WO2013021630A1 - Negative electrode for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery - Google Patents

Negative electrode for nonaqueous electrolyte secondary batteries, and nonaqueous electrolyte secondary battery Download PDF

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Publication number
WO2013021630A1
WO2013021630A1 PCT/JP2012/005022 JP2012005022W WO2013021630A1 WO 2013021630 A1 WO2013021630 A1 WO 2013021630A1 JP 2012005022 W JP2012005022 W JP 2012005022W WO 2013021630 A1 WO2013021630 A1 WO 2013021630A1
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layer
negative electrode
electrolyte secondary
secondary battery
battery
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PCT/JP2012/005022
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French (fr)
Japanese (ja)
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一樹 遠藤
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パナソニック株式会社
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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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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

  • the present invention relates to a negative electrode for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery, and more particularly to a negative electrode for a nonaqueous electrolyte secondary battery with improved safety.
  • the non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator disposed so as to be interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.
  • a positive electrode, a negative electrode, and a separator are wound to form an electrode group.
  • a negative electrode for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as a negative electrode) has a current collector and a negative electrode mixture layer attached to the surface of the current collector.
  • the negative electrode mixture layer includes a negative electrode active material, a binder, and a conductive material as necessary.
  • a separator having a shutdown function is used.
  • the pores of the separator are blocked and the ionic current is interrupted. Thereby, a short circuit current stops flowing and further heat generation is suppressed.
  • the separator may melt and the shutdown function may not be exhibited (meltdown).
  • the positive electrode and the negative electrode are short-circuited due to meltdown, further overheating is caused.
  • Patent Document 1 proposes a technique for forming a porous film made of an inorganic oxide filler such as alumina and a water-soluble polymer on the surface of the active material layer. Thereby, it is said that the insulation between positive and negative electrodes can be maintained even in an overheated environment.
  • Patent Document 2 proposes a technique for forming a surface layer made of a lithium titanium composite oxide capable of inserting and extracting lithium on the surface of a main layer containing an active material. It is stated that the surface layer has a function of suppressing a current from flowing between the positive and negative electrodes through foreign matter.
  • a main layer is arranged on the surface of the current collector, and a surface layer that functions as an insulating layer at the time of a short circuit is arranged on the surface of the main layer.
  • the thickness of the main layer attached to the current collector is generally increased from the viewpoint of ensuring energy density. However, if the thickness of the main layer is increased, the adhesion between the current collector and the main layer tends to be insufficient.
  • the main layer to which the surface layer is attached may be peeled off from the current collector. As a result, it is considered that the current layer is exposed without the surface layer functioning as an insulating layer, and the effect of suppressing the short circuit between the positive and negative electrodes is not sufficiently exhibited.
  • the present invention provides a negative electrode for a non-aqueous electrolyte secondary battery that can suppress an excessive increase in battery temperature and has excellent safety even when an internal short circuit occurs due to a foreign substance such as a nail and a large stress is applied to the negative electrode.
  • the purpose is to provide.
  • One aspect of the present invention includes a current collector, a first layer attached to a surface of the current collector, and a second layer attached to a surface of the first layer, wherein the first layer includes inorganic oxide particles and Including a first binder, and the second layer includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder, the thickness T 1 of the first layer, and the second layer
  • the layer thickness T 2 relates to a negative electrode for a non-aqueous electrolyte secondary battery in which T 1 ⁇ T 2 is satisfied.
  • Another aspect of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the negative electrode is the negative electrode for a non-aqueous electrolyte secondary battery described above. Next battery.
  • FIG. 1 is a longitudinal sectional view schematically showing a configuration of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.
  • the negative electrode for a non-aqueous electrolyte secondary battery has a current collector and a negative electrode mixture layer attached to the surface of the current collector.
  • a large stress is applied to the negative electrode, for example, when the negative electrode is broken by a relatively large foreign object such as a nail, in the conventional negative electrode, the negative electrode mixture layer may be peeled off to expose the current collector.
  • the negative electrode mixture layer may be peeled off to expose the current collector.
  • it becomes difficult to maintain insulation between the positive electrode and the negative electrode leading to an expansion of internal short circuit and an excessive increase in battery temperature.
  • the present inventors by arranging a high resistance layer with a small thickness on the surface of the current collector, the high resistance layer is peeled off from the current collector even when a large stress is applied to the negative electrode. It was difficult to obtain excellent safety.
  • a negative electrode for a non-aqueous electrolyte secondary battery includes a current collector, a first layer containing inorganic oxide particles and a first binder, a carbon material capable of reversibly occluding and releasing lithium ions, and And a second layer containing a second binder.
  • the first layer functions as a high resistance layer
  • the second layer functions as a negative electrode mixture layer responsible for battery reaction.
  • the first layer functions not only as a high resistance layer but also as a negative electrode mixture layer responsible for battery reaction. You can also.
  • the first layer does not have a role to play an electrode reaction or has a small role, so that it is not necessary to consider the acceptability of lithium ions. Accordingly, the first layer can contain a relatively large amount of the first binder. The first layer is formed relatively thin. Therefore, even if a large stress is applied to the negative electrode, the first layer is difficult to peel off from the current collector. Therefore, expansion of the internal short circuit and excessive increase in battery temperature can be suppressed, and the safety of the nonaqueous electrolyte secondary battery is improved.
  • FIG. 1 is a longitudinal sectional view schematically showing a configuration of a negative electrode for a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.
  • the negative electrode 10 includes a first layer 12 attached to the surface of the current collector 11 and a second layer 13 attached to the surface of the first layer 12.
  • the first layer includes inorganic oxide particles and a first binder
  • the second layer 13 includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder.
  • the thickness T 1 of the first layer 12, the thickness T 2 of the second layer 13 satisfies T 1 ⁇ T 2.
  • Ratio of T 1 and T 2 By making T 1 / T 2 smaller than 1 , the influence on the discharge characteristics of T 1 which is a high resistance layer can be suppressed, and the energy density of the entire negative electrode is sufficiently increased It can also be secured.
  • T 1 / T 2 is preferably 0.15 or more and 0.8 or less, and more preferably 0.55 or less. By setting T 1 / T 2 to 0.15 or more, it becomes easy to prevent an excessive increase in battery temperature during an abnormality. On the other hand, by setting T 1 / T 2 to 0.8 or less, preferably 0.55 or less, the energy density of the entire negative electrode is sufficiently ensured while sufficiently securing the adhesion between the current collector and the first layer. Can be secured.
  • the thickness T 1 of the first layer 12 is preferably 1 to 40 ⁇ m, and more preferably 1 to 30 ⁇ m. By setting T 1 to 1 ⁇ m or more, the first layer can sufficiently exhibit the function as the high resistance layer at the time of a short circuit. On the other hand, when T 1 is set to 40 ⁇ m or less, adhesion to the current collector and energy density can be sufficiently ensured.
  • the thickness T 2 of the second layer 13 is preferably 50 to 100 ⁇ m. By setting T 2 to 50 ⁇ m or more, a higher energy density can be secured. On the other hand, by setting T 2 to 100 ⁇ m or less, better lithium ion acceptability can be obtained.
  • Density of the first layer is preferably 1 ⁇ 5 g / cm 3, more preferably 1.5 ⁇ 4g / cm 3.
  • Density of the second layer is preferably 1.2 ⁇ 1.7g / cm 3, more preferably 1.3 ⁇ 1.6g / cm 3.
  • inorganic oxide particles insulating inorganic oxide particles that do not occlude and release lithium ions, such as alumina, silica, and magnesia, may be used, and the lithium ions having a layered or spinel crystal structure are reversible.
  • inorganic oxide particles that can be occluded and released may be used.
  • the first layer containing inorganic oxide particles capable of reversibly occluding and releasing lithium ions normally functions as a negative electrode mixture layer responsible for battery reaction, and releases lithium ions when an internal short circuit of the battery occurs. Function as a high resistance layer. Thereby, expansion of an internal short circuit and the excessive raise of battery temperature can be suppressed, maintaining a high energy density.
  • the inorganic oxide particles capable of reversibly occluding and releasing lithium ions include lithium titanate having a spinel crystal structure because it has electronic conductivity when occluding lithium ions.
  • Lithium titanate has high acceptability of lithium ions and can easily reduce the diffusion resistance of the negative electrode.
  • the first layer containing such inorganic oxide particles is liable to occlude lithium in a region where the negative electrode potential is higher than that of metallic lithium (that is, in the initial stage of charging). Therefore, even if the amount of the first binder is relatively large, it is easy to maintain sufficient lithium ion acceptability. That is, the adhesion between the current collector and the first layer and the lithium ion acceptability of the entire negative electrode can be achieved at a high level.
  • lithium titanate does not have conductivity in a state where lithium ions are not occluded, and has higher thermal stability than a carbon material. Therefore, in the unlikely event that an internal short circuit of the battery occurs, insulation between the positive and negative electrodes can be maintained, and heat generation is also suppressed. Therefore, expansion of the internal short circuit and excessive increase of the battery temperature can be more reliably suppressed.
  • a typical lithium titanate is represented by the general formula: Li 4 Ti 5 O 12 .
  • Li x Ti 5-y M y O 12 + z (where element M is vanadium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, boron, magnesium, calcium, strontium, barium, zirconium , Niobium, molybdenum, tungsten, bismuth, sodium, gallium and rare earth elements, and x, y and z are 3 ⁇ x ⁇ 5, 0 ⁇ y ⁇ 1.5, respectively.
  • 0.005 ⁇ y ⁇ 1.5 and ⁇ 1 ⁇ z ⁇ 1 are satisfied, and x is a value immediately after synthesis or in a fully discharged state).
  • the average particle diameter of the inorganic oxide particles (median diameter in the volume-based particle size distribution: D 50 ) is preferably 0.1 to 5 ⁇ m.
  • the average particle size is included in the above range, for example, lithium titanate has particularly high lithium ion acceptability.
  • the volume-based particle size distribution of the inorganic oxide particles can be measured by, for example, a commercially available laser diffraction particle size distribution measuring device.
  • the BET specific surface area of the inorganic oxide particles is preferably 0.5 to 20 m 2 / g.
  • lithium titanate has particularly high lithium ion acceptability.
  • Examples of the first binder include a fluororesin, a polyolefin resin, an acrylic resin, and a particulate binder having rubber elasticity.
