mixed or added in the manufacturing process. It is derived from a substance that is not observed, and the main weight loss process is observed as a large peak during TG-MS measurement, whereas it can be identified as a broad peak or slope independently of the peak. it can.
- a peak having a small weight reduction process other than the weight reduction process excluded on the low temperature side and the high temperature side is a peak or slope of a change amount of less than 5% by weight of the measurement sample.
- the reference thermal decomposition temperature will be described with reference to the thermogravimetric change graph of PVdF alone which does not contain the active material in FIG.
- TG-MS the temperature at the start and end of thermal decomposition is determined by observing the weight loss of the binder when the temperature is raised from room temperature (25 ° C.) to 1000 ° C.
- PVdF showed a 2% weight loss in the range from room temperature (25 ° C.) to 200 ° C., and no weight loss was observed in the range from 200 ° C. to 400 ° C.
- the weight decreased 3.5% from 400 ° C to 450 ° C, 63% from 450 ° C to 500 ° C, and 3.5% from 500 ° C to 520 ° C, and then gradually decreased. That is, the main weight reduction process in the thermogravimetric analysis of PVdF is in the range of 400 ° C. to 520 ° C., the thermal decomposition temperature T1 is 450 ° C., and the thermal decomposition end T2 is 500 ° C. From this, the binder existing far from the active material is thermally decomposed at T1 (450 ° C.) or more and T2 (500 ° C.) or less, and the binder present near the active material is less than T1 (450 ° C.).
- the pyrolysis time in pyrolysis gas chromatography mass spectrometry is preferably 1 second to 60 seconds. Heating for more than 60 seconds is not preferable because the binder far from the active material moves to the vicinity of the active material by diffusion.
- FIG. 3 shows ion chromatograms having mass numbers of 132 and 200 in pyrolysis gas chromatograph mass spectrometry heated at 475 ° C. for 30 seconds corresponding to (T1 + T2) / 2.
- T1 + T2 pyrolysis gas chromatograph mass spectrometry
- a binder containing fluorine has a signal of at least one of the mass numbers 81, 100, 132, and 200, depending on the compound constituting the binder, when pyrolysis mass spectrometry is performed. .
- an ion chromatogram obtained by extracting signals of mass numbers 81, 100, 132, and 200 specific to the binder containing fluorine by the pyrolysis gas chromatograph mass spectrometer is used. From the ion chromatogram, the area of the amount of the binder present in the vicinity of the negative electrode active material and the area of the amount of the binder present in the distance of the negative electrode active material are calculated.
- the thermal decomposition start temperature of the binder is T1 ° C. and the thermal decomposition end temperature is T2 ° C.
- the signal of the mass number having the maximum signal area is used.
- the signal area with the mass number 132 is the largest, the signal area with the mass number of 132 is obtained even in the measurement of the negative electrode active material layer.
- X be the peak area of the ion chromatograph with mass number 132 at the thermal decomposition temperature T1 ° C.
- Y be the peak area of the ion chromatograph with mass number 132 at the thermal decomposition temperature T2 ° C.
- PVdF is used as the binder, so the area of the signal having the mass number 132 is obtained.
- the binder is PTFE, the mass such as the mass number 81 is obtained.
- X and Y can be obtained from a number of signal areas.
- the amount of the binder near the active material is far from the active material. It represents more than the amount of binder.
- 2X ⁇ Y the mechanism for improving the discharge capacity as described above is not necessarily clear, but is estimated as follows. In the charged state, the active material has high reaction activity, and the binding material reacts with the active material, so that the binding strength between the active material and the conductive material is weakened, and the capacity may be reduced. In this case, it is presumed that the conductivity is maintained by maintaining the binding force by increasing the binder near the active material.
- the binder existing between the active material and the conductive material is swollen by the organic solvent constituting the non-aqueous electrolyte, the binding force between the active material and the conductive material is reduced, and the capacity is reduced as the resistance is increased. there's a possibility that. Also in this case, it is presumed that the conductivity is maintained by maintaining the binding force by increasing the binder near the active material. Moreover, since the binder between two adjacent conductive material particles decreases by increasing the binder near the active material, it is presumed that the increase in resistance due to the binder swelling is suppressed.
- a binder that is not in contact with the negative electrode active material in the initial state that is, does not cover the active material and is present in the vicinity does not contribute to the binding force between the active material and the conductive material at first,
- the volume increases, and it is estimated that the binding force between the active material and the conductive material is increased.
- the mixing ratio of the negative electrode active material, the binder, and the conductive material is 80% by mass to 95% by mass of the negative electrode active material, 3% by mass to 18% by mass of the conductive material, and 2% by mass of the binder. It is preferable that it is 17 mass% or less.
- the conductive material is added in an amount of 3% by mass or more, the effect of improving the conductivity can be exhibited, and by setting the conductive material to 18% by mass or less, the discharge capacity can be prevented from falling below the practical range.
- the binder is added in an amount of 2% by mass or more, sufficient binding strength can be obtained, and by making the amount 17% by mass or less, it is possible to prevent the large current discharge characteristics from falling below the practical range due to the decrease in conductivity. it can.
- a non-porous metal foil As the current collector of the embodiment, a non-porous metal foil, a punched metal having a large number of holes, a metal mesh formed from a fine metal wire, or the like can be used.
- the material of the current collector is not particularly limited as long as it does not dissolve in the battery usage environment.
- a metal such as Al or Ti, or the above-mentioned metal as a main component, Zn, Mn, Fe, Cu, Si
- copper foil is particularly preferable because it is flexible and has excellent moldability.
- the negative electrode is produced by mixing a negative electrode active material, a binder, and a conductive material and supporting them on the surface of the current collector.
- the negative electrode active material, the binder and the conductive material can be suspended in a suitable solvent, and the obtained suspension can be applied to Cu foil, dried and pressed.
- it can produce by mixing a negative electrode active material, a binder, and a electrically conductive material in a solid state, press-bonding the obtained mixture to a nickel mesh, drying, and pressing.
- the method of suspending a negative electrode active material, a binder, and a conductive material in an organic solvent such as NMP is preferable because a homogeneous electrode can be formed.
- the electrode of the embodiment can be obtained by increasing the amount of the binder near the active material in the manufacturing process.
- the binder and the negative electrode active material are first kneaded, and then the conductive material is added and kneaded.
- the kneading energy after adding the conductive material is preferably smaller than the energy for kneading the binder and the negative electrode active material.
- the kneading energy is controlled by changing the operating conditions of the kneading apparatus or by changing the apparatus itself.
- the operating conditions can include time, temperature, rotational speed of the kneading blade / container, etc., and increasing the energy can be achieved by extending the kneading time, increasing the kneading temperature, and increasing the rotational speed of the kneading blade / container.
- Examples of the change of the apparatus include addition of beads for stirring, change to an apparatus corresponding to stirring in the presence of beads.
- the beads are ceramics or metallic spheres having a size of about 1 mm to 3 cm, and the solid agglomerates can be broken by adding them during kneading.
- the nonaqueous electrolyte secondary battery according to the second embodiment includes a positive electrode, a negative electrode, a nonaqueous electrolyte layer formed between the positive electrode and the negative electrode, and a case that accommodates the positive electrode, the negative electrode, and the electrolyte.
- FIG. 5 is a conceptual cross-sectional view of a flat type nonaqueous electrolyte secondary battery 200 in which the bag-shaped exterior material 202 is made of a laminate film.
