Non-aqueous electrolyte battery and battery pack

Abstract

According to one embodiment, provided is a non-aqueous electrolyte battery that includes a positive electrode containing a lithium-containing nickel cobalt manganese oxide, a negative electrode containing a lithium-titanium-containing oxide, and a non-aqueous electrolyte. The ratio PLi−F / PNi of the peak intensity PLi−F of the maximum intensity peak appearing within the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the positive electrode surface of the positive electrode to the peak intensity PNi of the maximum intensity peak appearing within the range of 850 eV to 858 eV in the X-ray photoelectron spectrum of the positive electrode surface is 0.6-1. The ratio NLi−F / N Ti of the peak intensity NLi−F of the maximum intensity peak appearing within the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the negative electrode surface of the negative electrode to the peak intensity NTi of the maximum intensity peak appearing within the range of 454 eV to 460 eV in the X-ray photoelectron spectrum of the negative electrode surface is 1.8-3.

Description

Nonaqueous electrolyte battery and battery pack

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a non-aqueous electrolyte battery and a battery pack.

[0002] Secondary batteries, including lithium-ion secondary batteries, are widely used in mobile devices, vehicles such as automobiles, storage batteries, etc. Secondary batteries are power storage devices whose market size is expected to expand.

[0003] A secondary battery includes electrodes, including a positive electrode and a negative electrode. The secondary battery may further include an electrolyte. One design of a secondary battery electrode includes a current collector and an active material-containing layer disposed on a major surface of the current collector. The active material-containing layer of the electrode may be, for example, a layer composed of active material particles, a conductive agent, and a binder, and may be a porous body capable of retaining an electrolyte.

[0004] Lithium titanate is an example of an active material used in the negative electrode of a lithium-ion battery or secondary battery. Lithium-ion secondary batteries using lithium titanate in the negative electrode have excellent low-temperature input / output and life performance.

[0005] Japanese Patent Application Publication No. 2012-174350 International Publication No. 2016 / 129527

[0006] An object of the present invention is to provide a non-aqueous electrolyte battery having an excellent charge / discharge cycle life, and a battery pack including the battery.

[0007] According to an embodiment, there is provided a non-aqueous electrolyte battery including a positive electrode containing a lithium-containing nickel-cobalt-manganese oxide, a negative electrode including a negative electrode active material containing layer containing a lithium-titanium-containing oxide, and a non-aqueous electrolyte. The peak intensity P of the most intense peak appearing in the range of 850 eV to 858 eV in an X-ray photoelectron spectrum of the positive electrode surface of the positive electrode is Ni The peak intensity P of the most intense peak appearing in the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the positive electrode surface Li-F The ratio P Li-F / P Ni is 0.6 or more and 1 or less. The peak intensity N of the most intense peak appearing in the range of 454 eV to 460 eV in the X-ray photoelectron spectrum of the negative electrode surface TiThe peak intensity N of the most intense peak appearing in the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the negative electrode surface Li-F Ratio of N Li-F / N Ti is 1.8 or more and 3 or less.

[0008] According to another embodiment, a battery pack including the nonaqueous electrolyte battery according to the above embodiment is provided.

[0009] FIG. 1 is a partially cutaway perspective view showing an example of a battery according to an embodiment. FIG. 2 is an enlarged cross-sectional view of part A of the battery shown in FIG. 1. FIG. 3 is a partially cutaway perspective view showing another example of a battery according to an embodiment. FIG. 4 is an enlarged cross-sectional view of part B of the battery shown in FIG. 4. FIG. 5 is an exploded perspective view showing an example of a battery pack according to an embodiment. FIG. 6 is a block diagram showing an example of an electrical circuit of the battery pack shown in FIG. Embodiment

[0010] Lithium-ion secondary batteries using lithium titanate as the negative electrode have excellent low-temperature input / output and lifespan performance, but one issue they face is the large amount of gas generation.

[0011] As a countermeasure against gas generation, coating lithium titanate with polymeric materials has been investigated. However, such coating layers have low Li ion conductivity and act as a resistive component. As a result, the properties of lithium titanate cannot be fully utilized.

[0012] As an alternative, active materials with layered structures can be added. Among these active materials, lithium-containing cobalt oxide acts as a gas adsorbent, so using lithium-containing cobalt oxide as a positive electrode active material reduces gas generation. However, lithium-containing cobalt oxide has the problem of significant degradation at high potentials. Therefore, the use of lithium-containing nickel-cobalt-manganese oxide as an alternative to lithium-containing cobalt oxide is being considered.

[0013] Hereinafter, embodiments will be described with reference to the drawings. Note that common components throughout the embodiments are designated by the same reference numerals, and redundant explanations will be omitted. Each figure is a schematic diagram intended to facilitate explanation and understanding of the embodiments, and while the shapes, dimensions, ratios, etc. may differ in some places from the actual device, these can be appropriately modified in design, taking into consideration the following explanation and known techniques.

[0014] First Embodiment According to a first embodiment, a non-aqueous electrolyte battery is provided, which includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a lithium-containing nickel-cobalt-manganese oxide as a first positive electrode active material. In a spectrum obtained by analyzing the positive electrode surface by X-ray photoelectron spectroscopy (XPS), the peak intensity P of the most intense peak appearing in the range of 850 eV to 858 eV is Ni The peak intensity P of the most intense peak appearing in the range from 682 eV to 685 eV Li-F The ratio P Li-F / P Ni is 0.6 or more and 1 or less. The negative electrode contains a lithium-titanium-containing oxide. In a spectrum obtained by XPS analysis of the negative electrode surface, the peak intensity N Ti The peak intensity N of the most intense peak appearing in the range from 682 eV to 685 eV Li-F Ratio of N Li-F / N Ti is between 1.8 and 3.

[0015] In the XPS spectrum obtained by XPS analysis of the positive electrode surface, the most intense peak appearing in the range of 682 eV to 685 eV is attributed to the Li-F bond among the F1s component derived from fluorine present on the positive electrode surface, while the most intense peak appearing in the range of 850 eV to 858 eV is attributed to the Ni2p3 component derived from nickel present on the positive electrode surface.

[0016] In the XPS spectrum obtained by XPS analysis of the anode surface, the most intense peak appearing in the range of 682 eV to 685 eV is attributed to the Li-F bond among the F1s components derived from fluorine present on the anode surface, while the most intense peak appearing in the range of 454 eV to 460 eV is attributed to the Ti2P3 component derived from titanium present on the anode surface.

[0017] The positive electrode and negative electrode contained in such a nonaqueous electrolyte each have a fluorine-containing coating on the electrode surface. The positive electrode may include, for example, a positive electrode active material-containing layer containing lithium-containing nickel-cobalt-manganese oxide as the positive electrode active material, and the fluorine-containing coating may coat the positive electrode active material-containing layer. Similarly, the negative electrode may include, for example, a negative electrode active material-containing layer containing lithium-titanium-containing oxide as the negative electrode active material, and the fluorine-containing coating may coat the negative electrode active material-containing layer. Gas generation due to the decomposition reaction of the nonaqueous electrolyte occurs in both the positive electrode and the negative electrode. The fluorine-containing coating suppresses the decomposition reaction of the nonaqueous electrolyte on the positive electrode surface and the negative electrode surface, respectively, thereby reducing gas generation at each electrode. While suppressing side reactions that lead to gas generation, the fluorine-containing coating has Li ion conductivity. Therefore, the provision of the coating results in little change in internal resistance, and the input / output performance of the battery is not significantly impaired. Each fluorine-containing coating may contain, for example, lithium fluoride.