  • Examples of the fluororesin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene, and the like.
  • Examples of the polyolefin resin include polyethylene and polypropylene.
  • Acrylic resins include polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid.
  • examples include hexyl esters.
  • examples of the particulate binder having rubber elasticity include styrene butadiene rubber.
  • other first binders include aramid resin, polyamide, polyimide, polyamideimide, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyethersulfone, carboxymethylcellulose, and the like.
  • a 1st binder may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the amount W 1 of the first binder is not particularly limited as long as sufficient adhesion between the current collector 11 and the first layer 12 can be secured.
  • the amount W 1 is 0 per 100 parts by mass of the inorganic oxide particles.
  • the amount is preferably 5 to 10 parts by mass, particularly preferably 3 to 7 parts by mass. Thereby, sufficient adhesion between the current collector and the first layer can be ensured. Further, when inorganic oxide particles capable of reversibly occluding and releasing lithium ions are used, both the adhesion to the current collector and the lithium ion acceptability can be achieved at a high level.
  • the amount W 1 of the first binder contained in the first layer is preferably larger than the amount W 2 of the second binder contained in the second layer, and the ratio of W 1 and W 2 : W 1 / More preferably, W 2 satisfies 3 to 10.
  • the first layer 12 may further contain a conductive material.
  • a conductive material include, for example, graphite particles such as various natural graphites and various artificial graphites, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black or thermal black, carbon fiber, metal Examples thereof include conductive fibers such as fibers and carbon fluoride.
  • the amount of the conductive material in the first layer is not particularly limited, for example, from the viewpoint of functioning the first layer as a high resistance layer in the case of an internal short circuit while ensuring electrical continuity between the current collector and the second layer 13, for example,
  • the amount is preferably 1 to 5 parts by mass per 100 parts by mass of the inorganic oxide particles.
  • the second layer 13 includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder.
  • carbon materials capable of reversibly occluding and releasing lithium ions include graphite particles such as various natural graphites and various artificial graphites, coke, hard carbon, soft carbon, graphitized carbon, carbon fiber, spherical carbon, and amorphous. Carbon. Among these, graphite particles are preferably used from the viewpoint of easily obtaining a high-capacity negative electrode.
  • the average particle diameter (median diameter in volumetric particle size distribution: D 50 ) of the carbon material is preferably 5 to 30 ⁇ m.
  • D 50 average particle diameter
  • graphite particles are advantageous in that the sliding property of the particles in the second layer is improved and the filling state is easily improved.
  • the volume-based particle size distribution of the carbon material can be measured by, for example, a commercially available laser diffraction particle size distribution measuring apparatus.
  • the carbon material preferably has a BET specific surface area of 2 to 6 m 2 / g.
  • BET specific surface area is included in the above range, for example, graphite particles are advantageous in that the sliding property of the particles in the second layer is improved and the filling state is easily improved.
  • the second layer 13 is composed of a simple substance such as silicon (Si) or tin (Sn), an alloy containing these elements, or a silicon compound (for example, SiO x (0 ⁇ x ⁇ 2)). Or a solid solution containing silicon, a tin compound (eg, a solid solution containing tin), or the like.
  • the second binder for example, one or more kinds of those exemplified as the first binder can be arbitrarily selected and used.
  • the amount of the second binder is preferably 0.4 to 1.5 parts by mass per 100 parts by mass of the carbon material, for example.
  • the material of the current collector 11 is not particularly limited, but copper foil, copper alloy foil, nickel foil and the like are preferable.
  • the thickness of the current collector is, for example, 5 to 30 ⁇ m, but is not particularly limited.
  • the method for producing the negative electrode for the nonaqueous electrolyte secondary battery is not particularly limited.
  • a first layer slurry containing inorganic oxide particles, a first binder, and a dispersion medium, and a second layer slurry containing a carbon material, a second binder, and a dispersion medium are prepared.
  • the first layer slurry is applied to the surface of the current collector, dried, and rolled to an arbitrary thickness to form the first layer.
  • the negative electrode is obtained by apply
  • a die coater or the like having two or more discharge slits the first layer slurry and the second layer slurry may be simultaneously applied and dried.
  • the non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.
  • the positive electrode includes a current collector and a positive electrode mixture layer attached to the surface of the current collector.
  • the positive electrode mixture layer includes a positive electrode active material as an essential component, and includes a binder, a conductive material, and the like as optional components.
  • a lithium composite metal oxide can be used as the positive electrode active material. Examples of the lithium composite metal oxide include Li x CoO 2 , Li x NiO 2 , Li x MnO 2 , Li x Co y Ni 1 -y O 2 , Li x Co y M 1 -y O z , and Li x Ni.
  • x value which shows the molar ratio of lithium is a value immediately after active material preparation, and increases / decreases by charging / discharging.
  • the lithium composite metal oxide may have a metal element partially substituted with a different element. Further, the lithium composite metal oxide may be surface-treated with a metal oxide, lithium oxide, a conductive agent, or the like, and the surface may be subjected to a hydrophobic treatment.
  • the non-aqueous electrolyte includes a non-aqueous solvent and a solute that dissolves therein.
  • Nonaqueous solvents include, for example, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). It is not limited to.
  • a non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the solute include lithium salts such as LiBF 4 , LiPF 6 , LiAlCl 4 , LiCl, and lithium imide salt. Only one solute may be used alone, or two or more solutes may be used in combination.
  • Example 1 Production of negative electrode (first layer) 2 kg of lithium titanate having a spinel crystal structure (Li 4 Ti 5 O 12 , average particle size 1 ⁇ m, BET specific surface area 3 m 2 / g), artificial graphite (average particle size 10 ⁇ m) 50 g, Nippon Zeon Co., Ltd. 100 g of BM-400B (modified styrene-butadiene rubber dispersion having a solid content of 40% by mass), 50 g of carboxymethylcellulose (CMC), and an appropriate amount of water as a dispersion medium were mixed in a double-arm kneader. The mixture was stirred to prepare a first layer slurry containing lithium titanate.
  • BM-400B modified styrene-butadiene rubber dispersion having a solid content of 40% by mass
  • CMC carboxymethylcellulose
  • the obtained first layer slurry is applied to both sides of a negative electrode current collector made of a copper foil having a thickness of 10 ⁇ m, dried, and rolled to a total thickness of 30 ⁇ m to form a first layer. did. That is, the thickness (T 1 ) of the first layer was 10 ⁇ m per one side of the copper foil. The density of the first layer was 2 g / cm 3 .
  • the obtained slurry for the second layer was applied to the surface of the first layer adhered to both surfaces of the copper foil, dried, and rolled to a total thickness of 160 ⁇ m to form a second layer.
  • the thickness (T 2 ) of the second layer was 65 ⁇ m per side.
  • the density of the second layer was 1.5 g / cm 3 .
  • the obtained electrode plate was cut into a width of 58 mm and a length of 750 mm to obtain a negative electrode having T 1 / T 2 of 0.15.
  • the positive electrode 25 and the negative electrode 26 produced in the above (i) and (ii) are wound together with a separator 27 (20 ⁇ m-thick polyethylene microporous film) interposed between them to form a cylindrical electrode group Configured.
  • An electrode group was housed inside a nickel-plated bottomed cylindrical battery case 21 (diameter 18 mm, height 65 mm, inner diameter 17.85 mm).
  • An upper insulating plate 28a and a lower insulating plate 28b are disposed at both ends in the longitudinal direction of the electrode group.
  • One end of an aluminum positive electrode lead 25 a was connected to the positive electrode 25, and the other end was connected to the lower surface of the sealing plate 22.
  • a nickel negative electrode lead 26 a was connected to the negative electrode 26, and the other end was connected to the inner bottom surface of the battery case 21. Thereafter, 5.5 g of a non-aqueous electrolyte was injected into the battery case 21, and the electrode group was impregnated with the non-aqueous electrolyte. Next, the sealing plate 22 was disposed in the opening of the battery case 21, and the opening end of the battery case 21 was caulked to the peripheral portion of the sealing plate 22 via the gasket 23. In this manner, a cylindrical nonaqueous electrolyte secondary battery (battery A) having a design capacity of 2150 mAh was produced.
  • Example 2 A negative electrode was produced in the same manner as in Example 1 except that T 1 and T 2 were 1 ⁇ m and 70 ⁇ m, respectively, and a battery B was produced.
  • Example 3 A negative electrode was produced in the same manner as in Example 1 except that T 1 and T 2 were 5 ⁇ m and 70 ⁇ m, respectively, and a battery C was produced.
  • Example 4 T 1 and T 2 was a 30 ⁇ m and 55 ⁇ m respectively, negative very long of 710 mm, except that the Seikyokucho of 660 mm, in the same manner as in Example 1, to prepare a battery D.
  • Example 5 Battery E was produced in the same manner as in Example 1, except that T 1 and T 2 were 40 ⁇ m and 50 ⁇ m, respectively, the negative electrode length was 700 mm, and the positive electrode length was 650 mm.
  • Example 6 A battery F was produced in the same manner as in Example 1, except that T 1 and T 2 were 45 ⁇ m and 50 ⁇ m, respectively, the negative electrode length was 695 mm, and the positive electrode length was 645 mm.
  • Example 7 A negative electrode was produced in the same manner as in Example 2 except that alumina (Al 2 O 3 , average particle size 0.3 ⁇ m) was used as the first layer of inorganic oxide particles instead of lithium titanate, and battery G was made.
  • alumina Al 2 O 3 , average particle size 0.3 ⁇ m
  • Comparative Example 1 A battery H was fabricated in the same manner as in Example 1, except that T 1 and T 2 were 50 ⁇ m and 40 ⁇ m, respectively, the negative electrode length was 680 mm, and the positive electrode length was 630 mm.
  • Comparative Example 2 A battery I was produced in the same manner as in Example 2 except that the first layer was not formed and the second layer was adhered to the surface of the copper foil.
  • the batteries A to I were subjected to the following nail penetration test and charge / discharge test to evaluate the safety of each battery and the battery characteristics of each battery.
  • Constant current charging Current value 1C, end-of-charge voltage 4.2V Constant voltage charging: Voltage value 4.2V, charging end current 100mA Constant current discharge: current value 1C, final discharge voltage 1.0V
  • Batteries A to G had a low battery surface temperature during nail penetration and exhibited a high capacity retention rate.
  • the batteries A and D to F had particularly low battery surface temperatures during nail penetration.