- the flat wound electrode group 201 is housed in a bag-like exterior material 202 made of a laminate film in which an aluminum foil is interposed between two resin layers.
- a flat wound electrode group 201 is laminated in the order of a negative electrode 203, a separator 204, a positive electrode 205, and a separator 204 as shown in FIG. And it is formed by winding the laminate in a spiral shape and press-molding it.
- the electrode closest to the bag-shaped exterior material 202 is a negative electrode, and this negative electrode has no negative electrode active material layer formed on the negative electrode current collector on the bag-shaped exterior material 202 side.
- the negative electrode active material layer is formed only on one side of the side.
- the other negative electrode 203 is configured by forming a negative electrode active material layer on both surfaces of a negative electrode current collector.
- the positive electrode 205 is configured by forming a positive electrode active material layer on both surfaces of a positive electrode current collector.
- the negative electrode terminal is electrically connected to the negative electrode current collector of the outermost negative electrode 203
- the positive electrode terminal is electrically connected to the positive electrode current collector of the inner positive electrode 205.
- the negative electrode terminal 206 and the positive electrode terminal 207 extend to the outside from the opening of the bag-shaped exterior material 202.
- the liquid non-aqueous electrolyte is injected from the opening of the bag-shaped exterior material 202.
- the wound electrode group 201 and the liquid nonaqueous electrolyte are completely sealed by heat-sealing the opening of the bag-shaped exterior material 202 with the negative electrode terminal 206 and the positive electrode terminal 207 interposed therebetween.
- the negative electrode terminal examples include aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si.
- the negative electrode terminal is preferably made of the same material as the negative electrode current collector.
- a material having electrical stability and conductivity in a range where the potential with respect to the lithium ion metal is 3 V or more and 4.25 V or less can be used.
- aluminum or an aluminum alloy containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si can be given.
- the positive electrode terminal is preferably made of the same material as that of the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.
- the bag-shaped exterior material, the positive electrode, the negative electrode, the electrolyte, and the separator which are constituent members of the nonaqueous electrolyte secondary battery, will be described in detail.
- Bag-shaped exterior material The bag-shaped exterior material is formed from a laminate film having a thickness of 0.5 mm or less. Alternatively, a metal container having a thickness of 1.0 mm or less is used as the exterior material. The metal container is more preferably 0.5 mm or less in thickness.
- the shape of the bag-shaped exterior material can be selected from a flat type (thin type), a square type, a cylindrical type, a coin type, and a button type.
- the exterior material include, for example, an exterior material for a small battery that is loaded on a portable electronic device or the like, an exterior material for a large battery that is loaded on a two- to four-wheeled vehicle, etc., depending on the battery size.
- the laminate film a multilayer film in which a metal layer is interposed between resin layers is used.
- the metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction.
- a polymer material such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used.
- PP polypropylene
- PE polyethylene
- PET polyethylene terephthalate
- the laminate film can be molded into the shape of an exterior material by sealing by heat sealing.
- Metal containers are made from aluminum or aluminum alloy.
- the aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon.
- transition metals such as iron, copper, nickel, and chromium are included in the alloy, the amount is preferably 100 ppm by mass or less.
- Negative electrode As the negative electrode, the positive electrode of the first embodiment is used.
- a positive electrode is a positive electrode in connection with this embodiment, as a negative electrode active material and a binder, if it is a compound used as a nonaqueous electrolyte secondary battery, it will not specifically limit.
- Positive electrode A positive electrode is produced by mixing a positive electrode active material, a binder, and a conductive material and supporting the mixture on the surface of a current collector.
- the positive electrode active material, the binder and the conductive material can be suspended in a suitable solvent, and the obtained suspension can be applied to an Al alloy foil, dried and pressed.
- it can produce by mixing a positive electrode active material, a binder, and a electrically conductive material in a solid state, press-bonding the obtained mixture to an Al alloy mesh, drying, and pressing.
- the method of suspending the positive electrode active material, the binder, and the conductive material in an organic solvent such as NMP is preferable because a homogeneous electrode can be formed.
- the positive electrode active material of the embodiment performs insertion and extraction of Li.
- the positive electrode active material is not particularly limited as long as it is a positive electrode active material used as a nonaqueous electrolyte secondary battery, and can be used.
- a lithium composite oxide containing lithium and a metal other than lithium a lithium composite phosphate compound, a conductive polymer such as polyaniline or polypyrrole, a disulfide polymer containing sulfur, or a fluorocarbon can be used. .
- Examples of the metal other than lithium contained in the composite oxide containing lithium and a metal other than lithium include one or more metals selected from Fe, Ni, Co, Mn, V, Al, and Cr.
- the complex oxide containing Mn for example, LiMn 2 O 4, Li (1 + x) Mn (2-x-y) M y O z (0 ⁇ x ⁇ 0.2,0 ⁇ y ⁇ 1.1,3. 9 ⁇ z ⁇ 4.1, where M is at least one element selected from Ni, Co, and Fe).
- Examples of the composite oxide containing V or Cr include LiVO 2 and LiCrO 2 .
- a positive electrode active material having a charge end voltage of 4.0 V or higher with respect to a lithium potential reference (hereinafter referred to as (Li / Li +)) is preferable because the effect of this embodiment is large.
- a complex oxide containing Mn LiMn 2 O 4 , Li (1 + x) Mn (2-xy) M y O z (0 ⁇ x ⁇ 0.2, 0 ⁇ y ⁇ 1.1, 3 .9 ⁇ z ⁇ 4.1, where M is at least one element selected from Ni, Co, and Fe), and more specifically, LiMn 1.5 Ni 0.5 O 4 , LiMn 1 .5 Co 0.5 O 4 , LiMnFeO 4 , LiMn 1.5 Fe 0.5 O 4 , LiMnCoO 4 is replaced by Li (Ni 1/3 Co 1/3 Mn 1/3 ) O 2 or the like, Li (Ni 5 / 10 Co 2/10 Mn 3/10 ) O 2 , Li (Ni 6/10 Co 2/10
- Li (Ni x M y ) O 2 (x + y 1, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, M is at least one selected from Co and Al) More specifically, LiNiO 2 , LiCo 0.5 Ni 0.5 O 2 , LiNi 0.9 Al 0.1 O 2 , LiNi 0.8 Co 0.1 Al 0. 1 O 2 etc. can be mentioned.
- the positive electrode active material charge voltage is not less than 4.8V with respect to Li / Li + is preferred for effectively is particularly large in this embodiment, as is specifically lithium composite oxide Li (1 + x ) Mn (2-x-y ) M y O z (0 ⁇ x ⁇ 0.2,0 ⁇ y ⁇ 1.1,3.9 ⁇ z ⁇ 4.1, M is selected Ni, Co, from Fe At least one element), and more specifically, LiMn 1.5 Ni 0.5 O 4 , LiMn 1.5 Co 0.5 O 4 , LiMnFeO 4 , LiMn 1.5 Fe 0.5 O 4 , LiMnCoO 4 , Li (Ni 1 / 3 Co 1/3 Mn 1/3 ) O 2 , Li (Ni 5/10 Co 2/10 Mn 3/10 ) O 2 , Li (Ni 6/10 Co 2/10 Mn 2/10 ) O 2 , Li (Ni 8/10 Co 1/10 Mn 1/10 ) O 2 can be mentioned.
- the shape of the positive electrode active material is preferably particulate.