[0018] The peak intensity P of the most intense peak in the range from 682 eV to 685 eV in the XPS spectrum of the positive electrode surface Li-F represents the proportion of the fluorine-containing coating (hereinafter, sometimes referred to as the positive electrode coating) covering the surface of the positive electrode active material-containing layer. The peak intensity P Ni represents the proportion of the lithium-containing nickel-cobalt-manganese oxide present on the surface of the positive electrode, which is contained as an active material in the positive electrode. Li-F / P Ni indicates the degree of coverage by the positive electrode film. Similarly, the peak intensity N of the most intense peak in the range of 682 eV to 685 eV in the XPS spectrum of the negative electrode surface Li-Frepresents the proportion of the fluorine-containing coating (hereinafter, sometimes referred to as the negative electrode coating) covering the surface of the negative electrode active material-containing layer, and the peak intensity N of the most intense peak in the range from 454 eV to 460 eV Ti represents the proportion of the lithium-titanium-containing oxide contained as an active material on the surface of the negative electrode. Li-F / N Ti indicates the degree of coverage by the negative electrode film.

[0019] In such a non-aqueous electrolyte battery, the ratio P Li-F / P Ni is 0.6 or more and 1 or less, and the ratio N Li-F / N Ti is 1.8 or more and 3 or less. That is, the degree of coverage of the negative electrode by the negative electrode coating is greater than the degree of coverage of the positive electrode by the positive electrode coating. As described above, gas is generated by the side reaction between the positive electrode active material and the non-aqueous electrolyte and the side reaction between the negative electrode active material and the non-aqueous electrolyte. The gas generated at the negative electrode includes carbon monoxide (CO) gas generated by the reduction reaction of the non-aqueous electrolyte. CO generated at the negative electrode is oxidized at the positive electrode to carbon dioxide (CO ２ ) and can dissolve in the nonaqueous electrolyte. In a nonaqueous electrolyte battery in which the ratios of the coating components on the positive and negative electrodes are as described above, the coating on the negative electrode suppresses gas generation at the negative electrode, while keeping the coating on the positive electrode relatively thin allows the positive electrode to exhibit CO oxidation ability. This nonaqueous electrolyte battery has a good balance of gas generation between the positive and negative electrodes.

[0020] Peak intensity N Ti Peak intensity P Ni The ratio P Ni / N Ti It is preferable that the peak intensity P Ni and N Ti and P each represent the proportion of the surface of the active material-containing layer that is not covered with the fluorine-containing coating and can be in direct contact with the non-aqueous electrolyte. Ni / N Ti In a battery in which the ratio of CO2 to CO2 is within the above range, the reduction reaction at the negative electrode that generates CO2 and the CO2 are converted to CO2. ２This balances the oxidation reaction at the positive electrode, which oxidizes the metal to the metal.

[0021] The amount of the anode coating on the anode surface can be estimated by time-of-flight secondary ion mass spectrometry (TOF-SIMS). In the TOF-SIMS spectrum, the peak at m / z=165 may be derived from a component contained in the anode coating. For example, as described below, a cathode coating and an anode coating can be formed by aging a battery in a state where an additive such as lithium difluorobisoxalate phosphate (LiDFBOP) is contained in the electrolyte, and the peak at m / z=165 may be a detection peak of an anion derived from LiDFBOP. In the TOF-SIMS spectrum, the peak at m / z=16 may be a detection peak of an oxygen anion (O － ) is the detected peak. The oxygen anions detected in TOF-SIMS analysis of the anode surface can be derived from oxides such as lithium-containing titanium oxides as active materials or from oxygen contained in the anode coating. The negative ion count NI of m / z=165 165 and m / z=16 negative ion count NI 16 and 0.12 < NI 165 / NI 16 It is preferable that the relationship of ≈0.18 is satisfied. In a negative electrode that satisfies this relationship, the amount of the negative electrode coating is appropriate from the viewpoints of suppressing gas generation and input / output performance.

[0022] Batteries according to embodiments will be described in detail below. Such nonaqueous electrolyte batteries may include an electrode assembly. The electrode assembly may include a positive electrode, a negative electrode, and a separator positioned between the positive electrode and the negative electrode. The positive electrode may include a positive electrode current collector tab electrically connected to the electrode assembly. The negative electrode may include a negative electrode current collector tab electrically connected to the electrode assembly.

[0023] The nonaqueous electrolyte battery may further include a housing member. The electrode group may be housed in the housing member. The housing member may house a nonaqueous electrolyte. The nonaqueous electrolyte may be impregnated into the electrode group housed in the housing member.

[0024] Such a nonaqueous electrolyte battery may further include a positive electrode terminal and a negative electrode terminal. A portion of the positive electrode terminal is electrically connected to a portion of the positive electrode, thereby serving as a conductor for electron transfer between the positive electrode and an external terminal. The positive electrode terminal may be connected, for example, to a positive electrode current collector, particularly a positive electrode current collector tab. Similarly, a portion of the negative electrode terminal is electrically connected to a portion of the negative electrode, thereby serving as a conductor for electron transfer between the negative electrode and an external terminal. The negative electrode terminal may be connected, for example, to a negative electrode current collector, particularly a negative electrode current collector tab.

[0025] Such a non-aqueous electrolyte battery may be, for example, a secondary battery, and the secondary battery may include, for example, a lithium ion secondary battery that contains lithium ions as charge carriers.

[0026] (1) Positive Electrode The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer carried on one or both surfaces of the positive electrode current collector.

[0027] The positive electrode active material containing layer contains lithium-containing nickel cobalt manganese oxide as a first positive electrode active material. The lithium-containing nickel cobalt manganese oxide is, for example, LiNi 1-y-z Co y Mn z O2, where the ranges of each subscript are 0<y<1, 0<z<1, and 0<y+z<1.

[0028] The positive electrode active material may contain, in addition to the first positive electrode active material, another compound as a second positive electrode active material. The second positive electrode active material may contain, for example, one or more compounds selected from the group consisting of lithium-containing manganese oxide, lithium-containing cobalt oxide, manganese dioxide, lithium-manganese composite oxide, lithium-containing nickel oxide, lithium-containing nickel-cobalt composite oxide, lithium-containing manganese-cobalt oxide, lithium-containing iron oxide, vanadium oxide containing lithium, and chalcogen compounds such as titanium disulfide and molybdenum disulfide.

[0029] The lithium-containing manganese oxide is, for example, Li w Spinel-type lithium manganese oxide represented by Mn2O4 and Li wThe subscript w is 0.9 or more and 1.2 or less. Other examples of lithium-containing manganese oxides include those with the chemical formula LiMn 2-x M x Spinel-type lithium manganese oxide, which is a composite oxide represented by the formula O4, is an example. Here, M is at least one element selected from the group consisting of Mg, Ti, Cr, Fe, Co, Zn, Al, and Ga. The subscript x is 0.22 or more and 0.7 or less.

[0030] Examples of lithium-containing cobalt oxides include Li w CoO2. The chemical formula is Li w The range of the subscript w in CoO2 is 0<w≦1. An example of a lithium-containing nickel oxide is Li w NiO2 (0.9≦w≦1.2). Examples of lithium-containing nickel-cobalt composite oxides include LiNi 1-y Co y O2 (where 0<y<1). An example of a lithium-containing manganese cobalt oxide is LiMn ｙ Co 1-ｙ O2 (where 0<y<1).

[0031] Of the positive electrode active materials in the positive electrode active material-containing layer, the first positive electrode active material (lithium-containing nickel-cobalt-manganese oxide) preferably accounts for 50% by mass or more and 100% by mass or less, and more preferably 70% by mass or more and 100% by mass or less.

[0032] The positive electrode active material is, for example, in a particulate form. When in a particulate form, the positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles.