  • the first layer has a sufficient thickness, it is considered that the first layer functioned well as a high resistance layer at the time of short circuit.
  • the batteries A to D showed a particularly high capacity retention rate.
  • the thickness T 1 is 40 ⁇ m of the first layer is believed that the capacity retention ratio was slightly reduced.
  • Cell F is considered as the thickness T 1 of the first layer is thicker and 45 [mu] m, the capacity retention ratio was lower than the battery E.
  • battery G used alumina, which is an insulating oxide that does not occlude and release lithium ions, as an inorganic oxide particle, it is considered that the capacity retention rate was slightly lowered.
  • Battery H which is a comparative example, had a significant decrease in capacity maintenance rate and a small battery capacity.
  • Battery H Since the thickness T 1 of the first layer is larger than the thickness T 2 of the second layer, the first layer becomes excessive resistance, charge and discharge characteristics and the energy density is believed to have decreased. Since the battery I does not have the first layer, an internal short circuit at the time of nail penetration and an excessive increase in the battery temperature could not be suppressed.
  • the non-aqueous electrolyte secondary battery according to the present invention is useful as a technology that can be developed not only for small power sources such as portable electronic devices but also for large power sources such as EVs (Electric Vehicles).

Abstract

The present invention relates to a negative electrode for nonaqueous electrolyte secondary batteries, which is provided with a collector, a first layer that adheres to the surface of the collector and a second layer that adheres to the surface of the first layer. The first layer contains inorganic oxide particles and a first binder; the second layer contains a second binder and a carbon material that is capable of reversibly absorbing and desorbing lithium ions; and the thickness (T1) of the first layer and the thickness (T2) of the second layer satisfy T1 < T2. Since the present invention is able to suppress excessive temperature increase of a battery even in cases where an internal short circuit has occurred and a large stress is applied to the negative electrode, an excellently safe nonaqueous electrolyte secondary battery can be obtained.

Description

非水電解質二次電池用負極および非水電解質二次電池Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery
　本発明は、非水電解質二次電池用負極および非水電解質二次電池に関し、詳しくは、安全性が改良された非水電解質二次電池用負極に関する。 The present invention relates to a negative electrode for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery, and more particularly to a negative electrode for a nonaqueous electrolyte secondary battery with improved safety.
　近年、携帯電話やノートパソコンなどの電子機器の電源および車載用電源として、二次電池に対する高エネルギー密度化が要求されている。このような要求から、高エネルギー密度化が可能な非水電解質二次電池が広く普及している。非水電解質二次電池は、正極、負極、正極と負極との間に介在するように配されるセパレータおよび非水電解質を備える。例えば、円筒型の非水電解質二次電池では、正極、負極およびセパレータが、捲回されて電極群を構成している。非水電解質二次電池用負極（以下、単に負極ともいう）は、集電体と、集電体の表面に付着した負極合剤層とを有する。負極合剤層は、負極活物質と、結着剤と、必要に応じて導電材とを含む。 In recent years, there has been a demand for higher energy density for secondary batteries as power sources for electronic devices such as mobile phones and laptop computers and power sources for vehicles. Due to such demands, non-aqueous electrolyte secondary batteries capable of increasing energy density are widely used. The non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator disposed so as to be interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. For example, in a cylindrical nonaqueous electrolyte secondary battery, a positive electrode, a negative electrode, and a separator are wound to form an electrode group. A negative electrode for a non-aqueous electrolyte secondary battery (hereinafter also simply referred to as a negative electrode) has a current collector and a negative electrode mixture layer attached to the surface of the current collector. The negative electrode mixture layer includes a negative electrode active material, a binder, and a conductive material as necessary.
　電池の内部で比較的抵抗値が低い短絡が発生した場合、短絡点に大電流が集中して流れる。そのため、電池の発熱が拡大して過熱に至ることがある。このような過熱を防止する観点から、エネルギー密度の高い非水電解質二次電池には、様々な安全対策がなされている。 When a short circuit with a relatively low resistance value occurs inside the battery, a large current flows at the short circuit point. For this reason, the heat generation of the battery may expand and lead to overheating. From the viewpoint of preventing such overheating, various safety measures have been taken for non-aqueous electrolyte secondary batteries with high energy density.
　例えば、シャットダウン機能を有するセパレータが用いられている。内部短絡によって電池が発熱すると、セパレータの細孔が閉塞してイオン電流が遮断される。これにより、短絡電流が流れなくなり、更なる発熱が抑制される。しかし、短絡部の発熱が大きい場合、セパレータが溶融してシャットダウン機能が発現しない場合がある（メルトダウン）。メルトダウンにより正極と負極とが短絡すると、更なる過熱を引き起こす。 For example, a separator having a shutdown function is used. When the battery generates heat due to an internal short circuit, the pores of the separator are blocked and the ionic current is interrupted. Thereby, a short circuit current stops flowing and further heat generation is suppressed. However, when the heat generation in the short-circuit portion is large, the separator may melt and the shutdown function may not be exhibited (meltdown). When the positive electrode and the negative electrode are short-circuited due to meltdown, further overheating is caused.
　そこで、特許文献１は、アルミナなどの無機酸化物フィラーと水溶性高分子とからなる多孔膜を、活物質層の表面に形成する技術を提案している。これにより、過熱環境下でも正負極間の絶縁を保つことができるとされている。 Therefore, Patent Document 1 proposes a technique for forming a porous film made of an inorganic oxide filler such as alumina and a water-soluble polymer on the surface of the active material layer. Thereby, it is said that the insulation between positive and negative electrodes can be maintained even in an overheated environment.
　特許文献２は、活物質を含む主要層の表面に、リチウムを吸蔵および放出可能なリチウムチタン複合酸化物からなる表面層を形成する技術を提案している。表面層は、正負極間に異物を通して電流が流れるのを抑制する機能を有すると述べられている。 Patent Document 2 proposes a technique for forming a surface layer made of a lithium titanium composite oxide capable of inserting and extracting lithium on the surface of a main layer containing an active material. It is stated that the surface layer has a function of suppressing a current from flowing between the positive and negative electrodes through foreign matter.
特開平９－１４７９１６号公報JP-A-9-147916 特開２０１０－９７７２０号公報JP 2010-97720 A
　特許文献１および２では、集電体の表面に主要層を配置し、主要層の表面に短絡時に絶縁層として機能する表面層を配置している。集電体と付着している主要層は、エネルギー密度を確保する観点から、厚さを大きくすることが一般的である。しかし、主要層の厚さを大きくすると、集電体と主要層との密着性が不十分になりやすい。 In Patent Documents 1 and 2, a main layer is arranged on the surface of the current collector, and a surface layer that functions as an insulating layer at the time of a short circuit is arranged on the surface of the main layer. The thickness of the main layer attached to the current collector is generally increased from the viewpoint of ensuring energy density. However, if the thickness of the main layer is increased, the adhesion between the current collector and the main layer tends to be insufficient.
　例えば、釘などの大きな異物による電極の破壊を伴う内部短絡では、負極に大きな応力が印加される。そのため、表面層が付着している主要層が、集電体から剥がれるおそれがある。その結果、表面層が絶縁層として機能せずに集電体が露出し、正負極間の短絡を抑制する効果が十分に発揮されないと考えられる。 For example, in the case of an internal short circuit accompanied by the destruction of the electrode by a large foreign object such as a nail, a large stress is applied to the negative electrode. Therefore, the main layer to which the surface layer is attached may be peeled off from the current collector. As a result, it is considered that the current layer is exposed without the surface layer functioning as an insulating layer, and the effect of suppressing the short circuit between the positive and negative electrodes is not sufficiently exhibited.
　本発明は、釘のような異物によって内部短絡が起こり、負極に大きな応力が印加される場合でも、電池温度の過度の上昇を抑制でき、優れた安全性を有する非水電解質二次電池用負極を提供することを目的とする。 The present invention provides a negative electrode for a non-aqueous electrolyte secondary battery that can suppress an excessive increase in battery temperature and has excellent safety even when an internal short circuit occurs due to a foreign substance such as a nail and a large stress is applied to the negative electrode. The purpose is to provide.
　本発明の一局面は、集電体、前記集電体の表面に付着した第１層および前記第１層の表面に付着した第２層を備え、前記第１層が、無機酸化物粒子および第１結着剤を含み、前記第２層が、リチウムイオンを可逆的に吸蔵および放出可能な炭素材料および第２結着剤を含み、前記第１層の厚さＴ1と、前記第２層の厚さＴ2とが、Ｔ1＜Ｔ2を満たす、非水電解質二次電池用負極に関する。 One aspect of the present invention includes a current collector, a first layer attached to a surface of the current collector, and a second layer attached to a surface of the first layer, wherein the first layer includes inorganic oxide particles and Including a first binder, and the second layer includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder, the thickness T 1 of the first layer, and the second layer The layer thickness T 2 relates to a negative electrode for a non-aqueous electrolyte secondary battery in which T 1 <T 2 is satisfied.
　本発明の他の一局面は、正極、負極および正極と負極との間に介在するセパレータおよび非水電解質を含み、負極が、上記の非水電解質二次電池用負極である、非水電解質二次電池に関する。 Another aspect of the present invention includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein the negative electrode is the negative electrode for a non-aqueous electrolyte secondary battery described above. Next battery.
　本発明によれば、内部短絡が起こり、負極に大きな応力が印加される場合でも、電池温度の過度の上昇を抑制でき、優れた安全性を有する非水電解質二次電池用負極を提供することができる。 According to the present invention, even when an internal short circuit occurs and a large stress is applied to the negative electrode, an excessive increase in battery temperature can be suppressed, and a negative electrode for a nonaqueous electrolyte secondary battery having excellent safety is provided. Can do.
　本発明の新規な特徴を添付の請求の範囲に記述するが、本発明は、構成および内容の両方に関し、本発明の他の目的および特徴と併せ、図面を照合した以下の詳細な説明によりさらによく理解されるであろう。 While the novel features of the invention are set forth in the appended claims, the invention will be further described by reference to the following detailed description, taken in conjunction with the other objects and features of the invention, both in terms of construction and content. It will be well understood.