- the average particle diameter of the particulate positive electrode active material is preferably in the range of, for example, 1 nm to 100 ⁇ m, and more preferably in the range of 10 nm to 30 ⁇ m.
- the specific surface area of the particulate positive electrode active material is preferably in the range of, for example, 0.1 m 2 / g or more and 10 m 2 / g or less.
- the positive electrode active material may be used singly or as a mixture of a plurality of types, and an organic material active material such as a conductive polymer material or a disulfide polymer material may be mixed therein.
- the binder of the embodiment is a material that is excellent in binding property between the positive electrode active materials and excellent in binding property between the positive electrode active material layer and the current collector.
- a polymer material containing fluorine can be used as the binder. Since the polymer material containing fluorine is excellent in oxidation resistance and reduction resistance, it is possible to provide a cell having excellent life characteristics.
- the binder is at least vinylidene difluoride, tetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, ethylene, tetrafluoroethylene copolymer, hexafluoropropene, polyvinylidene fluoride-hexafluoropropene copolymer as a raw material.
- Fluorine resins using these as raw materials are preferable because they do not dissolve in the electrolyte solution.
- vinylidene difluoride, tetrafluoroethylene, and hexafluoropropene are preferable.
- Specific examples of the fluorine resin include polytetrafluoroethylene. (PTFE), polyvinylidene fluoride (PVdF), polytetrafluoroethylene-vinylidene fluoride (PTFE-PVdF), and polytetrafluoroethylene-hexafluoropropylene (PTFE-HFP).
- PTFE and PVdF are preferable because they are less likely to swell in the non-aqueous electrolyte, and among them, PVdF is preferable because it is easily dissolved in an organic solvent such as N-methylpyrrolidone (NMP).
- NMP N-methylpyrrolidone
- the conductive material can be used without any particular limitation as long as it is a conductive material and does not dissolve during charging.
- carbon materials such as acetylene black, carbon black, and graphite, metal materials such as copper, aluminum, stainless steel, and titanium, conductive ceramic materials, and conductive glass materials can be used.
- acetylene black is used as the positive electrode conductive material.
- carbon materials such as carbon black and graphite, metal powder materials selected from aluminum and titanium, conductive ceramic materials, and conductive glass materials can be used.
- the mixing ratio of the negative electrode active material, the binder, and the binder is 70% by mass to 95% by mass of the negative electrode active material, 0% by mass to 25% by mass of the conductive material, 2% by mass of dressing It is preferable to be in the range of 10% by mass or less.
- the current collector can be used without any particular limitation as long as it is a conductive material that does not deteriorate, dissolve, or deform when the battery is used.
- a conductive material that does not deteriorate, dissolve, or deform when the battery is used.
- foil, mesh, punched metal, or lath metal made of copper, stainless steel, or nickel can be used.
- Electrolyte A nonaqueous electrolyte is prepared by dissolving an electrolyte in a nonaqueous solvent.
- non-aqueous solvents examples include esters, carbonates, and sulfonate compounds.
- At least one non-aqueous solvent selected from ethylene carbonate, propylene carbonate, and ⁇ -butyrolactone and at least one non-aqueous solvent selected from ethyl methyl carbonate, diethyl carbonate, and dimethyl carbonate are mixed and used. It is preferable.
- ethylene carbonate, propylene carbonate, ethyl methyl carbonate, and ⁇ -butyrolactone are preferable.
- the aliphatic carboxylic acid ester when included, it is preferably 30% by weight or less, more preferably 20% by weight or less of the whole non-aqueous solvent.
- the non-aqueous solvent of the embodiment for example, any of the following compositions is preferable.
- Nonaqueous solvent 1 100% by volume of a non-aqueous solvent comprising 5% to 50% by volume of ethylene carbonate and 50% to 95% by volume of ethyl methyl carbonate.
- Nonaqueous solvent 2 100% by volume of a non-aqueous solvent comprising 5% to 50% by volume of ethylene carbonate and 50% to 95% by volume of diethyl carbonate.
- Nonaqueous solvent 3 A total of 100% by volume of a nonaqueous solvent comprising 5% to 40% by volume of ethylene carbonate, 20% to 80% by volume of propylene carbonate, and 5% to 40% by volume of ⁇ -butyrolactone.
- chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate are used for the purpose of reducing the viscosity
- cyclic carbonates such as ethylene carbonate are used for the purpose of increasing the dielectric constant.
- Esters may be added. It is preferable that at least one selected from the group consisting of a carbonate ester-based additive and a sulfur compound-based additive is added to the non-aqueous electrolyte from the viewpoint of further improving the effect of suppressing gas generation. .
- Carbonate-based additives have the effect of reducing gases such as H 2 and CH 4 generated on the negative electrode surface by film formation and the like, and sulfur compound-based additives are generated on the positive electrode surface by film formation and the like. It believed to have the effect of reducing the gas, such as CO 2.
- Examples of the carbonate-based additive include vinylene carbonate, phenylethylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, trifluoropropylene carbonate, chloroethylene carbonate, methoxypropylene carbonate, vinylethylene carbonate, catechol carbonate, tetrahydrofuran carbonate, diphenyl carbonate, Examples include diethyl dicarbonate (diethyl dicarbonate). These may be used alone or in combination of two or more. Among these, vinylene carbonate, phenyl vinylene carbonate, and the like are preferable, and vinylene carbonate is particularly preferable in that the effect of reducing the gas generated on the negative electrode surface is large.
- sulfur compound-based additive examples include ethylene sulfite, ethylene trithiocarbonate, vinylene trithiocarbonate, catechol sulfite, tetrahydrofuran sulfite, sulfolane, 3-methylsulfolane, sulfolene, propane sultone, 1,4-butane sultone, etc. Is mentioned. These may be used alone or in combination of two or more. Among these, propane sultone, sulfolane, ethylene sulfite, catechol sulfite, and the like are preferable, and propane sultone is particularly preferable in that the effect of reducing the gas generated on the surface of the positive electrode is large.
- the addition ratio with respect to 100 parts by mass of at least one non-aqueous electrolyte selected from the group consisting of a carbonate ester-based additive and a sulfur compound-based additive is 0.1 to 10 parts by mass in total, and more preferably 0. It is preferably 5 parts by mass or more and 5 parts by mass or less.
- the addition ratio is 1: 9 to 9: 1. Is preferable in that it can be obtained with good balance.
- the addition ratio with respect to 100 parts by mass of the nonaqueous electrolyte is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 5 parts by mass or less.
- the addition ratio is less than 0.1 parts by mass, the effect of reducing the amount of gas generated in the negative electrode is reduced, and when it exceeds 10 parts by mass, the film formed on the electrode becomes too thick and the discharge characteristics deteriorate.
- the addition ratio with respect to 100 parts by mass of the nonaqueous electrolyte is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 5 parts by mass or less.
- the addition ratio is less than 0.1 parts by mass, the effect of reducing the amount of gas generated in the positive electrode is reduced, and when it exceeds 10 parts by mass, the coating formed on the electrode becomes too thick and the discharge characteristics deteriorate.
- an alkali salt can be used as the electrolyte contained in the nonaqueous electrolytic solution.
- lithium salt is used.