[0033] The average particle size of the particles of the first positive electrode active material is preferably 0.05 μm or more and 30 μm or less.

[0034] The positive electrode active material-containing layer may contain a binder and a conductive agent, if necessary.

[0035] The binder can bind the active material and the conductive agent. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber. The type of binder used can be one or more types.

[0036] The conductive agent can increase electronic conductivity and reduce contact resistance with the current collector. Examples of the conductive agent include carbon materials such as acetylene black, carbon black, graphite, carbon nanofibers, and carbon nanotubes. The type of conductive agent used can be one or more types.

[0037] The compounding ratio of the positive electrode active material, conductive agent, and binder is preferably in the range of 80% by mass or more and 95% by mass or less of the positive electrode active material, 3% by mass or more and 18% by mass or less of the conductive agent, and 2% by mass or more and 7% by mass or less of the binder.

[0038] The current collector may be, for example, a sheet containing a highly electrically conductive material. For example, aluminum foil or aluminum alloy foil may be used as the current collector. When aluminum foil or aluminum alloy foil is used, its thickness is preferably 20 μm or less. The aluminum alloy foil may contain magnesium (Mg), titanium (Ti), zinc (Zn), manganese (Mn), silicon (Si), etc. The aluminum alloy foil may also contain other transition metals. The content of the transition metal in the aluminum alloy foil is preferably 1 mass% or less. Examples of transition metals include iron (Fe), copper (Cu), nickel (Ni), and chromium (Cr). The current collector is preferably aluminum foil or an aluminum alloy foil containing aluminum and one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0039] The current collector may include a portion on its surface that does not carry an active material-containing layer. This portion may function, for example, as a positive electrode current collecting tab. Alternatively, the positive electrode may further include a positive electrode current collecting tab that is separate from the positive electrode current collector. The separate positive electrode current collecting tab may be electrically connected to the positive electrode.

[0040] The density of the positive electrode active material-containing layer is 2.5 g / cm ３ 3.1g / cm or more ３ It is preferable to do the following:

[0041] The basis weight of the positive electrode active material-containing layer, i.e., the weight per unit area (g / m ２ ) is 30 g / m ２ 130g / m or more ２ It can be the following:

[0042] In manufacturing a positive electrode, for example, a positive electrode active material, a positive electrode conductive agent, and a binder are first suspended in an appropriate solvent, and the resulting slurry is applied to a positive electrode current collector and dried to form a positive electrode active material-containing layer, followed by pressing. Alternatively, the positive electrode active material, the positive electrode conductive agent, and the binder may be formed into pellets to be used as the positive electrode active material-containing layer.

[0043] (2) Negative Electrode The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer supported on one or both surfaces of the negative electrode current collector. The negative electrode active material-containing layer contains at least a lithium-titanium-containing oxide as a negative electrode active material.

[0044] The negative electrode current collector may include a portion that does not support a negative electrode active material-containing layer on its surface. This portion may function as a negative electrode current collecting tab. Alternatively, the negative electrode may include a negative electrode current collecting tab that is separate from the negative electrode current collector.

[0045] The lithium titanium-containing oxide includes, for example, lithium titanium oxide, lithium titanium composite oxide in which some of the constituent elements of lithium titanium oxide are substituted with different elements, orthorhombic lithium titanium-containing oxide, and monoclinic lithium niobium titanium-containing oxide. The lithium titanium oxide includes, for example, lithium titanate having a spinel structure (e.g., Li ４＋ｘ Ti ５ O １２ (x is a value that changes with charge and discharge, 0≦x≦3)), ramsdellite-type lithium titanate (e.g., Li ２＋ｙ Ti ３ O ７ (where y is a value that changes with charge and discharge, 0≦y≦3)). On the other hand, the molar ratio of oxygen is ４＋ｘTi ５ O １２ So, 12, Ramsdellite-type Li ２＋ｙ Ti ３ O ７ However, these values ​​may vary depending on the influence of oxygen nonstoichiometry, etc. The type of negative electrode active material may be one or more types.

[0046] The orthorhombic lithium titanium-containing oxide includes those having the general formula Li ２＋ｗ Na ２－ｘ M1 ｙ Ti ６－ｚ M2 ｚ O １４＋δ wherein M1 is Cs and / or K, M2 is a compound containing at least one of Zr, Sn, V, Nb, Ta, Mo, W, Fe, Co, Mn, and Al, and 0≦w≦4, 0≦x≦2, 0≦y≦2, 0≦z<6, and −0.5≦δ≦0.5.

[0047] The monoclinic lithium niobium titanium-containing oxide includes those having the general formula Li ｘ Ti １－ｙ M3 ｙ Nb ２－ｚ M4 ｚ O ７＋δ wherein M3 is at least one selected from the group consisting of Zr, Si, Sn, Fe, Co, Mn, and Ni, and M4 is at least one selected from the group consisting of V, Nb, Ta, Mo, W, and Bi, and 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

[0048] The lithium-titanium-containing oxide is, for example, in the form of particles. When in the form of particles, the lithium-titanium-containing oxide may be primary particles or secondary particles formed by agglomeration of the primary particles.

[0049] The negative electrode active material in the negative electrode active material-containing layer preferably contains lithium titanium-containing oxide in an amount of 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less. ４＋ｘ Ti ５ O １２0≦x≦3) in an amount of 50% by mass or more and 100% by mass or less. Even more preferably, the negative electrode active material contains 70% by mass or more and 100% by mass or less of lithium titanate having a spinel structure.

[0050] The negative electrode active material-containing layer may contain a conductive agent and a binder, if necessary.

[0051] Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide, polyamide, etc. One or more types of binder may be used.

[0052] Examples of the negative electrode conductive agent include carbon black such as acetylene black and ketjen black, graphite, carbon fiber, carbon nanotubes, fullerene, etc. The type of conductive agent may be one or more types.

[0053] The blending ratios of the negative electrode active material, conductive agent, and binder in the negative electrode active material-containing layer are preferably 70% by mass or more and 96% by mass or less of the negative electrode active material, 2% by mass or more and 28% by mass or less of the conductive agent, and 2% by mass or more and 28% by mass or less of the binder.

[0054] The density of the negative electrode active material-containing layer is 2.0 g / cm ３ It is preferable to set it to more than this.

[0055] The average particle diameter of the particles contained in the negative electrode active material-containing layer is preferably 0.3 μm or more and 1.5 μm or less. Gas generation from the negative electrode increases in proportion to the specific surface area of ​​the lithium-titanium-containing oxide contained as the negative electrode active material. By using a lithium-titanium-containing oxide having an appropriate particle diameter as the negative electrode active material, a high-output battery can be obtained while further suppressing gas generation. The average particle diameter of the particles in the negative electrode active material-containing layer is, for example, the particle diameter (D) at which the volume-based cumulative frequency from the small particle diameter side of the cumulative frequency distribution becomes 50% in the particle size distribution of the negative electrode active material obtained by laser diffraction scattering method. ５０ )

[0056] The current collector is preferably an aluminum foil or an aluminum alloy foil. When an aluminum foil or an aluminum alloy foil is used, its thickness is preferably 20 μm or less. The aluminum alloy foil may contain magnesium (Mg), titanium (Ti), zinc (Zn), manganese (Mn), silicon (Si), etc. The aluminum alloy foil may also contain other transition metals. The content of the transition metal in the aluminum alloy foil is preferably 1 mass% or less. Examples of transition metals include iron (Fe), copper (Cu), nickel (Ni), and chromium (Cr). The current collector is preferably an aluminum foil or an aluminum alloy foil containing aluminum and one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0057] The negative electrode is fabricated, for example, by suspending a negative electrode active material, a negative electrode conductive agent, and a binder in a suitable solvent, applying the resulting slurry to a negative electrode current collector, drying the slurry, and then pressing the resulting slurry to form a negative electrode active material-containing layer. Alternatively, the negative electrode active material, the negative electrode conductive agent, and the binder may be formed into pellets and used as the negative electrode active material-containing layer.