本発明の一実施形態に係る非水電解質二次電池用負極の構成を概略的に示す縦断面図である。It is a longitudinal cross-sectional view which shows schematically the structure of the negative electrode for nonaqueous electrolyte secondary batteries which concerns on one Embodiment of this invention. 本発明の一実施形態に係る非水電解質二次電池の構成を概略的に示す縦断面図である。1 is a longitudinal sectional view schematically showing a configuration of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.
　非水電解質二次電池用負極は、集電体と、集電体の表面に付着した負極合剤層とを有する。釘などの比較的大きな異物によって負極が破壊されるなどして、負極に大きな応力が印加されると、従来の負極では、負極合剤層が剥がれて集電体が露出することがある。その結果、正極と負極との絶縁を保つことが困難となり、内部短絡の拡大および電池温度の過度の上昇を招く。 The negative electrode for a non-aqueous electrolyte secondary battery has a current collector and a negative electrode mixture layer attached to the surface of the current collector. When a large stress is applied to the negative electrode, for example, when the negative electrode is broken by a relatively large foreign object such as a nail, in the conventional negative electrode, the negative electrode mixture layer may be peeled off to expose the current collector. As a result, it becomes difficult to maintain insulation between the positive electrode and the negative electrode, leading to an expansion of internal short circuit and an excessive increase in battery temperature.
　そこで、本発明者が鋭意研究を行った結果、集電体の表面に厚さの小さい高抵抗層を配置することにより、負極に大きな応力が印加されても高抵抗層が集電体から剥がれにくく、優れた安全性が得られることがわかった。 Therefore, as a result of intensive research conducted by the present inventors, by arranging a high resistance layer with a small thickness on the surface of the current collector, the high resistance layer is peeled off from the current collector even when a large stress is applied to the negative electrode. It was difficult to obtain excellent safety.
　本発明に係る非水電解質二次電池用負極は、集電体と、無機酸化物粒子および第１結着剤を含む第１層と、リチウムイオンを可逆的に吸蔵および放出可能な炭素材料および第２結着剤を含む第２層とを備える。第１層は、高抵抗層として機能し、第２層は、電池反応を担う負極合剤層として機能する。また、第１層にリチウムイオンを可逆的に吸蔵および放出可能な無機酸化物粒子を含ませることで、第１層を高抵抗層のみならず、電池反応を担う負極合剤層として機能させることもできる。 A negative electrode for a non-aqueous electrolyte secondary battery according to the present invention includes a current collector, a first layer containing inorganic oxide particles and a first binder, a carbon material capable of reversibly occluding and releasing lithium ions, and And a second layer containing a second binder. The first layer functions as a high resistance layer, and the second layer functions as a negative electrode mixture layer responsible for battery reaction. In addition, by including inorganic oxide particles capable of reversibly occluding and releasing lithium ions in the first layer, the first layer functions not only as a high resistance layer but also as a negative electrode mixture layer responsible for battery reaction. You can also.
　本発明において、第１層は、電極反応を担う役割がなく、あるいはその役割が小さいため、リチウムイオンの受け入れ性を考慮する必要性が小さい。したがって、第１層は、比較的多量の第１結着剤を含ませることができる。また、第１層は比較的薄く形成されている。そのため、万一負極に大きな応力が印加されても、第１層が集電体から剥がれにくい。よって、内部短絡の拡大や電池温度の過度の上昇を抑制でき、非水電解質二次電池の安全性が向上する。 In the present invention, the first layer does not have a role to play an electrode reaction or has a small role, so that it is not necessary to consider the acceptability of lithium ions. Accordingly, the first layer can contain a relatively large amount of the first binder. The first layer is formed relatively thin. Therefore, even if a large stress is applied to the negative electrode, the first layer is difficult to peel off from the current collector. Therefore, expansion of the internal short circuit and excessive increase in battery temperature can be suppressed, and the safety of the nonaqueous electrolyte secondary battery is improved.
　図１は、本発明の一実施形態に係る非水電解質二次電池用負極の構成を概略的に示す縦断面図である。負極１０は、集電体１１の表面に付着した第１層１２および第１層１２の表面に付着した第２層１３を備える。第１層は、無機酸化物粒子および第１結着剤を含み、第２層１３は、リチウムイオンを可逆的に吸蔵および放出可能な炭素材料および第２結着剤を含む。 FIG. 1 is a longitudinal sectional view schematically showing a configuration of a negative electrode for a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. The negative electrode 10 includes a first layer 12 attached to the surface of the current collector 11 and a second layer 13 attached to the surface of the first layer 12. The first layer includes inorganic oxide particles and a first binder, and the second layer 13 includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder.
　本発明においては、第１層１２の厚さＴ1と、第２層１３の厚さＴ2とが、Ｔ1＜Ｔ2を満たす。Ｔ1とＴ2との比：Ｔ1／Ｔ2を１より小さくすることで、高抵抗層であるＴ1の放電特性への影響を抑制することができ、負極全体のエネルギー密度を十分に確保することも可能となる。Ｔ1／Ｔ2は、０．１５以上、０．８以下であることが好ましく、０．５５以下であることがより好ましい。Ｔ1／Ｔ2を０．１５以上とすることで、異常時に電池温度の過度の上昇を防ぐことが容易となる。一方、Ｔ1／Ｔ2を０．８以下、好ましくは０．５５以下とすることで、集電体と第１層との密着性を十分に確保しつつ、負極全体のエネルギー密度を十分に確保することができる。 In the present invention, the thickness T 1 of the first layer 12, the thickness T 2 of the second layer 13 satisfies T 1 <T 2. Ratio of T 1 and T 2 : By making T 1 / T 2 smaller than 1 , the influence on the discharge characteristics of T 1 which is a high resistance layer can be suppressed, and the energy density of the entire negative electrode is sufficiently increased It can also be secured. T 1 / T 2 is preferably 0.15 or more and 0.8 or less, and more preferably 0.55 or less. By setting T 1 / T 2 to 0.15 or more, it becomes easy to prevent an excessive increase in battery temperature during an abnormality. On the other hand, by setting T 1 / T 2 to 0.8 or less, preferably 0.55 or less, the energy density of the entire negative electrode is sufficiently ensured while sufficiently securing the adhesion between the current collector and the first layer. Can be secured.
　第１層１２の厚さＴ1は、１～４０μｍであることが好ましく、１～３０μｍであることがより好ましい。Ｔ1を１μｍ以上とすることで、短絡時に、第１層に、高抵抗層としての機能を十分に発揮させることができる。一方、Ｔ1を４０μｍ以下とすることで、集電体との密着性やエネルギー密度を十分に確保することができる。第２層１３の厚さＴ2は、５０～１００μｍであることが好ましい。Ｔ2を５０μｍ以上とすることで、より高いエネルギー密度を確保することができる。一方、Ｔ2を１００μｍ以下とすることで、より良好なリチウムイオン受け入れ性を得ることができる。 The thickness T 1 of the first layer 12 is preferably 1 to 40 μm, and more preferably 1 to 30 μm. By setting T 1 to 1 μm or more, the first layer can sufficiently exhibit the function as the high resistance layer at the time of a short circuit. On the other hand, when T 1 is set to 40 μm or less, adhesion to the current collector and energy density can be sufficiently ensured. The thickness T 2 of the second layer 13 is preferably 50 to 100 μm. By setting T 2 to 50 μm or more, a higher energy density can be secured. On the other hand, by setting T 2 to 100 μm or less, better lithium ion acceptability can be obtained.
　第１層の密度は、１～５ｇ／ｃｍ3が好ましく、１．５～４ｇ／ｃｍ3がより好ましい。第２層の密度は、１．２～１．７ｇ／ｃｍ3が好ましく、１．３～１．６ｇ／ｃｍ3がより好ましい。第１層および第２層の密度をそれぞれ上記範囲とすることで、より良好なリチウムイオンの受け入れ性を得ることができるとともに、負極全体のエネルギー密度を十分に確保することができる。 Density of the first layer is preferably 1 ~ 5 g / cm 3, more preferably 1.5 ~ 4g / cm 3. Density of the second layer is preferably 1.2 ~ 1.7g / cm 3, more preferably 1.3 ~ 1.6g / cm 3. By setting the densities of the first layer and the second layer in the above ranges, better lithium ion acceptability can be obtained, and the energy density of the entire negative electrode can be sufficiently secured.
　無機酸化物粒子としては、アルミナ、シリカ、マグネシアなどの、リチウムイオンを吸蔵および放出しない絶縁性無機酸化物粒子を用いてもよく、層状、スピネル型等の結晶構造を有する、リチウムイオンを可逆的に吸蔵および放出可能な無機酸化物粒子を用いてもよい。なかでも、集電体と第２層との導通を容易に確保できることから、リチウムイオンを可逆的に吸蔵および放出可能な無機酸化物粒子を用いることが好ましい。リチウムイオンを可逆的に吸蔵および放出可能な無機酸化物粒子を含む第１層は、通常時には、電池反応を担う負極合剤層として機能し、電池の内部短絡が発生すると、リチウムイオンを放出して高抵抗層として機能する。これにより、高いエネルギー密度を維持しつつ、内部短絡の拡大や電池温度の過度の上昇を抑制できる。 As the inorganic oxide particles, insulating inorganic oxide particles that do not occlude and release lithium ions, such as alumina, silica, and magnesia, may be used, and the lithium ions having a layered or spinel crystal structure are reversible. Alternatively, inorganic oxide particles that can be occluded and released may be used. Among them, it is preferable to use inorganic oxide particles capable of reversibly occluding and releasing lithium ions, since electrical conduction between the current collector and the second layer can be easily secured. The first layer containing inorganic oxide particles capable of reversibly occluding and releasing lithium ions normally functions as a negative electrode mixture layer responsible for battery reaction, and releases lithium ions when an internal short circuit of the battery occurs. Function as a high resistance layer. Thereby, expansion of an internal short circuit and the excessive raise of battery temperature can be suppressed, maintaining a high energy density.