- the lithium salt LiPF 4 (CF 3) 2 , LiPF 4 (C2F 5) 2, LiPF 3 (CF 3) 3, LiPF 3 (C 2 F 5) 3, LiPF 4 (CF 3 SO 2) 2, LiPF 4 (C 2 F 5 SO 2 ) 2 , LiPF 3 (CF 3 SO 2 ) 3 , LiPF 3 (C 2 F 5 SO 2 ) 3 , LiBF 2 (CF 3 ) 2 , LiBF 2 (C 2 F 5 ) 2, LiBF 2 (CF 3 SO 2) containing 2, LiBF 2 (C 2 F 5 SO 2) 2, LiPF 6, LiBF 4, LiSbF 6, at least one electrolyte salt selected from the group consisting of LiAsF 6 It is preferable.
- the above compounds are extremely excellent in thermal stability, so there is little deterioration in battery characteristics during high temperature use or after storage at high temperatures, and there is little gas generation due to thermal decomposition, but these compounds are susceptible to decomposition reactions on the positive electrode. There is a problem. Therefore, when LiPF 6, LiBF 4, LiSbF 6 , is contained at least one electrolyte salt selected from the group consisting of LiAsF 6, these salts react preferentially with the positive electrode, good coating on the positive electrode As a result, the decomposition reaction of the above compound on the positive electrode is suppressed.
- a separator can be used when a non-aqueous electrolyte is used and when an electrolyte-impregnated polymer electrolyte is used.
- a porous separator is used as the separator.
- the separator is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. It may be.
- the thickness of the separator is preferably 30 ⁇ m or less. If the thickness exceeds 30 ⁇ m, the distance between the positive and negative electrodes may be increased and the internal resistance may be increased. Further, the lower limit value of the thickness is preferably 5 ⁇ m. If the thickness is less than 5 ⁇ m, the strength of the separator is remarkably lowered and an internal short circuit is likely to occur.
- the upper limit value of the thickness is more preferably 25 ⁇ m, and the lower limit value is more preferably 1.0 ⁇ m.
- the separator preferably has a heat shrinkage rate of 20% or less when kept at 120 ° C. for 1 hour. If the heat shrinkage rate exceeds 20%, the possibility of a short circuit due to heating increases. The thermal shrinkage rate is more preferably 15% or less.
- the separator preferably has a porosity in the range of 30% to 70%. This is due to the following reason. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator. On the other hand, if the porosity exceeds 60%, sufficient separator strength may not be obtained. A more preferable range of the porosity is 35% or more and 70% or less.
- the separator preferably has an air permeability of 500 seconds / 1.00 cm 3 or less. If the air permeability exceeds 500 seconds / 1.00 cm 3 , it may be difficult to obtain high lithium ion mobility in the separator 204.
- the lower limit of the air permeability is 30 seconds / 1.00 cm 3 . This is because if the air permeability is less than 30 seconds / 1.00 cm 3 , sufficient separator strength may not be obtained.
- the upper limit value of the air permeability is more preferably 300 seconds / 1.00 cm 3 , and the lower limit value is more preferably 50 seconds / 1.00 cm 3 .
- the battery pack according to the third embodiment includes one or more non-aqueous electrolyte secondary batteries (that is, single cells) according to the second embodiment.
- the battery pack includes a plurality of single cells, the single cells are electrically connected in series, parallel, or connected in series and parallel.
- the battery pack 300 will be specifically described with reference to the conceptual diagram of FIG. 7 and the block diagram of FIG. In the battery pack 300 shown in FIG. 7, the flat nonaqueous electrolyte battery 200 shown in FIG. 5 is used as the unit cell 301.
- the plurality of single cells 301 are stacked such that the negative electrode terminal 302 and the positive electrode terminal 303 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 304 to constitute an assembled battery 305. These unit cells 301 are electrically connected to each other in series as shown in FIG.
- the printed wiring board 306 is disposed to face the side surface of the unit cell 301 from which the negative electrode terminal 302 and the positive electrode terminal 303 extend. As shown in FIG. 8, a thermistor 307, a protection circuit 308, and a terminal 309 for energizing external devices are mounted on the printed wiring board 306. Note that an insulating plate (not shown) is attached to the surface of the protection circuit board 306 facing the assembled battery 305 in order to avoid unnecessary connection with the wiring of the assembled battery 305.
- the positive electrode side lead 310 is connected to the positive electrode terminal 303 located at the lowermost layer of the assembled battery 305, and the tip thereof is inserted into the positive electrode side connector 311 of the printed wiring board 306 and electrically connected thereto.
- the negative electrode side lead 312 is connected to the negative electrode terminal 302 located on the uppermost layer of the assembled battery 305, and the tip thereof is inserted into and electrically connected to the negative electrode side connector 313 of the printed wiring board 306.
- These connectors 311 and 313 are connected to the protection circuit 308 through wirings 314 and 315 formed on the printed wiring board 306.
- the thermistor 307 is used to detect the temperature of the unit cell 305, and the detection signal is transmitted to the protection circuit 308.
- the protection circuit 308 can cut off the plus-side wiring 316a and the minus-side wiring 316b between the protection circuit 308 and the terminal 309 for energizing external devices under a predetermined condition.
- the predetermined condition is, for example, when the temperature detected by the thermistor 307 is equal to or higher than a predetermined temperature.
- the predetermined condition is when an overcharge, overdischarge, overcurrent, or the like of the unit cell 301 is detected. This detection of overcharge or the like is performed for each single cell 301 or the entire single cell 301.
- the battery voltage When detecting each single cell 301, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 301. 5 and 6, a voltage detection wiring 317 is connected to each single cell 301, and a detection signal is transmitted to the protection circuit 308 through the wiring 317.
- a protective sheet 318 made of rubber or resin is disposed on each of the three side surfaces of the assembled battery 305 excluding the side surface from which the positive electrode terminal 303 and the negative electrode terminal 302 protrude.
- the assembled battery 305 is stored in the storage container 319 together with each protective sheet 318 and the printed wiring board 306. That is, the protective sheet 318 is disposed on each of the inner side surface in the long side direction and the inner side surface in the short side direction of the storage container 319, and the printed wiring board 306 is disposed on the inner side surface on the opposite side in the short side direction.
- the assembled battery 305 is located in a space surrounded by the protective sheet 318 and the printed wiring board 306.
- the lid 320 is attached to the upper surface of the storage container 319.
- a heat shrink tape may be used for fixing the assembled battery 305.
- protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the assembled battery.
- FIG. 7 and 8 show the configuration in which the single cells 301 are connected in series, but in order to increase the battery capacity, they may be connected in parallel, or a combination of series connection and parallel connection may be used.
- the assembled battery packs can be further connected in series and in parallel. According to this embodiment described above, it is possible to provide a battery pack having excellent charge / discharge cycle performance by including the nonaqueous electrolyte secondary battery having excellent charge / discharge cycle performance in the third embodiment. it can.
- the aspect of a battery pack is changed suitably according to a use.
- the battery pack is preferably one that exhibits excellent cycle characteristics when a large current is taken out.
- Specific examples include a power source for a digital camera, a vehicle for a two- to four-wheel hybrid electric vehicle, a two- to four-wheel electric vehicle, an assist bicycle, and the like.
- a battery pack using a nonaqueous electrolyte secondary battery having excellent high temperature characteristics is suitably used for in-vehicle use.
- Example 1 PVdF was used as the binder.
- the thermal decomposition temperature T1 was 450 ° C.
- the thermal decomposition end temperature T2 was 500 ° C.
- fragments with mass numbers 132 and 200 were present.
- a negative electrode was prepared using Li 4 Ti 5 O 12 as the active material, PVdF as the binder, and acetylene black as the conductive material, with a composition ratio of 80: 5: 15 by weight.