[0058] The basis weight of the negative electrode active material-containing layer, i.e., the mass per unit area (g / m ２ ) is 10 g / m ２ 80g / m or more ２ It can be the following:

[0059] (3) Nonaqueous Electrolyte Examples of the nonaqueous electrolyte include a liquid nonaqueous electrolyte prepared by dissolving an electrolyte salt in a nonaqueous solvent, and a gel nonaqueous electrolyte obtained by combining a liquid nonaqueous electrolyte with a polymer material.

[0060] The electrolyte salt may be, for example, lithium perchlorate (LiClO ４ ), lithium hexafluorophosphate (LiPF ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium arsenic hexafluoride (LiAsF ６ ), lithium trifluoromethanesulfonate (LiCF ３ SO ３), lithium bistrifluoromethylsulfonylimide (LiN(CF) ３ SO ２ ) ２ ), and lithium aluminum tetrafluoride (LiAlF ４ These electrolytes may be used alone or in combination of two or more. The electrolyte salt preferably contains lithium hexafluorophosphate.

[0061] The electrolyte salt is preferably dissolved in the non-aqueous solvent in a range of 0.5 mol / L to 2.5 mol / L.

[0062] Examples of non-aqueous solvents include organic solvents such as cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC); chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); cyclic ethers such as tetrahydrofuran (THF) and 2-methyltetrahydrofuran (2MeTHF); chain ethers such as dimethoxyethane (DME); cyclic esters such as γ-butyrolactone (BL); chain esters such as methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; acetonitrile (AN); and sulfolane (SL). These organic solvents can be used alone or in the form of a mixture of two or more.

[0063] Examples of polymer materials used for the gel non-aqueous electrolyte include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

[0064] (4) Separator The material of the separator is not particularly limited. It is desirable that the separator have electrical insulation properties. For example, a porous film, a microporous film, a woven fabric, a nonwoven fabric, or a laminate of the same or different materials among these can be used as the separator. Examples of materials that can be used to form the separator include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, polyolefin, cellulose, polyethylene terephthalate, and polymers such as vinylon. The separator may be made of one type of material, or two or more types may be used in combination.

[0065] The thickness of the separator is preferably 2 μm or more and 30 μm or less.

[0066] (5) Electrode Group In the electrode group, the positive electrode active material-containing layer and the negative electrode active material-containing layer can face each other, for example, via a separator. The electrode group can have various structures. For example, the electrode group can have a stacked structure. An electrode group with a stacked structure can be obtained, for example, by alternately stacking multiple positive electrodes and multiple negative electrodes with a separator sandwiched between the positive electrode active material-containing layer and the negative electrode active material-containing layer. Alternatively, the electrode group can have a wound structure. A wound electrode group can be obtained, for example, by stacking one separator, one negative electrode, another separator, and one positive electrode in this order to form a laminate, and then winding this laminate. Alternatively, instead of using multiple separators, a single separator may be used in a folded state. For example, a single separator may be used in a zigzag pattern.

[0067] (6) Exterior Member The exterior member accommodates the electrode group and the non-aqueous electrolyte. The electrode group may be impregnated with the non-aqueous electrolyte within the exterior member. A portion of each of the positive electrode terminal and the negative electrode terminal may extend from the exterior member.

[0068] The exterior member may be formed from a laminate film or may be a metal container. When a metal container is used, the lid may be integral with the container or may be a separate member. The thickness of the metal container is preferably 0.5 mm or less, more preferably 0.2 mm or less. The shape of the exterior member may be flat, rectangular, cylindrical, coin-shaped, button-shaped, sheet-shaped, laminated, or the like. In addition to small batteries installed in portable electronic devices, large batteries installed in two- or four-wheeled automobiles may also be used.

[0069] The thickness of the laminate film exterior component is preferably 0.2 mm or less. Examples of laminate films include multilayer films containing a resin film and a metal layer disposed between the resin films. The metal layer is preferably aluminum foil or aluminum alloy foil for weight reduction. Polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used for the resin film. The laminate film can be sealed by heat fusion to form it into the shape of the exterior component.

[0070] The metal container is made of aluminum or an aluminum alloy. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. In aluminum or an aluminum alloy, the content of transition metals such as iron, copper, nickel, and chromium is preferably 100 ppm or less, in order to significantly improve long-term reliability and heat dissipation in a high-temperature environment.

[0071] The metal container made of aluminum or an aluminum alloy desirably has an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. By setting the average crystal grain size to 50 μm or less, the strength of the metal container made of aluminum or an aluminum alloy can be dramatically increased, allowing the container to be made even thinner. As a result, a nonaqueous electrolyte battery that is lightweight, has high output, and has excellent long-term reliability, making it suitable for use in vehicles, etc., can be realized.

[0072] Next, specific examples of the nonaqueous electrolyte battery according to the embodiment will be described with reference to the drawings.

[0073] First, an example of a nonaqueous electrolyte battery will be described with reference to FIGS. 1 and 2. FIG.

[0074] 1 is a partially cutaway perspective view of an example of a nonaqueous electrolyte battery according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a portion A of the nonaqueous electrolyte battery shown in FIG.

[0075] 1 and 2 includes a flat electrode group 1 and an exterior member 7 made of a laminate film. The flat electrode group 1 includes a negative electrode 2, a positive electrode 3, and a separator 4. The flat electrode group 1 is formed by winding the negative electrode 2 and the positive electrode 3 together in a flat shape with the separator 4 interposed between them.

[0076] As shown in Fig. 2, the negative electrode 2 includes a negative electrode current collector 2a and a negative electrode active material-containing layer 2b supported on the negative electrode current collector 2a. As shown in Fig. 2, in the outermost portion of the negative electrode 2, the negative electrode active material-containing layer 2b is not supported on one of the two main surfaces of the negative electrode current collector 2a that does not face the positive electrode 3. In other portions of the negative electrode 2, the negative electrode active material-containing layer 2b is supported on both main surfaces of the negative electrode current collector. As shown in Fig. 2, the positive electrode 3 includes a positive electrode current collector 3a and a positive electrode active material-containing layer 3b supported on the two main surfaces of the positive electrode current collector 3a.

[0077] A strip-shaped negative electrode terminal 5 is electrically connected to the negative electrode 2. A strip-shaped positive electrode terminal 6 is electrically connected to the positive electrode 3.

[0078] The electrode group 1 is housed in a laminate film exterior member 7 with the ends of the negative electrode terminal 5 and the positive electrode terminal 6 extending from the exterior member 7. A non-aqueous electrolyte (not shown) is housed in the laminate film exterior member 7. The electrode group 1 is impregnated with the non-aqueous electrolyte. The laminate film exterior member 7 has one end sandwiching the negative electrode terminal 5 and the positive electrode terminal 6, and is sealed by heat-sealing this end and two other ends perpendicular to this end.

[0079] Next, another example of the battery according to the embodiment will be described in detail with reference to Fig. 3. Fig. 3 is a partially cutaway perspective view showing another example of the battery according to the embodiment.

[0080] The battery 100 shown in FIG. 3 differs from the battery 100 shown in FIGS. 1 and 2 in that the exterior member is composed of a metal container 17a and a sealing plate 17b.