　リチウムイオンを可逆的に吸蔵および放出可能な無機酸化物粒子は、リチウムイオン吸蔵時に電子伝導性を有することから、スピネル型の結晶構造を有するチタン酸リチウムを含むことが好ましい。チタン酸リチウムは、リチウムイオンの受け入れ性が高く、負極の拡散抵抗を低減しやすい。このような無機酸化物粒子を含む第１層は、負極電位が金属リチウムに対して高い領域（すなわち、充電初期）においてリチウムの吸蔵が起こりやすい。そのため、第１結着剤の量を比較的多くしても、十分なリチウムイオンの受け入れ性を維持することが容易である。すなわち、集電体と第１層との密着性と、負極全体のリチウムイオンの受け入れ性とを高いレベルで両立できる。 It is preferable that the inorganic oxide particles capable of reversibly occluding and releasing lithium ions include lithium titanate having a spinel crystal structure because it has electronic conductivity when occluding lithium ions. Lithium titanate has high acceptability of lithium ions and can easily reduce the diffusion resistance of the negative electrode. The first layer containing such inorganic oxide particles is liable to occlude lithium in a region where the negative electrode potential is higher than that of metallic lithium (that is, in the initial stage of charging). Therefore, even if the amount of the first binder is relatively large, it is easy to maintain sufficient lithium ion acceptability. That is, the adhesion between the current collector and the first layer and the lithium ion acceptability of the entire negative electrode can be achieved at a high level.
　また、チタン酸リチウムは、リチウムイオンを吸蔵していない状態では導電性を有さず、炭素材料に比べて熱安定性が高い。そのため、万一電池の内部短絡が発生した場合には、正負極間の絶縁を保つことができ、発熱も抑制される。よって、内部短絡の拡大および電池温度の過度の上昇をより確実に抑制できる。典型的なチタン酸リチウムは、一般式：Ｌｉ4Ｔｉ5Ｏ12で表される。ただし、一般式：ＬｉxＴｉ5-yＭyＯ12+z（ただし、元素Ｍはバナジウム、マンガン、鉄、コバルト、ニッケル、銅、亜鉛、アルミニウム、ホウ素、マグネシウム、カルシウム、ストロンチウム、バリウム、ジルコニウム、ニオブ、モリブデン、タングステン、ビスマス、ナトリウム、ガリウムおよび希土類元素よりなる群から選択される少なくとも１種であり、ｘ、ｙおよびｚは、それぞれ３≦ｘ≦５、０≦ｙ≦１．５、好ましくは０．００５≦ｙ≦１．５、－１≦ｚ≦１を満たす。ｘは合成直後または完全放電状態における値である）で表されるチタン酸リチウムも同様に用いることができる。 In addition, lithium titanate does not have conductivity in a state where lithium ions are not occluded, and has higher thermal stability than a carbon material. Therefore, in the unlikely event that an internal short circuit of the battery occurs, insulation between the positive and negative electrodes can be maintained, and heat generation is also suppressed. Therefore, expansion of the internal short circuit and excessive increase of the battery temperature can be more reliably suppressed. A typical lithium titanate is represented by the general formula: Li 4 Ti 5 O 12 . However, the general formula: Li x Ti 5-y M y O 12 + z ( where element M is vanadium, manganese, iron, cobalt, nickel, copper, zinc, aluminum, boron, magnesium, calcium, strontium, barium, zirconium , Niobium, molybdenum, tungsten, bismuth, sodium, gallium and rare earth elements, and x, y and z are 3 ≦ x ≦ 5, 0 ≦ y ≦ 1.5, respectively. Preferably, 0.005 ≦ y ≦ 1.5 and −1 ≦ z ≦ 1 are satisfied, and x is a value immediately after synthesis or in a fully discharged state).
　無機酸化物粒子の平均粒径（体積基準の粒度分布におけるメディアン径：Ｄ50）は、０．１～５μｍであることが好ましい。平均粒径が上記範囲に含まれる場合、例えばチタン酸リチウムでは、リチウムイオンの受け入れ性が特に高くなる。無機酸化物粒子の体積基準の粒度分布は、例えば市販のレーザー回折式の粒度分布測定装置により測定することができる。 The average particle diameter of the inorganic oxide particles (median diameter in the volume-based particle size distribution: D 50 ) is preferably 0.1 to 5 μm. When the average particle size is included in the above range, for example, lithium titanate has particularly high lithium ion acceptability. The volume-based particle size distribution of the inorganic oxide particles can be measured by, for example, a commercially available laser diffraction particle size distribution measuring device.
　無機酸化物粒子のＢＥＴ比表面積は、０．５～２０ｍ2／ｇであることが好ましい。ＢＥＴ比表面積が上記範囲に含まれる場合、例えばチタン酸リチウムでは、リチウムイオンの受け入れ性が特に高くなる。 The BET specific surface area of the inorganic oxide particles is preferably 0.5 to 20 m 2 / g. When the BET specific surface area is included in the above range, for example, lithium titanate has particularly high lithium ion acceptability.
　第１結着剤としては、例えば、フッ素樹脂、ポリオレフィン樹脂、アクリル樹脂、ゴム弾性を有する粒子状の結着剤などが挙げられる。フッ素樹脂としては、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリヘキサフルオロプロピレンなどが挙げられる。ポリオレフィン樹脂としては、ポリエチレン、ポリプロピレンなどが挙げられる。アクリル樹脂としては、ポリアクリルニトリル、ポリアクリル酸、ポリアクリル酸メチルエステル、ポリアクリル酸エチルエステル、ポリアクリル酸ヘキシルエステル、ポリメタクリル酸、ポリメタクリル酸メチルエステル、ポリメタクリル酸エチルエステル、ポリメタクリル酸ヘキシルエステルなどが挙げられる。ゴム弾性を有する粒子状の結着剤としては、スチレンブタジエンゴムなどが挙げられる。その他の第１結着剤としては、アラミド樹脂、ポリアミド、ポリイミド、ポリアミドイミド、ポリ酢酸ビニル、ポリビニルピロリドン、ポリエーテル、ポリエーテルサルフォン、カルボキシメチルセルロースなどが挙げられる。第１結着剤は、１種のみを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。 Examples of the first binder include a fluororesin, a polyolefin resin, an acrylic resin, and a particulate binder having rubber elasticity. Examples of the fluororesin include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene, and the like. Examples of the polyolefin resin include polyethylene and polypropylene. Acrylic resins include polyacrylonitrile, polyacrylic acid, polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid hexyl ester, polymethacrylic acid, polymethacrylic acid methyl ester, polymethacrylic acid ethyl ester, polymethacrylic acid. Examples include hexyl esters. Examples of the particulate binder having rubber elasticity include styrene butadiene rubber. Examples of other first binders include aramid resin, polyamide, polyimide, polyamideimide, polyvinyl acetate, polyvinyl pyrrolidone, polyether, polyethersulfone, carboxymethylcellulose, and the like. A 1st binder may be used individually by 1 type, and may be used in combination of 2 or more type.
　また、テトラフルオロエチレン、ヘキサフルオロプロピレン、パーフルオロアルキルビニルエーテル、フッ化ビニリデン、クロロトリフルオロエチレン、エチレン、プロピレン、ペンタフルオロプロピレン、フルオロメチルビニルエーテル、アクリル酸およびヘキサジエンよりなる群から選択される２種以上の単位の共重合体を、第１結着剤として用いてもよい。 Also, two or more selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid and hexadiene A copolymer of these units may be used as the first binder.
　第１結着剤の量Ｗ1は、集電体１１と第１層１２との十分な密着性を確保できる範囲であれば特に限定されないが、例えば、無機酸化物粒子１００質量部あたり、０．５～１０質量部であることが好ましく、３～７質量部であることが特に好ましい。これにより、集電体と第１層との密着性を十分に確保できる。また、リチウムイオンを可逆的に吸蔵および放出可能な無機酸化物粒子を用いる場合に、集電体との密着性と、リチウムイオン受け入れ性とを高いレベルで両立することができる。 The amount W 1 of the first binder is not particularly limited as long as sufficient adhesion between the current collector 11 and the first layer 12 can be secured. For example, the amount W 1 is 0 per 100 parts by mass of the inorganic oxide particles. The amount is preferably 5 to 10 parts by mass, particularly preferably 3 to 7 parts by mass. Thereby, sufficient adhesion between the current collector and the first layer can be ensured. Further, when inorganic oxide particles capable of reversibly occluding and releasing lithium ions are used, both the adhesion to the current collector and the lithium ion acceptability can be achieved at a high level.
　第１層に含まれる第１結着剤の量Ｗ1は、第２層に含まれる第２結着剤の量Ｗ2より多いことが好ましく、Ｗ1とＷ2との比：Ｗ1／Ｗ2が、３～１０を満たすことがより好ましい。これにより、集電体と第１層との密着性と、負極全体のエネルギー密度とをより高いレベルで両立することができる。 The amount W 1 of the first binder contained in the first layer is preferably larger than the amount W 2 of the second binder contained in the second layer, and the ratio of W 1 and W 2 : W 1 / More preferably, W 2 satisfies 3 to 10. Thereby, the adhesiveness of a collector and a 1st layer and the energy density of the whole negative electrode can be made compatible at a higher level.
　第１層１２は、更に導電材を含んでもよい。これにより、集電体１１と第２層１３との導通をより容易に確保することができる。具体的な導電材としては、例えば、各種天然黒鉛や各種人造黒鉛などの黒鉛粒子、アセチレンブラック、ケッチェンブラック、チャンネルブラック、ファーネスブラック、ランプブラックまたはサーマルブラックなどのカーボンブラック類、炭素繊維、金属繊維などの導電性繊維類、フッ化カーボンなどが挙げられる。第１層における導電材の量は特に限定されないが、集電体と第２層１３との導通を確保しつつ、内部短絡の際に第１層を高抵抗層として機能させる観点から、例えば、無機酸化物粒子１００質量部あたり、１～５質量部であることが好ましい。 The first layer 12 may further contain a conductive material. Thereby, conduction between the current collector 11 and the second layer 13 can be more easily ensured. Specific conductive materials include, for example, graphite particles such as various natural graphites and various artificial graphites, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black or thermal black, carbon fiber, metal Examples thereof include conductive fibers such as fibers and carbon fluoride. Although the amount of the conductive material in the first layer is not particularly limited, for example, from the viewpoint of functioning the first layer as a high resistance layer in the case of an internal short circuit while ensuring electrical continuity between the current collector and the second layer 13, for example, The amount is preferably 1 to 5 parts by mass per 100 parts by mass of the inorganic oxide particles.