- PVdF was dissolved in NMP so as to be 10% by weight, charged into a ball mill together with the negative electrode active material, and stirred for 4 hours to prepare a negative electrode active material paste.
- the prepared paste was taken out from the ball mill, the balls were removed, and the paste was put together with acetylene black in a stirring vessel equipped with two stirring blades, and stirred at room temperature for 30 minutes to prepare a negative electrode slurry.
- the prepared negative electrode slurry was applied on a copper foil using an applicator, dried at 130 ° C. under atmospheric pressure, and then vacuum dried at 150 ° C. to prepare a negative electrode.
- the prepared active material layer of the negative electrode was shaved and analyzed by a pyrolyzate gas chromatograph mass spectrometer. As a result, peaks were present in ion chromatograms of mass numbers 132 and 200 at a pyrolysis temperature of 475 ° C., and mass number 132 Gave the largest area.
- X and Y have a relationship of 2X ⁇ Y.
- Example 2 Using the obtained negative electrode, a positive electrode made of LiFePO 4 , and a non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was prepared, and a charge / discharge cycle test was performed at 60 ° C. As a result, the capacity retention rate after 2,000 cycles was 98%.
- Example 2 The negative electrode was prepared in the same manner as in Example 1 except that silicon powder was used as the active material, graphite was used as the conductive material, and the composition ratio of the active material, the binder, and the conductive material was 75: 20: 5 by weight. A non-aqueous electrolyte secondary battery was prepared and a charge / discharge cycle test was conducted.
- X and Y had a relationship of 2X ⁇ Y.
- the capacity retention after 50 cycles was 80%.
- Example 3 A negative electrode and a nonaqueous electrolyte secondary battery were prepared in the same manner as in Example 2 except that a silicon / silicon oxide / carbon composite material was used as the active material, and a charge / discharge cycle test was performed.
- X and Y had a relationship of 2X ⁇ Y.
- the capacity retention rate after 30 cycles was 80%.
- the silicon / silicon oxide / carbon composite material was obtained by mixing and firing silicon monoxide and a carbon precursor and then pulverizing them.
- Example 4 A negative electrode and a nonaqueous electrolyte secondary battery were prepared in the same manner as in Example 2 except that silicon nanotubes were used as the active material, and a charge / discharge cycle test was performed. X and Y had a relationship of 2X ⁇ Y. In the charge / discharge cycle test, the capacity retention rate after 100 cycles was 80%.
- Example 5 A positive electrode was prepared in the same manner as in Example 1 except that Li (Ni 5/10 Co 2/10 Mn 3/10 ) O 2 was used as the active material.
- a non-aqueous electrolyte secondary battery was prepared, and a charge / discharge cycle test was performed in the same manner as in Example 1.
- X and Y had a relationship of 2X ⁇ Y.
- the capacity retention rate after 300 cycles was 90%.
- Example 6 A positive electrode and a nonaqueous electrolyte secondary battery were prepared in the same manner as in Example 5 except that LiMn 1.5 Ni 0.5 O 4 was used as the active material, and a charge / discharge cycle test was performed.
- X and Y had a relationship of 2X ⁇ Y.
- the capacity retention rate after 200 cycles was 80%.
- Example 7 A positive electrode and a non-aqueous electrolyte secondary battery were prepared in the same manner as in Example 5 except that Li (Fe 0.4 Mn 0.6 ) PO 4 was used as the positive electrode active material, and a charge / discharge cycle test was performed. did. X and Y had a relationship of 2X ⁇ Y. The capacity retention rate after 200 cycles was 85%.
- a negative electrode was prepared using Li 4 Ti 5 O 12 as the active material, PVdF as the binder, and acetylene black as the conductive material, with a composition ratio of 80: 5: 15 by weight.
- PVdF was dissolved in NMP so as to be 10% by weight, put into a ball mill together with a conductive material, and stirred for 4 hours to prepare a negative electrode active material paste.
- the prepared paste was taken out from the ball mill, the balls were removed, and the paste was put together with the active material into a stirring vessel equipped with two stirring blades, and stirred at room temperature for 30 minutes to prepare a negative electrode slurry.
- the prepared negative electrode slurry was applied on a copper foil using an applicator, dried at 130 ° C.
- a negative electrode under atmospheric pressure, and then vacuum dried at 150 ° C. to prepare a negative electrode.
- the prepared active material layer of the negative electrode was shaved and analyzed by a pyrolyzate gas chromatograph mass spectrometer. As a result, peaks were present in ion chromatograms of mass numbers 132 and 200 at a pyrolysis temperature of 475 ° C., and mass number 132 Gave the largest area.
- X and Y have a relationship of 2X ⁇ Y.
- a positive electrode made of LiFePO 4 , and a non-aqueous electrolyte a non-aqueous electrolyte secondary battery was prepared, and a charge / discharge cycle test was performed at 60 ° C. As a result, the capacity retention rate after 2,000 cycles was 90%.
- Comparative Example 2 The negative electrode was prepared in the same manner as in Comparative Example 1 except that silicon powder was used as the active material, graphite was used as the conductive material, and the composition ratio of the active material, the binder, and the conductive material was 75: 20: 5 by weight.
- a non-aqueous electrolyte secondary battery was prepared and a charge / discharge cycle test was conducted. X and Y had a relationship of 2X ⁇ Y. In the charge / discharge cycle test, the capacity retention rate after 50 cycles was 65%.
- Comparative Example 3 A negative electrode and a nonaqueous electrolyte secondary battery were prepared in the same manner as in Comparative Example 2 except that a silicon / silicon oxide / carbon composite material was used as the active material, and a charge / discharge cycle test was performed. X and Y had a relationship of 2X ⁇ Y. In the charge / discharge cycle test, the capacity retention rate after 30 cycles was 75%.
- the silicon / silicon oxide / carbon composite material was obtained by mixing and firing silicon monoxide and a carbon precursor and then pulverizing them.
- Comparative Example 4 A negative electrode and a non-aqueous electrolyte secondary battery were prepared in the same manner as in Comparative Example 2 except that silicon nanotubes were used as the active material, and a charge / discharge cycle test was performed. X and Y had a relationship of 2X ⁇ Y. In the charge / discharge cycle test, the capacity retention rate after 100 cycles was 60%.
- Comparative Example 5 A positive electrode was prepared in the same manner as in Comparative Example 1 except that Li (Ni 5/10 Co 2/10 Mn 3/10 ) O 2 was used as the active material. Using the obtained positive electrode, a negative electrode made of graphite, and a non-aqueous electrolyte, a non-aqueous electrolyte secondary battery was prepared, and a charge / discharge cycle test was performed in the same manner as in Example 1. X and Y had a relationship of 2X ⁇ Y. The capacity retention rate after 300 cycles was 70%.
- Comparative Example 6 A positive electrode and a nonaqueous electrolyte secondary battery were prepared in the same manner as in Comparative Example 5 except that LiMn 1.5 Ni 0.5 O 4 was used as the active material, and a charge / discharge cycle test was performed. X and Y had a relationship of 2X ⁇ Y. The capacity retention rate after 200 cycles was 60%.
- Comparative Example 7 A positive electrode and a non-aqueous electrolyte secondary battery were prepared in the same manner as in Comparative Example 5 except that Li (Fe 0.4 Mn 0.6 ) PO 4 was used as the positive electrode active material, and a charge / discharge cycle test was performed. did. X and Y had a relationship of 2X ⁇ Y. The capacity retention rate after 200 cycles was 75%. As described above, according to the present invention, a non-aqueous electrolyte secondary battery having an excellent capacity retention rate could be produced.