[0081] The flat electrode group 1 includes a negative electrode, a positive electrode, and a separator, similar to the electrode group 1 in the battery 100 shown in Figures 1 and 2. The electrode group 1 has a similar structure between Figures 1 and 3. However, in Figure 3, as will be described later, a negative electrode lead 15a and a positive electrode lead 16a are electrically connected to the negative electrode and the positive electrode, respectively, instead of the negative electrode terminal 5 and the positive electrode terminal 6.

[0082] In the battery 100 shown in Fig. 3, such an electrode group 1 is housed in a metal container 17a. The metal container 17a further houses an electrolyte (not shown). The metal container 17a is sealed with a metal sealing plate 17b. The metal container 17a and the sealing plate 17b constitute, for example, an exterior can as an exterior member.

[0083] One end of the negative electrode lead 15a is electrically connected to the negative electrode current collector, and the other end is electrically connected to the negative electrode terminal 15. One end of the positive electrode lead 16a is electrically connected to the positive electrode current collector, and the other end is electrically connected to a positive electrode terminal 16 fixed to the sealing plate 17b. The positive electrode terminal 16 is fixed to the sealing plate 17b via an insulating member 17c. The positive electrode terminal 16 and the sealing plate 17b are electrically insulated by the insulating member 17c.

[0084] 4 and 5 show a battery including a stacked electrode group as yet another example of a battery. Fig. 4 is a partially cutaway perspective view showing yet another example of a battery according to an embodiment. Fig. 5 is an enlarged cross-sectional view of part B of the battery shown in Fig. 4.

[0085] The battery 100 of the example shown in FIGS. 4 and 5 includes the electrode group 1 shown in FIGS. 4 and 5, the exterior member 7 shown in FIGS. 4 and 5, the positive electrode terminal 6 shown in FIGS. 4 and 5, and the negative electrode terminal 5 shown in FIG. 4.

[0086] The electrode group 1 shown in FIGS. 4 and 5 includes a plurality of positive electrodes 3, a plurality of negative electrodes 2, and one separator 4.

[0087] As shown in Fig. 5, each positive electrode 3 includes a positive electrode current collector 3a and a positive electrode active material-containing layer 3b formed on both sides of the positive electrode current collector 3a. Also, as shown in Fig. 5, the positive electrode current collector 3a includes a portion on its surface where the positive electrode active material-containing layer 3b is not formed. This portion functions as a positive electrode current collecting tab 3c.

[0088] Each negative electrode 2 includes a negative electrode current collector 2a and a negative electrode active material-containing layer 2b formed on both sides of the negative electrode current collector 2a. The negative electrode current collector 2a also includes a portion (not shown) on its surface where the negative electrode active material-containing layer 2b is not formed. This portion functions as a negative electrode current collecting tab.

[0089] As shown in part in Fig. 5, the separator 4 is zigzag folded. A positive electrode 3 or a negative electrode 2 is disposed in the space defined by the opposing surfaces of the zigzag folded separator 4. As a result, the positive electrode 3 and the negative electrode 2 are stacked such that the positive electrode active material-containing layer 3b and the negative electrode active material-containing layer 2b face each other with the separator 4 interposed therebetween, as shown in Fig. 5. In this manner, an electrode group 1 is formed.

[0090] As shown in Fig. 5, the positive electrode current collector tabs 3c of the electrode group 1 extend beyond the respective ends of the positive electrode active material-containing layer 3b and the negative electrode active material-containing layer 2b. As shown in Fig. 5, these positive electrode current collector tabs 3c are joined together and connected to a positive electrode terminal 6. Although not shown, the negative electrode current collector tabs of the electrode group 1 also extend beyond the other end of the positive electrode active material-containing layer 3b and the negative electrode active material-containing layer 2b. Although not shown, these negative electrode current collector tabs are joined together and connected to a negative electrode terminal 5 shown in Fig. 4.

[0091] As shown in FIGS. 4 and 5, the electrode group 1 is housed in an exterior member 7 made of an exterior container made of a laminate film.

[0092] The exterior member 7 is formed from an aluminum-containing laminate film consisting of aluminum foil 71 and resin films 72 and 73 formed on both sides of the aluminum foil 71. The aluminum-containing laminate film forming the exterior member 7 is folded at a folding portion 7d so that the resin film 72 faces inward, thereby housing the electrode group 1. As shown in FIGS. 4 and 5 , at the peripheral portion 7b of the exterior member 7, the facing portions of the resin film 72 sandwich the positive electrode terminal 6 therebetween. Similarly, at the peripheral portion 7c of the exterior member 7, the facing portions of the resin film 72 sandwich the negative electrode terminal 5 therebetween. The positive electrode terminal 6 and the negative electrode terminal 5 extend in opposite directions from the exterior member 7.

[0093] At the peripheral portions 7 a , 7 b and 7 c of the exterior member 7 , excluding the portions sandwiching the positive electrode terminal 6 and the negative electrode terminal 5 , the opposing portions of the resin film 72 are heat-sealed.

[0094] In addition, in the battery 100, in order to improve the bonding strength between the positive electrode terminal 6 and the resin film 72, an insulating film 9 is provided between the positive electrode terminal 6 and the resin film 72 as shown in FIG. 5 . At the peripheral edge 7b, the positive electrode terminal 6 and the insulating film 9 are heat-sealed, and the resin film 72 and the insulating film 9 are also heat-sealed. Similarly, although not shown, an insulating film 9 is also provided between the negative electrode terminal 5 and the resin film 72. At the peripheral edge 7c, the negative electrode terminal 5 and the insulating film 9 are heat-sealed, and the resin film 72 and the insulating film 9 are also heat-sealed. That is, in the battery 100 shown in FIG. 5 , all of the peripheral edges 7a, 7b, and 7c of the exterior member 7 are heat-sealed.

[0095] The exterior member 7 further contains an electrolyte (not shown). The electrode group 1 is impregnated with the electrolyte.

[0096] 4 and 5, as shown in Fig. 5, a plurality of positive electrode current collecting tabs 3c are grouped together in the lowest layer of the electrode group 1. Similarly, although not shown, a plurality of negative electrode current collecting tabs are grouped together in the lowest layer of the electrode group 1. However, for example, a plurality of positive electrode current collecting tabs 3c and a plurality of negative electrode current collecting tabs can also be grouped together near the middle of the electrode group 1 and connected to the positive electrode terminal 6 and the negative electrode terminal 5, respectively.

[0097] The battery according to the embodiment can be manufactured, for example, as follows. A positive electrode, a negative electrode, and a separator are prepared. The positive electrode and the negative electrode can be manufactured, for example, by the methods described above. An electrode assembly may be manufactured using the positive electrode, the negative electrode, and the separator. At least one separator is stacked between the positive electrode and the negative electrode, and the resulting stack is pressed or spirally wound as needed to manufacture an electrode assembly. An exterior member, a positive electrode terminal, and a negative electrode terminal are also prepared. The exterior member, the positive electrode terminal, and the negative electrode terminal can be those described above. The positive electrode terminal is electrically connected to the positive electrode, and the negative electrode terminal is electrically connected to the negative electrode.

[0098] Components other than the nonaqueous electrolyte are accommodated within the exterior member. Residual moisture is removed by drying at a temperature of 95°C or higher for 6 hours or more. A separately prepared nonaqueous electrolyte is injected into the exterior member in a dry environment with a dew point of -50°C or lower, and the exterior member is sealed in a reduced pressure environment. The nonaqueous electrolyte can be prepared by dissolving an electrolyte salt and other additives in the nonaqueous solvent described above. The battery precursor obtained by sealing the other components within the exterior member is subjected to aging as follows. The battery precursor is charged so that the battery voltage becomes 2 V to 2.7 V, and then aging is performed by holding the battery precursor in a high-temperature environment of 60°C or higher and 80°C or lower for 20 hours to 100 hours or less. After aging, a portion of the exterior member is opened, and the exterior member is sealed again in a reduced pressure environment. In this way, a nonaqueous electrolyte battery according to the embodiment can be obtained.