　第２層１３は、リチウムイオンを可逆的に吸蔵および放出可能な炭素材料および第２結着剤を含む。リチウムイオンを可逆的に吸蔵および放出可能な炭素材料としては、例えば各種天然黒鉛や各種人造黒鉛などの黒鉛粒子、コークス、ハードカーボン、ソフトカーボン、黒鉛化途上炭素、炭素繊維、球状炭素、非晶質炭素などが挙げられる。なかでも、高容量の負極が得られやすい観点から、黒鉛粒子を用いることが好ましい。 The second layer 13 includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder. Examples of carbon materials capable of reversibly occluding and releasing lithium ions include graphite particles such as various natural graphites and various artificial graphites, coke, hard carbon, soft carbon, graphitized carbon, carbon fiber, spherical carbon, and amorphous. Carbon. Among these, graphite particles are preferably used from the viewpoint of easily obtaining a high-capacity negative electrode.
　上記の炭素材料の平均粒径（体積基準の粒度分布におけるメディアン径：Ｄ50）は、５～３０μｍであることが好ましい。平均粒径が上記範囲に含まれる場合、例えば黒鉛粒子では、第２層における粒子の滑り性が向上し、充填状態を良好にしやすい点で有利である。炭素材料の体積基準の粒度分布は、例えば市販のレーザー回折式の粒度分布測定装置により測定することができる。 The average particle diameter (median diameter in volumetric particle size distribution: D 50 ) of the carbon material is preferably 5 to 30 μm. When the average particle size is included in the above range, for example, graphite particles are advantageous in that the sliding property of the particles in the second layer is improved and the filling state is easily improved. The volume-based particle size distribution of the carbon material can be measured by, for example, a commercially available laser diffraction particle size distribution measuring apparatus.
　上記の炭素材料のＢＥＴ比表面積は、２～６ｍ2／ｇであることが好ましい。ＢＥＴ比表面積が上記範囲に含まれる場合、例えば黒鉛粒子では、第２層における粒子の滑り性が向上し、充填状態を良好にしやすい点で有利である。 The carbon material preferably has a BET specific surface area of 2 to 6 m 2 / g. When the BET specific surface area is included in the above range, for example, graphite particles are advantageous in that the sliding property of the particles in the second layer is improved and the filling state is easily improved.
　第２層１３は、上記の炭素材料に加えて、珪素（Ｓｉ）もしくは錫（Ｓｎ）などの単体またはこれらの元素を含む合金、珪素化合物（例えば、ＳｉＯx（０＜ｘ＜２）で表される珪素酸化物、珪素を含む固溶体など）、錫化合物（例えば、錫を含む固溶体）などを含んでいてもよい。 In addition to the above carbon material, the second layer 13 is composed of a simple substance such as silicon (Si) or tin (Sn), an alloy containing these elements, or a silicon compound (for example, SiO x (0 <x <2)). Or a solid solution containing silicon, a tin compound (eg, a solid solution containing tin), or the like.
　第２結着剤としては、例えば、第１結着剤として例示したものから１種以上を任意に選択して用いることができる。第２結着剤の量は、例えば、上記の炭素材料１００質量部あたり、０．４～１．５質量部であることが好ましい。 As the second binder, for example, one or more kinds of those exemplified as the first binder can be arbitrarily selected and used. The amount of the second binder is preferably 0.4 to 1.5 parts by mass per 100 parts by mass of the carbon material, for example.
　集電体１１の材質は特に限定されないが、銅箔、銅合金箔、ニッケル箔などが好ましい。集電体の厚さは、例えば５～３０μｍであるが、特に限定されない。 The material of the current collector 11 is not particularly limited, but copper foil, copper alloy foil, nickel foil and the like are preferable. The thickness of the current collector is, for example, 5 to 30 μm, but is not particularly limited.
　非水電解質二次電池用負極の製造方法は特に限定されない。例えば、無機酸化物粒子と第１結着剤と分散媒とを含む第１層用スラリーと、炭素材料と第２結着剤と分散媒とを含む第２層用スラリーとを調製する。集電体の表面に第１層用スラリーを塗布し、乾燥させて、任意の厚さに圧延して第１層を形成する。その後、第１層の表面に第２層用スラリーを塗布し、乾燥させて、任意の厚さに圧延して第２層を形成することで、負極が得られる。吐出スリットを２つ以上具備するダイコータ等を用いて、第１層用スラリーと第２層用スラリーとを、同時に塗布し、乾燥させてもよい。 The method for producing the negative electrode for the nonaqueous electrolyte secondary battery is not particularly limited. For example, a first layer slurry containing inorganic oxide particles, a first binder, and a dispersion medium, and a second layer slurry containing a carbon material, a second binder, and a dispersion medium are prepared. The first layer slurry is applied to the surface of the current collector, dried, and rolled to an arbitrary thickness to form the first layer. Then, the negative electrode is obtained by apply | coating the slurry for 2nd layers to the surface of a 1st layer, making it dry, rolling to arbitrary thickness, and forming a 2nd layer. Using a die coater or the like having two or more discharge slits, the first layer slurry and the second layer slurry may be simultaneously applied and dried.
　次に、上記の非水電解質二次電池用負極を含む非水電解質二次電池について説明する。
　非水電解質二次電池は、正極、負極、正極と負極の間に介在するセパレータおよび非水電解質を含む。 Next, a non-aqueous electrolyte secondary battery including the above negative electrode for a non-aqueous electrolyte secondary battery will be described.
The non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte.
　正極は、集電体と、集電体の表面に付着した正極合剤層とを備える。正極合剤層は、正極活物質を必須成分として含み、結着剤、導電材などを任意成分として含む。
　正極活物質としては、リチウム複合金属酸化物を用いることができる。リチウム複合金属酸化物としては、例えば、ＬｉxＣｏＯ2、ＬｉｘＮｉＯ2、ＬｉxＭｎＯ2、ＬｉxＣｏyＮｉ1-yＯ2、ＬｉxＣｏyＭ1-yＯz、ＬｉxＮｉ1-yＭyＯz、ＬｉxＭｎ2Ｏ4、ＬｉxＭｎ2-yＭyＯ4、ＬｉＭＰＯ4、Ｌｉ2ＭＰＯ4Ｆ（Ｍ＝Ｎａ、Ｍｇ、Ｓｃ、Ｙ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｚｎ、Ａｌ、Ｃｒ、Ｐｂ、ＳｂおよびＢのうち少なくとも１種）などが挙げられる。ただし、０＜ｘ≦１．２、０＜ｙ≦０．９、２≦ｚ≦２．３を満たす。なお、リチウムのモル比を示すｘ値は、活物質作製直後の値であり、充放電により増減する。
　リチウム複合金属酸化物は、金属元素の一部が異種元素で置換されたものであってもよい。さらに、リチウム複合金属酸化物は、金属酸化物、リチウム酸化物または導電剤などで表面処理されていてもよく、表面が疎水化処理されていてもよい。 The positive electrode includes a current collector and a positive electrode mixture layer attached to the surface of the current collector. The positive electrode mixture layer includes a positive electrode active material as an essential component, and includes a binder, a conductive material, and the like as optional components.
A lithium composite metal oxide can be used as the positive electrode active material. Examples of the lithium composite metal oxide include Li x CoO 2 , Li x NiO 2 , Li x MnO 2 , Li x Co y Ni 1 -y O 2 , Li x Co y M 1 -y O z , and Li x Ni. 1-y M y O z, Li x Mn 2 O 4, Li x Mn 2-y M y O 4, LiMPO 4, Li 2 MPO 4 F (M = Na, Mg, Sc, Y, Mn, Fe, Co , Ni, Cu, Zn, Al, Cr, Pb, Sb, and B). However, 0 <x ≦ 1.2, 0 <y ≦ 0.9, and 2 ≦ z ≦ 2.3 are satisfied. In addition, x value which shows the molar ratio of lithium is a value immediately after active material preparation, and increases / decreases by charging / discharging.
The lithium composite metal oxide may have a metal element partially substituted with a different element. Further, the lithium composite metal oxide may be surface-treated with a metal oxide, lithium oxide, a conductive agent, or the like, and the surface may be subjected to a hydrophobic treatment.
　セパレータとしては、例えばポリオレフィン製の微多孔質フィルムを好適に用いることができる。
非水電解質は、非水溶媒およびこれに溶解する溶質を含む。非水溶媒としては、例えば、エチレンカーボネ－ト（ＥＣ）、プロピレンカーボネ－ト（ＰＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）およびエチルメチルカーボネート（ＥＭＣ）が挙げられるが、これらに限定されない。非水溶媒は１種のみを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。溶質としては、例えば、ＬｉＢＦ4、ＬｉＰＦ6、ＬｉＡｌＣｌ4、ＬｉＣｌ、リチウムイミド塩などのリチウム塩が挙げられる。溶質は１種のみを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。 As the separator, for example, a microporous film made of polyolefin can be suitably used.
The non-aqueous electrolyte includes a non-aqueous solvent and a solute that dissolves therein. Nonaqueous solvents include, for example, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). It is not limited to. A non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type. Examples of the solute include lithium salts such as LiBF 4 , LiPF 6 , LiAlCl 4 , LiCl, and lithium imide salt. Only one solute may be used alone, or two or more solutes may be used in combination.
　以下、本発明を実施例および比較例に基づいてより詳細に説明する。 Hereinafter, the present invention will be described in more detail based on examples and comparative examples.
　《実施例１》
（i）負極の作製
（第１層）
　スピネル型の結晶構造を有するチタン酸リチウム（Ｌｉ4Ｔｉ5Ｏ12、平均粒径１μｍ、ＢＥＴ比表面積３ｍ２／ｇ）２ｋｇと、人造黒鉛（平均粒径１０μｍ）５０ｇと、日本ゼオン（株）製のＢＭ－４００Ｂ（固形分４０質量％の変性スチレン－ブタジエンゴムの分散液）１００ｇと、カルボキシメチルセルロース（ＣＭＣ）５０ｇと、分散媒である適量の水とを、双腕式練合機にて攪拌し、チタン酸リチウムを含む第１層用スラリーを調製した。得られた第１層用スラリーを、厚さ１０μｍの銅箔からなる負極用の集電体の両面に塗布し、乾燥し、総厚が３０μｍとなるように圧延して、第１層を形成した。すなわち、第１層の厚さ（Ｔ１）は、銅箔の片面あたり１０μｍとした。第１層の密度は２ｇ／ｃｍ３とした。 Example 1
(I) Production of negative electrode (first layer)
2 kg of lithium titanate having a spinel crystal structure (Li 4 Ti 5 O 12 , average particle size 1 μm, BET specific surface area 3 m 2 / g), artificial graphite (average particle size 10 μm) 50 g, Nippon Zeon Co., Ltd. 100 g of BM-400B (modified styrene-butadiene rubber dispersion having a solid content of 40% by mass), 50 g of carboxymethylcellulose (CMC), and an appropriate amount of water as a dispersion medium were mixed in a double-arm kneader. The mixture was stirred to prepare a first layer slurry containing lithium titanate. The obtained first layer slurry is applied to both sides of a negative electrode current collector made of a copper foil having a thickness of 10 μm, dried, and rolled to a total thickness of 30 μm to form a first layer. did. That is, the thickness (T 1 ) of the first layer was 10 μm per one side of the copper foil. The density of the first layer was 2 g / cm 3 .