Abstract
Description
非水電解質二次電池が充放電を繰り返す間に劣化する反応機構は、必ずしも明確とはなっていないが、例えば、以下のような反応機構が提案されている。
にて分析した際、主となる重量減少過程において、重量減少過程における重量減少分の5%が減少する温度であり、結着材の熱分解終了温度とは、結着材を熱重量分析装置にて分析した際、主となる重量減少過程において、重量減少過程における重量減少分の95%が減少する温度であり、ピーク面積とは、結着材単体の熱分解温度(T1+T2)/2℃における熱分解ガスクロマトグラフ質量分析において、質量数81、100、132、200で抽出したイオンクロマトグラフのうち、最大の面積を与える質量数のピーク面積である。
(第1実施形態)
本実施形態に係る第1実施形態として電極が負極である場合を例に以下説明する。
図1の概念図に示すように、第1実施形態の負極100は、負極活物質101と、負極活物質101を結着する結着材102とを含む層状の負極活物質層103と、負極活物質層103と結着した集電体104と、を有する。負極極活物質層103は集電体104の片面又は両面に形成されている。以下、図面を参照する場合を除いて、符号は省略する。
繊維状金属シリコンとしては、直径1μm以下、長さ20μm以下のものが好ましい。直径1μmを超えると充放電時の体積膨張収縮により微粉化する可能性があり、長さが20μmを超えるとセパレータを貫通して正負極間で短絡する恐れがある。なかでも、直径300nm以下の繊維状金属シリコンは、充放電時の体積膨張による微粉化を抑制できるために好ましい。特に、螺旋状の高次構造を有する繊維状金属シリコンは、充放電時の体積膨張収縮による繊維長変化を抑制できるために好ましい。また、繊維形状としては、コイル状の高次構造を有していると、充放電時の体積膨張収縮による集電体金属箔からの脱離が抑制されるために好ましい。
燐片状金属シリコンとしては、一辺の長さ10μm以下、厚さ2μm以下のものが好ましい。一辺の長さが10μmを超えるか、あるいは厚さが2μmを超えると、充放電時の体積膨張収縮により微粉化する可能性がある。
合金状態のシリコンとしては、例えば、マグネシウム、鉄、ニッケル、銅、チタンとの合金を挙げることができる。具体的には、例えば、マグネシウム合金系としてはMg2Si系、鉄系合金としてはFeSi4系、ニッケル合金系としてはSiNi系、銅合金系としてはSiCu系、チタン合金系としてはTiSi3系を挙げることができる。また、FeCuSi系のように3種類以上の合金を用いてもよい。なかでも、Mg2Si系合金、FeSi4系合金、SiNi系合金は放電容量が大きいために好ましい
合金状態のスズとしては、例えば、マグネシウム、アンチモン、鉄、コバルト、ニッケル、銅、銀、セリウム、ランタノイドとの合金を挙げることができる。なかでも、コバルト、アンチモン、鉄、銀との合金が、放電容量が大きいためにこのましい。
セラミクスのスズとしては、例えば、リン化物、酸化物を挙げることができる。なかでもリン化物は、放電容量が大きいために好ましい。
金属元素としてアンチモンを含む場合、金属あるいは合金の形態が好ましい。合金としては、例えばインジウム、チタン、マグネシウム、コバルト、ニッケル、銀、アルミニウム、鉄、マンガンとの合金を挙げることができる。
負極は、負極活物質、結着材および導電材を混合し、集電体表面に担持することにより作製される。例えば、負極活物質、結着材および導電材を適当な溶媒に懸濁させ、得られた懸濁物をCu箔に塗布し、乾燥し、プレスすることにより作製することができる。また、負極活物質、結着材および導電材を固体状態で混合し、得られた混合物をニッケルメッシュに圧着し、乾燥し、プレスすることにより作製することができる。なかでも、負極活物質、結着材および導電材をNMPなどの有機溶剤に懸濁させる方法は、均質な電極が作成できるために好ましい。
なお、本実施形態に係る第1実施形態として電極が負極である場合を例に説明したが、これに限定されるものではなく、電極が正極である場合についても適用できることはいうまでもない。このことは、以下に説明する実施形態についても同様である。
第2実施形態に係る非水電解質二次電池を説明する。
第2実施形態に係る非水電解質二次電池は、正極と、負極と、正極及び負極の間に形成された非水電解質層と、正極、負極と電解質を収容するケースとを具備する。
正極端子は、リチウムイオン金属に対する電位が3V以上4.25V以下の範囲における電気的安定性と導電性とを備える材料を用いることができる。具体的には、アルミニウムまたはMg、Ti、Zn、Mn、Fe、Cu、Si等の元素を含むアルミニウム合金が挙げられる。正極端子は、正極集電体との接触抵抗を低減するために、正極集電体と同様の材料であることが好ましい。
袋状外装材は、厚さ0.5mm以下のラミネートフィルムから形成される。或いは、外装材は厚さ1.0mm以下の金属製容器が用いられる。金属製容器は、厚さ0.5mm以下であることがより好ましい。
負極は、第1実施形態の正極を用いる。なお、正極が本実施形態に関わる正極である場合、負極活物質、および結着材としては、非水電解質二次電池として用いられる化合物であれば、特に限定されるものではない。
正極は、正極活物質、結着材および導電材を混合し、集電体表面に担持することにより作製される。例えば、正極活物質、結着材および導電材を適当な溶媒に懸濁させ、得られた懸濁物をAl合金箔に塗布し、乾燥し、プレスすることにより作製することができる。また、正極活物質、結着材および導電材を固体状態で混合し、得られた混合物をAl合金メッシュに圧着し、乾燥し、プレスすることにより作製することができる。なかでも、正極活物質、結着材および導電材をNMPなどの有機溶剤に懸濁させる方法は、均質な電極が作成できるために好ましい。実施形態の正極活物質は、Liの挿入脱離を行う。正極活物質としては、非水電解質二次電池として用いられる正極活物質であれば特に限定されるものでなく使用することができる。例えば、リチウムとリチウム以外の金属を含むリチウム複合酸化物やリチウム複合リン酸化合物、ポリアニリンやポリピロールのような導電性高分子、硫黄を含むジスルフィド系高分子、あるいはフッ化炭素などを挙げることができる。
Mnを含む複合酸化物としては、例えばLiMn2O4、Li(1+x)Mn(2-x-y)MyOz(0≦x≦0.2、0≦y≦1.1、3.9≦z≦4.1、MはNi、Co、Feから選ばれる少なくとも1種類以上の元素)を用いることができる。
Niを含む複合酸化物としては、例えばLi(NixMy)O2(x+y=1、0<x≦1、0≦y<1、MはCo、Alから選ばれる少なくとも1種類以上の元素)を挙げることができる。
VあるいはCrを含む複合酸化物としては、例えばLiVO2、LiCrO2等を挙げることができる。
リチウム複合リン酸化合物としては、LiCoPO4、LiMnPO4、LiFePO4あるいはLi(FexMy)PO4 (x+y=1、0<x<1、MはCo、Mnより選ばれる少なくとも1種類以上の元素)、Li(CoxMny)PO4 (x+y=1、0<x<1)で表される複合リン酸化合物を挙げることができる。
以上10質量%以下の範囲にすることが好ましい。