[0099] By carrying out the aging process while the nonaqueous electrolyte battery contains an appropriate additive, a fluorine-containing coating is formed on the positive electrode surface and the negative electrode surface. Examples of such additives include difluorophosphoric acid (HPO２ F ２ ;DFP), lithium difluorophosphate (LiPO ２ F ２ Examples of fluorine-containing phosphates include lithium difluorobis(oxalate)phosphate (LiDFP), lithium difluorobis(oxalate)phosphate (LiDFBOP), and the like. One type of fluorine-containing phosphate may be added, or two or more types of fluorine-containing phosphates may be added in combination. In addition to the fluorine-containing phosphates, additives that contribute to the formation of a coating that suppresses gas generation include vinylene carbonate (C3H2O3) and trimethylvinylsilane (C5H 12 A silane compound such as LiDFBOP (LiDFBOP) may be further added. The chemical formula of LiDFBOP is as follows:

[0100]

[0101] Below, we will explain the methods for measuring the electrode active material, analyzing the electrode surface by X-ray photoelectron spectroscopy (XPS), and analyzing the electrode surface by time-of-flight secondary ion mass spectrometry (TOF-SIMS). First, we will explain the method for extracting the electrode.

[0102] <Method of removing electrodes> The battery is discharged to 1.5 V at 0.2 C to put it into a discharged state. The battery is disassembled and the electrode group is removed. From the removed electrode group, positive and negative electrodes are cut out, each approximately 2 cm square. Each cut electrode is immersed in ethyl methyl carbonate (EMC) solvent and left for 1 hour. After that, to dry the electrodes, they are vacuum-dried in a reduced pressure environment of -90 kPa for 12 hours to obtain a measurement sample. The operations up to this point are carried out in a glove box with an argon atmosphere.

[0103] <Measurement of Composition of Active Material> The composition of the active material contained in the electrode can be measured as follows.

[0104] The active material-containing layer is peeled off from the electrode as a measurement sample using, for example, a spatula to obtain a powdered sample.

[0105] The crystalline structure of the active material is identified by powder X-ray diffraction (XRD) measurement of the powder sample. The measurement is performed using CuKα radiation as a radiation source in a measurement range of 2θ from 10° to 90°. This measurement allows obtaining the X-ray diffraction pattern of the compound contained in the selected particles.

[0106] The powder X-ray diffraction measurement device used is, for example, a SmartLab manufactured by Rigaku Co., Ltd. The measurement conditions are as follows: X-ray source: Cu target, Output: 45 kV, 200 mA, Soller slit: 5° for both incident and receiving, Step width: 0.02°, Scan rate: 20° / min, Semiconductor detector: D / teX Ultra 250, Sample plate holder: Flat glass sample plate holder (thickness: 0.5 mm), Measurement range: 10°≦2θ≦90°.

[0107] When using other equipment, measurement is performed using a standard Si powder for powder X-ray diffraction so as to obtain measurement results equivalent to those described above, and the measurement is performed under conditions adjusted so that the peak intensity and peak top position coincide with those of the above equipment.

[0108] Next, the sample containing the active material is observed using a scanning electron microscope (SEM). Even during SEM observation, it is desirable to prevent the sample from coming into contact with the air and to perform the observation in an inert atmosphere such as argon or nitrogen.

[0109] For example, several particles having the form of primary particles or secondary particles that can be observed within the field of view in a 3000x SEM observation image are selected. The selected particles are selected so that the particle size distribution is as broad as possible. The observed active material particles are analyzed using energy dispersive X-ray spectroscopy (EDX) to identify the type and composition of the constituent elements of the active material. This allows the type and amount of elements other than Li contained in each selected particle to be identified. The same procedure is performed on each of multiple active material particles to determine the mixed state of the active material particles.

[0110] Next, the powder sample collected from the active material-containing layer as described above is washed with acetone and dried. The resulting powder is dissolved in hydrochloric acid, the conductive agent is removed by filtration, and the solution is diluted with ion-exchanged water to prepare a measurement sample. The metal ratio in the measurement sample is calculated using inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0111] When there are multiple types of active materials, the mass ratio is estimated from the content ratio of elements specific to each active material. The mass ratio of the specific elements to the active material is determined from the composition of the constituent elements determined by EDX analysis.

[0112] <Electrode Surface Analysis by X-ray Photoelectron Spectroscopy> Surface analysis of the electrode surface by X-ray photoelectron spectroscopy (XPS) can be performed as follows. As described above, measurement samples are cut out from the positive electrode and negative electrode, washed with EMC, and dried to obtain XPS spectra by XPS measurement. The measurement device used was a K-Alpha (manufactured by Thermo Fisher Scientific). + The measurement is carried out in an inert atmosphere.

[0113] For the positive electrode, the peak intensity P of the most intense peak in this range, which appears in the binding energy region of 682 eV to 685 eV from the obtained XPS spectrum and is a peak assigned to the Li-F bond among the 1s orbitals of F, is Li-F The peak intensity P of the most intense peak in this range, which appears in the binding energy region of 850 eV to 858 eV from the XPS spectrum obtained for the positive electrode and is assigned to the 2p3 orbital of Ni, is calculated. Ni The ratio P Li-F / P Ni Calculate.

[0114] For the negative electrode, the peak intensity N of the most intense peak in this range, which appears in the binding energy region of 682 eV to 685 eV from the obtained XPS spectrum and is a peak assigned to the Li-F bond among the F 1s orbitals, is Li-F The peak intensity N of the most intense peak in this range, which appears in the binding energy region of 454 eV to 460 eV from the XPS spectrum obtained for the negative electrode and is a peak assigned to the 2p3 orbital of Ti, is calculated. Ti The ratio N (unit: counts) is also calculated from the peak intensities. Li-F / N Ti Calculate.

[0115] <Electrode Surface Analysis by Time-of-Flight Secondary Ion Mass Spectrometry> Surface analysis of the electrode surface by time-of-flight secondary ion mass spectrometry (TOF-SIMS) can be performed as follows. Surface analysis by TOF-SIMS is performed using a measurement sample obtained by cutting out the negative electrode, washing with EMC, and drying as described above. The measurement device used is a time-of-flight secondary ion mass spectrometer TOF.SIMS manufactured by ION-TOF. 5 is used to generate primary ions. 209 Bi3 ++ The measurement area is approximately 500 μm x 500 μm.

[0116] The negative ion count NI of the peak at m / z=165 in the resulting spectrum 165 (unit: counts) and negative ion count NI of the peak at m / z = 16 16 The former m / z=165 peak represents a fluorine-containing coating on the surface of the negative electrode, and may be derived from an additive to the non-aqueous electrolyte, such as LiDFBOP. The latter m / z=16 peak represents oxygen anion O － and originates from oxygen on the negative electrode surface. From the negative ion counts obtained, the ratio of these NI 165 / NI 16 Ask for.

[0117] The nonaqueous electrolyte battery according to the first embodiment described above includes a positive electrode containing a lithium-containing nickel-cobalt-manganese oxide, a negative electrode containing a lithium-titanium-containing oxide, and a nonaqueous electrolyte. Li-F / P Ni is 0.6 or more and 1 or less, and the peak intensity ratio N Li-F / N Ti is 1.8 or more and 3 or less. According to the nonaqueous electrolyte battery, gas generation can be suppressed and the charge / discharge cycle life performance can be improved.

[0118] Second Embodiment According to a second embodiment, a battery pack is provided, which includes the nonaqueous electrolyte battery according to the first embodiment.