（第２層）
　人造黒鉛（平均粒径１０μｍ、ＢＥＴ比表面積３ｍ２／ｇ）３ｋｇと、日本ゼオン（株）製のＢＭ－４００Ｂ（固形分４０質量％の変性スチレン－ブタジエンゴムの分散液）７５ｇと、カルボキシメチルセルロース（ＣＭＣ）３０ｇと、分散媒である適量の水とを、双腕式練合機にて攪拌し、黒鉛を含む第２層用スラリーを調製した。得られた第２層用スラリーを、銅箔の両面に付着した第１層の表面にそれぞれ塗布し、乾燥し、総厚が１６０μｍとなるように圧延して、第２層を形成した。第２層の厚さ（Ｔ２）は、片面あたり６５μｍであった。第２層の密度は１．５ｇ／ｃｍ３とした。 (Second layer)
3 kg of artificial graphite (average particle size 10 μm, BET specific surface area 3 m 2 / g), 75 g of BM-400B (modified styrene-butadiene rubber dispersion having a solid content of 40% by mass) manufactured by Nippon Zeon Co., Ltd., and carboxymethylcellulose (CMC) 30 g and an appropriate amount of water as a dispersion medium were stirred with a double-arm kneader to prepare a slurry for the second layer containing graphite. The obtained slurry for the second layer was applied to the surface of the first layer adhered to both surfaces of the copper foil, dried, and rolled to a total thickness of 160 μm to form a second layer. The thickness (T 2 ) of the second layer was 65 μm per side. The density of the second layer was 1.5 g / cm 3 .
　得られた極板を幅５８ｍｍ、長さ７５０ｍｍに裁断し、Ｔ１／Ｔ２が０．１５である負極を得た。 The obtained electrode plate was cut into a width of 58 mm and a length of 750 mm to obtain a negative electrode having T 1 / T 2 of 0.15.
（ii）正極の作製
　コバルト酸リチウム（ＬｉＣｏＯ2、平均粒径１０μｍ）３ｋｇと、ＰＶＤＦを１２質量％含むＮ－メチル－２－ピロリドン（ＮＭＰ）溶液（（株）クレハ製のＰＶＤＦ＃１３２０）１ｋｇと、アセチレンブラック９０ｇと、分散媒である適量のＮＭＰとを、双腕式練合機で攪拌し、正極合剤スラリーを調製した。得られた正極合剤スラリーを、厚さ１５μｍのアルミニウム箔からなる正極集電体の両面に塗布し、乾燥し、総厚が１２０μｍとなるように圧延して、正極合剤層を形成した。正極合剤層の厚さは、片面あたり５２．５μｍであった。得られた極板を幅５６ｍｍ、長さ７００ｍｍに裁断し、正極を得た。 (Ii) Production of positive electrode 3 kg of lithium cobaltate (LiCoO 2 , average particle diameter 10 μm) and 1 kg of N-methyl-2-pyrrolidone (NMP) solution containing 12% by mass of PVDF (PVDF # 1320 manufactured by Kureha Corporation) Then, 90 g of acetylene black and an appropriate amount of NMP as a dispersion medium were stirred with a double-arm kneader to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 15 μm, dried, and rolled to a total thickness of 120 μm to form a positive electrode mixture layer. The thickness of the positive electrode mixture layer was 52.5 μm per side. The obtained electrode plate was cut into a width of 56 mm and a length of 700 mm to obtain a positive electrode.
（iii）非水電解質の調製
　エチレンカーボネート（ＥＣ）と、ジメチルカーボネート（ＤＭＣ）と、エチルメチルカーボネート（ＥＭＣ）との体積比１：１：１の混合溶媒に、１モル／リットルの濃度でＬｉＰＦ６を溶解させ、さらに全体の３質量％相当のビニレンカーボネート（ＶＣ）を添加して、非水電解質を得た。 (Iii) Preparation of nonaqueous electrolyte LiPF at a concentration of 1 mol / liter in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 1: 1: 1. 6 was dissolved, and further vinylene carbonate (VC) corresponding to 3% by mass of the whole was added to obtain a non-aqueous electrolyte.
（iv）電池の作製
　以下に示す手順で図２に示す円筒型電池を作製した。 (Iv) Production of Battery The cylindrical battery shown in FIG. 2 was produced by the following procedure.
　上記（i）および（ii）で作製した正極２５と負極２６とを、これらの間に介在させたセパレータ２７（厚さ２０μｍのポリエチレン製の微多孔質フィルム）とともに捲回し、円柱状の電極群を構成した。ニッケルめっきを施した鉄製の有底円筒型の電池ケース２１（直径１８ｍｍ、高さ６５ｍｍ、内径１７．８５ｍｍ）の内部に電極群を収容した。なお、電極群の長手方向の両端には、それぞれ上部絶縁板２８ａおよび下部絶縁板２８ｂを配置した。正極２５にはアルミニウム製の正極リード２５ａの一端を接続し、他端を封口板２２の下面に接続した。負極２６にはニッケル製の負極リード２６ａの一端を接続し、他端を電池ケース２１の内底面に接続した。その後、電池ケース２１の内部に非水電解質を５．５ｇ注入し、電極群に非水電解質を含浸させた。次に、電池ケース２１の開口に封口板２２を配置し、電池ケース２１の開口端部を封口板２２の周縁部にガスケット２３を介してかしめた。このようにして、設計容量２１５０ｍＡｈの円筒型非水電解質二次電池（電池Ａ）を作製した。 The positive electrode 25 and the negative electrode 26 produced in the above (i) and (ii) are wound together with a separator 27 (20 μm-thick polyethylene microporous film) interposed between them to form a cylindrical electrode group Configured. An electrode group was housed inside a nickel-plated bottomed cylindrical battery case 21 (diameter 18 mm, height 65 mm, inner diameter 17.85 mm). An upper insulating plate 28a and a lower insulating plate 28b are disposed at both ends in the longitudinal direction of the electrode group. One end of an aluminum positive electrode lead 25 a was connected to the positive electrode 25, and the other end was connected to the lower surface of the sealing plate 22. One end of a nickel negative electrode lead 26 a was connected to the negative electrode 26, and the other end was connected to the inner bottom surface of the battery case 21. Thereafter, 5.5 g of a non-aqueous electrolyte was injected into the battery case 21, and the electrode group was impregnated with the non-aqueous electrolyte. Next, the sealing plate 22 was disposed in the opening of the battery case 21, and the opening end of the battery case 21 was caulked to the peripheral portion of the sealing plate 22 via the gasket 23. In this manner, a cylindrical nonaqueous electrolyte secondary battery (battery A) having a design capacity of 2150 mAh was produced.
　《実施例２》
　Ｔ１およびＴ２をそれぞれ１μｍおよび７０μｍとしたこと以外、実施例１と同様にして負極を作製し、電池Ｂを作製した。 Example 2
A negative electrode was produced in the same manner as in Example 1 except that T 1 and T 2 were 1 μm and 70 μm, respectively, and a battery B was produced.
　《実施例３》
　Ｔ１およびＴ２をそれぞれ５μｍおよび７０μｍとしたこと以外、実施例１と同様にして負極を作製し、電池Ｃを作製した。 Example 3
A negative electrode was produced in the same manner as in Example 1 except that T 1 and T 2 were 5 μm and 70 μm, respectively, and a battery C was produced.
　《実施例４》
　Ｔ１およびＴ２をそれぞれ３０μｍおよび５５μｍとし、負極長さ７１０ｍｍ、正極長さ６６０ｍｍとしたこと以外、実施例１と同様にして、電池Ｄを作製した。 Example 4
T 1 and T 2 was a 30μm and 55μm respectively, negative very long of 710 mm, except that the Seikyokucho of 660 mm, in the same manner as in Example 1, to prepare a battery D.
　《実施例５》
　Ｔ１およびＴ２をそれぞれ４０μｍおよび５０μｍとし、負極長さ７００ｍｍ、正極長さ６５０ｍｍとしたこと以外、実施例１と同様にして、電池Ｅを作製した。
　《実施例６》
　Ｔ１およびＴ２をそれぞれ４５μｍおよび５０μｍとし、負極長さ６９５ｍｍ、正極長さ６４５ｍｍとしたこと以外、実施例１と同様にして、電池Ｆを作製した。 Example 5
Battery E was produced in the same manner as in Example 1, except that T 1 and T 2 were 40 μm and 50 μm, respectively, the negative electrode length was 700 mm, and the positive electrode length was 650 mm.
Example 6
A battery F was produced in the same manner as in Example 1, except that T 1 and T 2 were 45 μm and 50 μm, respectively, the negative electrode length was 695 mm, and the positive electrode length was 645 mm.
　《実施例７》
　第１層の無機酸化物粒子として、チタン酸リチウムに代えてアルミナ（Ａｌ2Ｏ3、平均粒径０．３μｍ）を用いたこと以外、実施例２と同様にして負極を作製し、電池Ｇを作製した。 Example 7
A negative electrode was produced in the same manner as in Example 2 except that alumina (Al 2 O 3 , average particle size 0.3 μm) was used as the first layer of inorganic oxide particles instead of lithium titanate, and battery G Was made.
　《比較例１》
　Ｔ１およびＴ２をそれぞれ５０μｍおよび４０μｍとし、負極長さ６８０ｍｍ、正極長さ６３０ｍｍとしたこと以外、実施例１と同様にして、電池Ｈを作製した。 << Comparative Example 1 >>
A battery H was fabricated in the same manner as in Example 1, except that T 1 and T 2 were 50 μm and 40 μm, respectively, the negative electrode length was 680 mm, and the positive electrode length was 630 mm.