非水電解質は、非水溶媒に電解質を溶解することにより調製される。非水溶媒の例は、エステル、炭酸エステル、スルホン酸エステル化合物を用いることができる。具体的には、エチレンカーボネート、プロピレンカーボネート、エチルメチルカーボネート、ジエチルカーボネート、ジメチルカーボネート、γ-ブチロラクトン、γ-バレロラクトン、α-アセチル-γ-ブチロラクトン、α-メチル-γ-ブチロラクトン、メチルアセテート、エチルアセテート、メチルプロピオネート、エチルブチレート、ブチルアセテート、n-プロピルアセテート、イソブチルプロピオネート、ベンジルアセテート、メタンスルホン酸エチル、メタンスルホン酸プロピル、エタンスルホン酸メチル、エタンスルホン酸プロピル、プロパンスルホン酸メチル、プロパンスルホン酸エチルなどを挙げることができ、これらは単独で用いてもよく、2種以上を組み合わせて用いてもよい。これらのうちでは、エチレンカーボネート、プロピレンカーボネート、γ-ブチロラクトンより選ばれる少なくとも1種の非水溶媒と、エチルメチルカーボネート、ジエチルカーボネート、ジメチルカーボネートより選ばれる少なくとも1種の非水溶媒を混合して用いることが好ましい。
実施形態の非水溶媒としては、例えば以下の組成のいずれかが好ましい。
エチレンカーボネート5容量%以上50容量%以下およびエチルメチルカーボネート50容量%以上95容量%以下からなる合計100容量%の非水溶媒。
エチレンカーボネート5容量%以上50容量%以下およびジエチルカーボネート50容量%以上95容量%以下からなる合計100容量%の非水溶媒。
エチレンカーボネート5容量%以上40容量%以下、プロピレンカーボネート20容量%以上80容量%以下およびγ-ブチロラクトン5容量%以上40容量%以下からなる合計100容量%の非水溶媒。
前記非水電解質中には、ガスの発生を抑える効果をさらに向上させる観点から、炭酸エステル系添加剤および硫黄化合物系添加剤よりなる群から選ばれた少なくとも1種が添加されていることが好ましい。炭酸エステル系添加剤は、皮膜形成等により、負極表面で発生するH2、CH4などのガスを低減させる効果を有し、硫黄化合物系添加剤は、皮膜形成等により、正極表面で発生するCO2などのガスを低減させる効果を有すると考えられる。
炭酸エステル系添加剤および硫黄化合物系添加剤を併用する場合、これらの添加比率(炭酸エステル系添加剤:硫黄化合物系添加剤)は、1:9から9:1であることが、両者の効果をバランス良く得ることができる点で好ましい。
非水電解液を用いる場合、および電解質含浸型ポリマー電解質を用いる場合においてはセパレータを用いることができる。セパレータは多孔質セパレータを用いる。セパレータは、例えば、ポリテトラフルオロエチレン,ポリプロピレンあるいはポリエチレンなどの合成樹脂製の多孔質膜、またはセラミック製の多孔質膜により構成されており、これら2種以上の多孔質膜を積層した構造とされていてもよい。
セパレータは、多孔度が30%以上70%以下の範囲であることが好ましい。これは次のような理由によるものである。多孔度を30%未満にすると、セパレータにおいて高い電解質保持性を得ることが困難になる恐れがある。一方、多孔度が60%を超えると十分なセパレータ強度を得られなくなる恐れがある。多孔度のより好ましい範囲は、35%以上70%以下である。
空気透過率の上限値は300秒/1.00cm3にすることがより好ましく、また、下限値は50秒/1.00cm3にするとより好ましい。
次に、第3実施形態に係る電池パックを説明する。
第3実施形態に係る電池パックは、上記第2実施形態に係る非水電解質二次電池(即ち、単電池)を一以上有する。電池パックに複数の単電池が含まれる場合、各単電池は、電気的に直列、並列、或いは、直列と並列に接続して配置される。
図7の概念図及び図8のブロック図を参照して電池パック300を具体的に説明する。図7に示す電池パック300では、単電池301として図5に示す扁平型非水電解液電池200を使用している。
配線316a及びマイナス側配線316bを遮断できる。所定の条件とは、例えばサーミスタ307の検出温度が所定温度以上になったときである。また、所定の条件とは単電池301の過充電、過放電、過電流等を検出したときである。この過充電等の検出は、個々の単電池301もしくは単電池301全体について行われる。個々の単電池301を検出する場合、電池電圧を検出してもよいし、正極電位もしくは負極電位を検出してもよい。後者の場合、個々の単電池301中に参照極として用いるリチウム電極が挿入される。図5及び図6の場合、単電池301それぞれに電圧検出のための配線317を接続し、これら配線317を通して検出信号が保護回路308に送信される。
以上記載した本実施形態によれば、上記第3実施形態における優れた充放電サイクル性能を有する非水電解質二次電池を備えることにより、優れた充放電サイクル性能を有する電池パックを提供することができる。
結着材としてPVdFを用いた。熱重量分析装置により測定した結果、熱分解温度T1は450℃、熱分解終了温度T2は500℃であった。475℃における熱分解ガスクロマトグラフ質量分析では、質量数132と200のフラグメントが存在した。
活物質にLi4Ti5O12、結着材にPVdF、導電材にアセチレンブラックを用い、組成比を重量比で80:5:15として負極を作成した。まず、PVdFを10重量%となるようにNMPに溶解し、負極活物質と共にボールミルに投入、4時間攪拌して負極活物質ペーストを作成した。作成したペーストは、ボールミルから取り出してボールを除き、アセチレンブラックと共に2枚の攪拌羽を具備する攪拌容器に投入、室温で30分間攪拌して負極スラリーを作成した。作成した負極スラリーは、アプリケータを用いて銅箔上に塗布、大気圧下130℃で乾燥した後、さらに150℃で真空乾燥して負極を作成した。
作成した負極の活物質層を削りとり、熱分解質ガスクロマトグラフ質量分析装置により分析した結果、熱分解温度475℃において132および200の質量数のイオンクロマトグラムにピークが存在し、かつ質量数132のピークが最も大きい面積を与えた。当該ピークの、熱分解温度450℃におけるピーク面積をX、熱分解温度500℃におけるピーク面積をYとしたとき、XとYは、2X≧Yの関係にあった。
得られた負極と、LiFePO4からなる正極と、非水電解液を用い、非水電解質二次電池を作成、60℃で充放電サイクル試験を実施した結果、2,000サイクル後の容量維持率は98%であった。
(実施例2)
活物質にシリコン粉末を用い、導電材に黒鉛を用い、活物質と結着材と導電材の組成比を重量比で75:20:5としたこと以外は実施例1と同様の手法により負極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X≧Yの関係であった。また、充放電サイクル試験において、50サイクル後の容量維持率は80%であった。
(実施例3)
活物質にシリコン/酸化シリコン/炭素複合材料を用いたこと以外は実施例2と同様の手法により負極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X≧Yの関係であった。また、充放電サイクル試験において、30サイクル後の容量維持率は80%であった。なお、シリコン/酸化シリコン/炭素複合材料は、一酸化シリコンと炭素前駆体を混合・焼成した後に粉砕することにより得た。
(実施例4)
活物質にシリコンナノチューブを用いたこと以外は実施例2と同様の手法により負極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X≧Yの関係であった。また、充放電サイクル試験において、100サイクル後の容量維持率は80%であった。
(実施例5)
活物質にLi(Ni5/10Co2/10Mn3/10)O2を用いたこと以外は実施例1と同様の手法により正極を作成した。得られた正極と、グラファイトからなる負極と、非水電解液を用い、非水電解質二次電池を作成、実施例1と同様の手法により充放電サイクル試験を実施した。XとYは、2X≧Yの関係であった。300サイクル後の容量維持率は90%であった。