[0119] The battery pack according to the embodiment may include a plurality of batteries. The plurality of batteries may be electrically connected in series or in parallel. Alternatively, the plurality of batteries may be electrically connected in a combination of series and parallel. That is, the battery pack according to the embodiment may include a battery assembly. The number of battery assemblies may be multiple. The plurality of battery assemblies may be electrically connected in series, in parallel, or in a combination of series and parallel.

[0120] An example of a battery pack according to an embodiment will be described below with reference to Fig. 6 and Fig. 7. Fig. 6 is an exploded perspective view showing an example of a battery pack according to an embodiment. Fig. 7 is a block diagram showing an example of an electric circuit of the battery pack shown in Fig. 6.

[0121] 6 and 7 includes a plurality of unit cells 21. The unit cells 21 may be, for example, the flat-type battery 100 according to the embodiment described with reference to FIG.

[0122] A plurality of cells 21 are stacked so that the negative electrode terminals 5 and positive electrode terminals 6 extending outward are aligned in the same direction, and are fastened together with adhesive tape 22 to form a battery pack 23. These cells 21 are electrically connected in series with each other as shown in FIG.

[0123] The printed wiring board 24 is disposed so as to face the side surface from which the negative electrode terminal 5 and the positive electrode terminal 6 of the cell 21 extend. As shown in Fig. 7, the printed wiring board 24 is mounted with a thermistor 25, a protection circuit 26, and a terminal 27 for supplying current to an external device. An insulating plate (not shown) is attached to the surface of the printed wiring board 24 facing the assembled battery 23 to prevent unnecessary connection with the wiring of the assembled battery 23.

[0124] The positive electrode lead 28 is connected to the positive electrode terminal 6 located on the bottom layer of the battery pack 23, and its tip is inserted into and electrically connected to a positive electrode connector 29 on the printed wiring board 24. The negative electrode lead 30 is connected to the negative electrode terminal 5 located on the top layer of the battery pack 23, and its tip is inserted into and electrically connected to a negative electrode connector 31 on the printed wiring board 24. These connectors 29 and 31 are connected to the protection circuit 26 through wires 32 and 33 formed on the printed wiring board 24.

[0125] The thermistor 25 detects the temperature of the cell 21 and transmits the detection signal to the protection circuit 26. The protection circuit 26 can interrupt the positive wiring 34a and the negative wiring 34b between the protection circuit 26 and the power terminal 27 for connecting to the external device under predetermined conditions. One example of the predetermined condition is when the temperature detected by the thermistor 25 exceeds a predetermined temperature. Another example of the predetermined condition is when overcharge, overdischarge, or overcurrent of the cell 21 is detected. This overcharge detection is performed for each cell 21 or the entire battery pack 23. When detecting each cell 21, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 21. In the battery pack 20 shown in FIGS. 6 and 7, each cell 21 is connected to wiring 35 for voltage detection. A detection signal is transmitted to the protection circuit 26 via these wirings 35.

[0126] Protective sheets 36 made of rubber or resin are disposed on the three sides of the battery pack 23 excluding the sides from which the positive electrode terminal 6 and the negative electrode terminal 5 protrude.

[0127] The battery pack 23 is housed in a container 37 together with the protective sheets 36 and the printed wiring board 24. That is, the protective sheets 36 are disposed on both inner surfaces along the long sides and the inner surface along the short sides of the container 37, and the printed wiring board 24 is disposed on the inner surface along the other short side on the opposite side across the battery pack 23. The battery pack 23 is located in a space surrounded by the protective sheets 36 and the printed wiring board 24. A lid 38 is attached to the top surface of the container 37.

[0128] Heat-shrinkable tape may be used to secure the battery pack 23 instead of the adhesive tape 22. In this case, protective sheets are placed on both sides of the battery pack, and the heat-shrinkable tape is wrapped around the battery pack, and then the heat-shrinkable tape is thermally shrunk to bind the battery pack.

[0129] 6 and 7 show the cells 21 electrically connected in series, the cells 21 may be electrically connected in parallel to increase the battery capacity. Furthermore, the assembled battery pack may be electrically connected in series and / or in parallel.

[0130] Furthermore, the configuration of the battery pack according to the embodiment may be appropriately changed depending on the application. The battery pack according to the embodiment is preferably used in applications where cycle performance in large current charging and discharging is desired. Specific applications include power sources for digital cameras and in-vehicle applications such as two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, and power-assisted bicycles. In-vehicle applications are particularly suitable for the battery pack according to the embodiment.

[0131] The battery pack according to the second embodiment includes the battery according to the first embodiment, and therefore has excellent life performance.

[0132] The examples will be described in detail below.

[0133] Example 1: LiNi as a positive electrode active material 0.33 Co 0.33 Mn 0.33A lithium-containing nickel-cobalt-manganese oxide represented by O2 was prepared. Acetylene black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder were dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 90:5:5 for the positive electrode active material. The resulting dispersion was applied to a current collector made of aluminum foil with a thickness of 15 μm, dried, and pressed to form a positive electrode active material-containing layer. The basis weight per side of the positive electrode was 80 g / m. 2 It was.

[0134] As the negative electrode active material, Li4Ti5O 12 A lithium titanate represented by the formula (1) was prepared. Graphite as a conductive agent and polyvinylidene fluoride as a binder were dispersed in N-methylpyrrolidone (NMP) at a mass ratio of 95:3:2 for the negative electrode active material. The resulting dispersion was applied to a current collector made of aluminum foil with a thickness of 15 μm, dried, and pressed to form a negative electrode active material-containing layer. The basis weight per side of the negative electrode was 80 g / m. 2 It was.

[0135] A 15 μm thick resin separator was prepared as the separator. The separator was folded zigzag so that the separator was disposed between the positive electrode and the negative electrode, and these components were stacked. The resulting stack was wound to prepare a spiral electrode assembly.

[0136] As a non-aqueous electrolyte, an electrolyte solution was prepared as follows: 1 mol / L LiPF 6 in a mixed solvent of diethyl carbonate (DEC) and ethylene carbonate (EC). ６ The mixture was dissolved in 1% by mass of lithium difluorophosphate (LiDFP) and 1% by mass of lithium difluorobis(oxalate)phosphate (LiDFBOP) and mixed. The proportion of DEC in the mixed solvent was 70% by volume, and the proportion of EC was 30% by volume.

[0137] Two quadrilateral laminate films were prepared. One laminate film was placed above and below the electrode group, and the three overlapping sides of the films were heat-sealed to obtain an electrode group wrapped in an outer container made of laminate film. This was placed in a dryer and vacuum-dried at 95°C for 12 hours. After drying, the electrode group was transported to a glove box with a dew point controlled at -50°C or below. The prepared electrolyte solution was poured into the container. In a reduced pressure environment of -90 kPa, the remaining overlapping side of the films was heat-sealed to seal the outer container.

[0138] After the electrolyte injection, the battery was initially charged at 1 C to a battery voltage of 2.7 V, and then aged for 24 hours in a thermostatic chamber at 70° C. After aging, one side of the laminate film container was opened and the container was sealed again in a reduced pressure environment of −90 kPa to prepare a nonaqueous electrolyte battery.

[0139] Examples 2 and 3 Non-aqueous electrolyte batteries were fabricated in the same manner as in Example 1, except that the aging conditions were changed as shown in Table 1 below.

[0140] Examples 4 to 6 Non-aqueous electrolyte batteries were fabricated in the same manner as in Example 1, except that the amount of LiDFBOP added to the electrolyte and the aging conditions were changed as shown in Table 1 below.

[0141] Example 7 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that EC in the mixed solvent used to prepare the electrolyte solution was changed to propylene carbonate (PC).