　《比較例２》
　第１層を形成せず、銅箔の表面に第２層を付着させたこと以外、実施例２と同様にして電池Ｉを作製した。 << Comparative Example 2 >>
A battery I was produced in the same manner as in Example 2 except that the first layer was not formed and the second layer was adhered to the surface of the copper foil.
（電池の評価方法）
　電池Ａ～Ｉに対して、次に示す釘刺し試験および充放電試験を行い、各電池の安全性および各電池の電池特性を評価した。 (Battery evaluation method)
The batteries A to I were subjected to the following nail penetration test and charge / discharge test to evaluate the safety of each battery and the battery characteristics of each battery.
　［釘刺し試験］
　電池Ａ～Ｉを以下の条件で充電した。そして、２０℃環境下で、直径２．７ｍｍの鉄釘を充電状態の電池の側面から５ｍｍ／秒の速度で２ｍｍの深さまで突き刺して、内部短絡を発生させた。釘刺し後３０秒が経過してから、釘刺し位置から離れた電池の側面に配置された熱電対で電池の表面温度を測定した。結果を表１に示す。 [Nail penetration test]
Batteries A to I were charged under the following conditions. Then, in an environment of 20 ° C., an iron nail having a diameter of 2.7 mm was pierced from the side surface of the charged battery to a depth of 2 mm at a speed of 5 mm / second to generate an internal short circuit. After 30 seconds from the nail penetration, the surface temperature of the battery was measured with a thermocouple placed on the side of the battery away from the nail penetration position. The results are shown in Table 1.
　－充電条件－
　定電流充電：電流値０．５Ｃ，充電終止電圧４．３Ｖ
　定電圧充電：電圧値４．３Ｖ，充電終止電流１００ｍＡ
［充放電試験］
　電池Ａ～Ｉに対して、２５℃環境下で以下の条件で３００サイクルの充放電を行った。初期放電容量（１サイクル目の放電容量）に対する３００サイクル目の放電容量の割合（％）を求め、容量維持率とした。結果を表１に示す。 -Charging conditions-
Constant current charging: Current value 0.5C, end-of-charge voltage 4.3V
Constant voltage charge: Voltage value 4.3V, charge end current 100mA
[Charge / discharge test]
The batteries A to I were charged and discharged for 300 cycles under the following conditions in a 25 ° C. environment. The ratio (%) of the discharge capacity at the 300th cycle to the initial discharge capacity (discharge capacity at the first cycle) was determined and used as the capacity maintenance rate. The results are shown in Table 1.
　－充放電条件－
　定電流充電：電流値１Ｃ，充電終止電圧４．２Ｖ
　定電圧充電：電圧値４．２Ｖ，充電終止電流１００ｍＡ
　定電流放電：電流値１Ｃ，放電終止電圧１．０Ｖ -Charging / discharging conditions-
Constant current charging: Current value 1C, end-of-charge voltage 4.2V
Constant voltage charging: Voltage value 4.2V, charging end current 100mA
Constant current discharge: current value 1C, final discharge voltage 1.0V
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　以下、得られた結果について詳述する。 Hereinafter, the results obtained will be described in detail.
　電池Ａ～Ｇは、釘刺し時の電池の表面温度が低く、高い容量維持率を示した。なかでも、電池ＡおよびＤ～Ｆは釘刺し時の電池の表面温度が特に低かった。これらの電池は第１層が十分な厚さを有するため、短絡時に第１層が高抵抗層として良好に機能したと考えられる。電池Ｅ～Ｇに比べると、電池Ａ～Ｄは特に高い容量維持率を示した。電池Ｅは第１層の厚さＴ１が４０μｍと比較的厚いため、容量維持率がやや低下したと考えられる。電池Ｆは第１層の厚さＴ１が４５μｍと厚いため、電池Ｅよりも容量維持率が低下したと考えられる。電池Ｇは無機酸化物粒子としてリチウムイオンを吸蔵および放出しない絶縁性酸化物であるアルミナを用いたため、容量維持率がやや低下したと考えられる。 Batteries A to G had a low battery surface temperature during nail penetration and exhibited a high capacity retention rate. In particular, the batteries A and D to F had particularly low battery surface temperatures during nail penetration. In these batteries, since the first layer has a sufficient thickness, it is considered that the first layer functioned well as a high resistance layer at the time of short circuit. Compared with the batteries E to G, the batteries A to D showed a particularly high capacity retention rate. Since the battery E is relatively thick, the thickness T 1 is 40μm of the first layer is believed that the capacity retention ratio was slightly reduced. Cell F is considered as the thickness T 1 of the first layer is thicker and 45 [mu] m, the capacity retention ratio was lower than the battery E. Since battery G used alumina, which is an insulating oxide that does not occlude and release lithium ions, as an inorganic oxide particle, it is considered that the capacity retention rate was slightly lowered.
　比較例である電池Ｈは、容量維持率の低下が著しく、得られる電池容量も小さかった。電池Ｈは第１層の厚さＴ１が第２層の厚さＴ２より大きいため、第１層が過剰な抵抗となり、充放電特性およびエネルギー密度が低下したと考えられる。電池Ｉは第１層を有さないため、釘刺し時の内部短絡および電池温度の過度の上昇を抑制することができなかった。 Battery H, which is a comparative example, had a significant decrease in capacity maintenance rate and a small battery capacity. Battery H Since the thickness T 1 of the first layer is larger than the thickness T 2 of the second layer, the first layer becomes excessive resistance, charge and discharge characteristics and the energy density is believed to have decreased. Since the battery I does not have the first layer, an internal short circuit at the time of nail penetration and an excessive increase in the battery temperature could not be suppressed.
　本発明によれば、優れた充放電特性と安全性とを両立した非水電解質二次電池を提供できる。よって、本発明に係る非水電解質二次電池は、携帯電子機器等の小型電源だけでなくＥＶ（Electric Vehicle）などの大型電源へも展開できる技術として有用である。 According to the present invention, it is possible to provide a non-aqueous electrolyte secondary battery that has both excellent charge / discharge characteristics and safety. Therefore, the non-aqueous electrolyte secondary battery according to the present invention is useful as a technology that can be developed not only for small power sources such as portable electronic devices but also for large power sources such as EVs (Electric Vehicles).
　本発明を現時点での好ましい実施態様に関して説明したが、そのような開示を限定的に解釈してはならない。種々の変形および改変は、上記開示を読むことによって本発明に属する技術分野における当業者には間違いなく明らかになるであろう。したがって、添付の請求の範囲は、本発明の真の精神および範囲から逸脱することなく、すべての変形および改変を包含する、と解釈されるべきものである。 Although the present invention has been described in terms of the presently preferred embodiments, such disclosure should not be construed as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains after reading the above disclosure. Accordingly, the appended claims should be construed to include all variations and modifications without departing from the true spirit and scope of this invention.
　１０　　　負極
　１１　　　集電体
　１２　　　第１層
　１３　　　第２層
　２１　　　電池ケース
　２２　　　封口板
　２３　　　ガスケット
　２５　　　正極
　２５ａ　　正極リード
　２６　　　負極
　２６ａ　　負極リード
　２７　　　セパレータ
　２８ａ　　上部絶縁板
　２８ｂ　　下部絶縁板
  DESCRIPTION OF SYMBOLS 10 Negative electrode 11 Current collector 12 1st layer 13 2nd layer 21 Battery case 22 Sealing plate 23 Gasket 25 Positive electrode 25a Positive electrode lead 26 Negative electrode 26a Negative electrode lead 27 Separator 28a Upper insulating plate 28b Lower insulating plate

Claims (7)

  1. 　集電体、前記集電体の表面に付着した第１層および前記第１層の表面に付着した第２層を備え、
    　前記第１層が、無機酸化物粒子および第１結着剤を含み、
    　前記第２層が、リチウムイオンを可逆的に吸蔵および放出可能な炭素材料および第２結着剤を含み、
    　前記第１層の厚さＴ1と、前記第２層の厚さＴ2とが、Ｔ1＜Ｔ2を満たす、非水電解質二次電池用負極。     A current collector, a first layer attached to the surface of the current collector, and a second layer attached to the surface of the first layer;
    The first layer includes inorganic oxide particles and a first binder,
    The second layer includes a carbon material capable of reversibly occluding and releasing lithium ions and a second binder,
    Wherein the thickness T 1 of the first layer, wherein the thickness T 2 of the second layer, T 1 <satisfy T 2, the non-aqueous electrolyte negative electrode for a secondary battery.
  2. 　前記無機酸化物粒子が、スピネル型の結晶構造を有するチタン酸リチウムを含む、請求項１記載の非水電解質二次電池用負極。 The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the inorganic oxide particles include lithium titanate having a spinel crystal structure.
  3. 　前記Ｔ1と前記Ｔ2との比Ｔ1／Ｔ2が、０．１５以上、０．８以下である、請求項１または２記載の非水電解質二次電池用負極。 The ratio T 1 / T 2 of the T 1 and the T 2 is 0.15 or more and 0.8 or less, according to claim 1 or 2, negative electrode for a non-aqueous electrolyte secondary battery according.
  4. 　前記Ｔ1が１～４０μｍである、請求項１～３のいずれか１項に記載の非水電解質二次電池用負極。 The negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the T 1 is 1 to 40 µm.
  5. 　前記第１層に含まれる前記第１結着剤の量Ｗ1が、前記無機酸化物粒子１００質量部あたり０．５～１０質量部である、請求項１～４のいずれか１項に記載の非水電解質二次電池用負極。 The amount W 1 of the first binder contained in the first layer is 0.5 to 10 parts by mass per 100 parts by mass of the inorganic oxide particles. Negative electrode for non-aqueous electrolyte secondary battery.
  6. 　前記第１層が、更に、前記無機酸化物粒子１００質量部あたり１～５質量部の導電材を含む、請求項１～５のいずれか１項に記載の非水電解質二次電池用負極。 6. The negative electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the first layer further contains 1 to 5 parts by mass of a conductive material per 100 parts by mass of the inorganic oxide particles.
  7. 　正極、負極および前記正極と前記負極との間に介在するセパレータおよび非水電解質を含み、前記負極が、請求項１～６のいずれか１項に記載の非水電解質二次電池用負極である、非水電解質二次電池。
          The negative electrode for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 6, comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. , Non-aqueous electrolyte secondary battery.
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