(実施例6)
活物質にLiMn1.5Ni0.5O4を用いたこと以外は実施例5と同様の手法により正極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X≧Yの関係であった。200サイクル後の容量維持率は80%であった。
(実施例7)
正極活物質にLi(Fe0.4Mn0.6)PO4を用いたこと以外は実施例5と同様の手法により正極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X≧Yの関係であった。200サイクル後の容量維持率は85%であった。
活物質にLi4Ti5O12、結着材にPVdF、導電材にアセチレンブラックを用い、組成比を重量比で80:5:15として負極を作成した。まず、PVdFを10重量%となるようにNMPに溶解し、導電材と共にボールミルに投入、4時間攪拌して負極活物質ペーストを作成した。作成したペーストは、ボールミルから取り出してボールを除き、活物質と共に2枚の攪拌羽を具備する攪拌容器に投入、室温で30分間攪拌して負極スラリーを作成した。作成した負極スラリーは、アプリケータを用いて銅箔上に塗布、大気圧下130℃で乾燥した後、さらに150℃で真空乾燥して負極を作成した。
作成した負極の活物質層を削りとり、熱分解質ガスクロマトグラフ質量分析装置により分析した結果、熱分解温度475℃において132および200の質量数のイオンクロマトグラムにピークが存在し、かつ質量数132のピークが最も大きい面積を与えた。当該ピークの、熱分解温度450℃におけるピーク面積をX、熱分解温度500℃におけるピーク面積をYとしたとき、XとYは、2X<Yの関係にあった。
得られた負極と、LiFePO4からなる正極と、非水電解液を用い、非水電解質二次電池を作成、60℃で充放電サイクル試験を実施した結果、2,000サイクル後の容量維持率は90%であった。
活物質にシリコン粉末を用い、導電材に黒鉛を用い、活物質と結着材と導電材の組成比を重量比で75:20:5としたこと以外は比較例1と同様の手法により負極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X<Yの関係であった。また、充放電サイクル試験において、50サイクル後の容量維持率は65%であった。
活物質にシリコン/酸化シリコン/炭素複合材料を用いたこと以外は比較例2と同様の手法により負極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X<Yの関係であった。また、充放電サイクル試験において、30サイクル後の容量維持率は75%であった。なお、シリコン/酸化シリコン/炭素複合材料は、一酸化シリコンと炭素前駆体を混合・焼成した後に粉砕することにより得た。
活物質にシリコンナノチューブを用いたこと以外は比較例2と同様の手法により負極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X<Yの関係であった。また、充放電サイクル試験において、100サイクル後の容量維持率は60%であった。
活物質にLi(Ni5/10Co2/10Mn3/10)O2を用いたこと以外は比較例1と同様の手法により正極を作成した。得られた正極と、グラファイトからなる負極と、非水電解液を用い、非水電解質二次電池を作成、実施例1と同様の手法により充放電サイクル試験を実施した。XとYは、2X<Yの関係であった。300サイクル後の容量維持率は70%であった。
活物質にLiMn1.5Ni0.5O4を用いたこと以外は比較例5と同様の手法により正極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X<Yの関係であった。200サイクル後の容量維持率は60%であった。
正極活物質にLi(Fe0.4Mn0.6)PO4を用いたこと以外は比較例5と同様の手法により正極、および非水電解質二次電池を作成し、充放電サイクル試験を実施した。XとYは、2X<Yの関係であった。200サイクル後の容量維持率は75%であった。
以上のように、本発明によりに容量維持率に優れた非水電解質二次電池を作成することができた。
Claims (9)
- 活物質とフッ素を含有する結着材とを含む活物質層と前記活物質層と結着した集電体を有した電極であって、
前記結着材の熱分解開始温度がT1℃であり、熱分解終了温度がT2℃であるとき、
前記熱分解温度(T1+T2)/2℃における熱分解ガスクロマトグラフ質量分析において、少なくとも81、100、132、200より選ばれるいずれかの質量数のイオンクロマトグラムにピークが存在し、
前記T1℃におけるピーク面積をXとし、
前記T2℃におけるピーク面積をYとし、
前記XとYは、2X≧Yの条件を満たす非水電解質二次電池用電極。
ここで、前記結着材の熱分解開始温度は、結着材を熱重量分析法
にて分析した際、主となる重量減少過程において、前記重量減少過程における重量減少分の5%が減少する温度であり、
前記結着材の熱分解終了温度とは、結着材を熱重量分析装置にて分析した際、主となる重量減少過程において、前記重量減少過程における重量減少分の95%が減少する温度であり、
前記ピーク面積とは、前記結着材単体の熱分解温度(T1+T2)/2℃における熱分解ガスクロマトグラフ質量分析において、質量数81、100、132、200で抽出したイオンクロマトグラフのうち、最大の面積を与える質量数のピーク面積である。 - 前記結着材は、少なくともビニリデンジフルオライド、テトラフルオロエチレン、ポリクロロトリフルオロエチレン、フッ化ビニル、エチレン、テトラフルオロエチレンコポリマー、ヘキサフルオロプロペン、ポリフッ化ビニリデン-ヘキサフルオロプロペンコポリマー、ポリテトラフルオロエチレン-ヘキサフルオロプロペンコポリマーより選ばれる1種以上の化合物の原料を含有する請求項1記載の非水電解質二次電池用電極。
- 前記結着材は、ポリテトラフルオロエチレン(PTFE)、ポリフッ化ビニリデン(PVdF)、ポリテトラフルオロエチレンーフッ化ビニリデン(PTFE-PVdF)、ポリテトラフルオロエチレンーヘキサフルオロプロピレン(PTFE-HFP)より選ばれる高分子材料である請求項1又は2記載の非水電解質二次電池用電極。
- 電極活物質層に、導電材をさらに含む請求項1乃至3のいずれか1項に記載の非水電解質二次電池用電極。
- 前記活物質は、少なくともシリコン、スズ、アンチモン、アルミニウム、マグネシウム、ビスマス、チタンより選ばれる1種以上の元素を金属、合金、酸化物、リン化物、セラミクス、硫化物、リチウム複合酸化物より選ばれる形態により含有する請求項1乃至4のいずれか1項に記載の非水電解質二次電池用電極。
- 請求項1乃至5のいずれか1項に記載の電極を用いた負極と、
正極と、
前記正極及び負極の間に形成された非水電解質層と、
前記正極、負極と電解質を収容するケースとを具備した非水電解質二次電池。 - 前記活物質は、少なくとも充電終止電圧がリチウム電位基準に対して4.0V以上である、リチウム複合酸化物、リチウム複合リン酸化合物より選ばれる1種以上の化合物を含有する請求項1乃至4のいずれか1項に記載の非水電解質二次電池用電極。
- 請求項1乃至4又は7のいずれか1項に記載の電極を用いた正極と、
負極と、
前記正極及び負極の間に形成された非水電解質層と、
前記正極、負極と電解質を収容するケースとを具備した非水電解質二次電池 - 前記請求項6又は8に記載の非水電解質二次電池を用いた電池パック
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