[0142] Example 8 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the amount of LiDFP added to the electrolyte solution was changed as shown in Table 1 below.

[0143] Comparative Examples 1 and 2 Non-aqueous electrolyte batteries were fabricated in the same manner as in Example 1, except that the amount of LiDFBOP added to the electrolyte and the aging conditions were changed as shown in Table 1 below.

[0144] Comparative Example 3 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the aging conditions were changed as shown in Table 1 below.

[0145] Comparative Example 4 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the addition of LiDFBOP to the electrolyte solution was omitted.

[0146] Comparative Examples 5 and 6 Non-aqueous electrolyte batteries were fabricated in the same manner as in Example 1, except that DEC in the mixed solvent used to prepare the electrolyte solution was changed to ethyl propionate (EP).

[0147] Comparative Example 7 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that in the mixed solvent used to prepare the electrolyte solution, DEC was changed to ethyl propionate (EP) and the amount of LiDFP added was omitted.

[0148] Comparative Example 8 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the amount of LiDFBOP added to the electrolyte and the aging conditions were changed as shown in Table 1 below.

[0149]

[0150] <Electrode Surface Analysis by X-ray Photoelectron Spectroscopy> The positive and negative electrodes of the nonaqueous electrolyte batteries prepared in each example were subjected to surface analysis by X-ray photoelectron spectroscopy (XPS) as described above. The results are shown in Table 2 below.

[0151] <Electrode Surface Analysis by Time-of-Flight Secondary Ion Mass Spectrometry> The negative electrodes of the nonaqueous electrolyte batteries prepared in each example were subjected to surface analysis by time-of-flight secondary ion mass spectrometry (TOF-SIMS) as described above. The results are shown in Table 2 below.

[0152] <Evaluation of cycle performance> 1C constant current charge / discharge cycles were carried out in a voltage range of 1.5V to 2.7V in an environment of 45°C. The amount of gas in the battery cell after 1000 cycles was measured. The measurement results are shown in Table 2 below.

[0153]

[0154] As shown in Table 2, compared to the batteries fabricated in Examples 1 to 8, the batteries fabricated in Comparative Examples 1 to 8 generated larger amounts of gas.

[0155] In Comparative Examples 1, 2, and 4, the ratio N Li-F / N TiSince the ratio P was less than 1.8, it can be seen that the coating of the negative electrode active material containing layer was insufficient. In these examples, the fluorine-containing coating on the negative electrode was insufficient, and therefore gas generation was not effectively suppressed. Ni / N Ti Since the CO generation at the negative electrode was low, it was confirmed that the CO generation at the positive electrode ２ The amount of gas generated was particularly large, exceeding that of oxidation treatment.

[0156] In Comparative Example 3, the ratio P Li-F / P Ni is less than 0.6, and the ratio N Li-F / N Ti In Comparative Example 3, the suppression of gas generation from both the positive electrode and the negative electrode was insufficient, resulting in a significantly increased amount of gas generation.

[0157] In Comparative Examples 5 to 7, the ratio P Li-F / P Ni In these examples, the ratio of the fluorine-containing coating on the positive electrode surface was high. ２ The oxidation treatment of the material was insufficient, resulting in a large amount of gas being generated.

[0158] In Comparative Example 8, the ratio N Li-F / N Ti The fact that the value of the fluorine-containing coating film was greater than 3 indicates that the negative electrode active material-containing layer was excessively coated with the fluorine-containing coating film. This resulted in an increase in the electrical resistance of the negative electrode, which in turn promoted side reactions at the negative electrode and increased the amount of gas generated.

[0159] In the nonaqueous electrolyte battery according to at least one of the embodiments and examples described above, the peak intensity ratio P Li-F / P Ni is 0.6 or more and 1 or less, and the peak intensity ratio N Li-F / N Ti is 1.8 or more and 3 or less. Therefore, the nonaqueous electrolyte battery has an excellent cycle life.

[0160] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0161]

[0023] The following describes some embodiments of the present invention. [1] A positive electrode containing a lithium-containing nickel-cobalt-manganese oxide, a negative electrode containing a lithium-titanium-containing oxide, and a non-aqueous electrolyte, wherein the peak intensity P of the most intense peak appearing in the range of 850 eV to 858 eV in an X-ray photoelectron spectrum of the positive electrode surface of the positive electrode is 0.01 eV. Ni The peak intensity P of the most intense peak appearing in the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the positive electrode surface Li-F The ratio P Li-F / P Ni is 0.6 or more and 1 or less, and the peak intensity N of the most intense peak appearing in the range of 454 eV to 460 eV in the X-ray photoelectron spectrum of the negative electrode surface of the negative electrode Ti The peak intensity N of the most intense peak appearing in the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the negative electrode surface Li-F Ratio of N Li-F / N Ti [2] The peak intensity N Ti The peak intensity P Ni The ratio P Ni / N Ti [3] The negative ion count NI at m / z=165 in time-of-flight secondary ion mass spectrometry of the negative electrode surface is 1.2 or more and 1.5 or less. 165 and m / z=16 negative ion count NI 16 and 0.12 < NI 165 / NI 16The nonaqueous electrolyte battery according to [1] or [2], wherein the relationship of .lambda.<0.18 is satisfied. [4] A battery pack comprising the nonaqueous electrolyte battery according to any one of [1] to [3].

[0162] DESCRIPTION OF SYMBOLS 1...electrode group, 2...negative electrode, 2a...negative electrode current collector, 2b...negative electrode active material-containing layer, 3...positive electrode, 3a...positive electrode current collector, 3b...positive electrode active material-containing layer, 3c...positive electrode current collecting tab, 4...separator, 5...negative electrode terminal, 6...positive electrode terminal, 7...exterior member, 15...negative electrode terminal, 15a...negative electrode lead, 16...positive electrode terminal, 16a...positive electrode lead, 17a...metallic container, 17b...sealing plate, 17c...insulating member, 20...battery pack, 23...assembled battery, 24...printed wiring board, 25...thermistor, 26...protective circuit, 27...current-carrying terminal, 28...positive electrode side lead, 30...negative electrode side lead, 36...protective sheet, 37...container, 38...lid

Claims

1. A positive electrode containing a lithium-containing nickel-cobalt-manganese oxide, a negative electrode containing a lithium-titanium-containing oxide, and a non-aqueous electrolyte, wherein the peak intensity P of the most intense peak appearing in the range of 850 eV to 858 eV in an X-ray photoelectron spectrum of the positive electrode surface of the positive electrode is Ni The peak intensity P of the most intense peak appearing in the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the positive electrode surface Li-F The ratio P Li-F / P Ni is 0.6 or more and 1 or less, and the peak intensity N of the most intense peak appearing in the range of 454 eV to 460 eV in the X-ray photoelectron spectrum of the negative electrode surface of the negative electrode Ti The peak intensity N of the most intense peak appearing in the range of 682 eV to 685 eV in the X-ray photoelectron spectrum of the negative electrode surface Li-F Ratio of N Li-F / N Ti is 1.8 or more and 3 or less.

2. The peak intensity N Ti The peak intensity P Ni The ratio P Ni / N Ti 2. The nonaqueous electrolyte battery according to claim 1, wherein the σ is 1.2 or more and 1.5 or less.

3. Negative ion count NI of m / z=165 in time-of-flight secondary ion mass spectrometry of the negative electrode surface 165 and m / z=16 negative ion count NI 16 and 0.12 < NI 165 / NI 16 3. The nonaqueous electrolyte battery according to claim 1, wherein the relationship of .lambda.<0.18 is satisfied.

4. A battery pack comprising the nonaqueous electrolyte battery according to claim 1 or 2.

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