JP6479943B2 - Nonaqueous electrolyte battery and battery pack - Google Patents

Description

  Embodiments described herein relate generally to a nonaqueous electrolyte battery and a battery pack.

  The use of a separator in which the pore diameter of 1 μm or more occupies most of the pore volume ratio is advantageous for extending the battery life and improving the impregnation of the electrolyte. However, when such a separator is used, there is a problem that there is a high possibility that the positive electrode and the negative electrode are in contact with each other, and as a result, there is a high possibility that a cell having a large self-discharge amount is generated.

JP 2009-81048 A JP 2009-141181 A JP 2011-54503 A

  The problem to be solved by the present invention is to provide a non-aqueous electrolyte battery that has excellent life characteristics and can suppress self-discharge.

According to the first embodiment, a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The negative electrode has a Li storage potential of 1 V vs. The negative electrode active material which is more than Li / Li ⁺ is included. The negative electrode has an electric resistance in a state of 100 Ω · cm to 100000 Ω · cm in a discharged state. In the separator, the pore volume ratio of pores having a pore diameter of 1 μm or more is larger than 70%. This pore volume ratio is obtained from an integrated pore volume frequency curve obtained by mercury porosimetry. The pore diameter distribution curve obtained by the mercury intrusion method of the separator has a mode diameter in the range of 1.1 to 7.8 μm.

  According to the second embodiment, a battery pack is provided. This battery pack includes the nonaqueous electrolyte battery according to the first embodiment.

FIG. 1 is an exploded perspective view of an example nonaqueous electrolyte battery according to the first embodiment. FIG. 2 is a partially developed perspective view of an electrode group included in the nonaqueous electrolyte battery shown in FIG. FIG. 3 is an exploded perspective view of an example battery pack according to the second embodiment. FIG. 4 is a block diagram showing an electric circuit of the battery pack of FIG. FIG. 5 is an integrated pore volume frequency curve of the separator included in the nonaqueous electrolyte battery of Example 1. 6 is a pore diameter distribution curve of a separator provided in the nonaqueous electrolyte battery of Example 1. FIG.

  Hereinafter, embodiments will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the embodiment, and its shape, dimensions, ratio, etc. are different from the actual device, but these are the following explanations and known techniques. The design can be changed as appropriate.

(First embodiment)
According to the first embodiment, a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The negative electrode has a Li storage potential of 1 V vs. The negative electrode active material which is more than Li / Li ⁺ is included. The negative electrode has an electric resistance in a discharged state of 100 Ω · cm to 100,000 Ω · cm. In the separator, the pore volume ratio of pores having a pore diameter of 1 μm or more is larger than 70%. This pore volume ratio is obtained from an integrated pore volume frequency curve obtained by mercury porosimetry.

The inventors have determined that the Li storage potential of the negative electrode active material of the nonaqueous electrolyte battery is 1 V vs. In addition to using a negative electrode active material of Li / Li ⁺ or more, a separator in which pores having a pore diameter of 1 μm or more occupy most of the pore volume of the separator is used, and further, the electrical resistance of the negative electrode in the discharge state is 100Ω · It has been found that a battery having excellent life characteristics and less self-discharge can be realized by setting it within the range of cm to 100,000 Ω · cm.

  Here, the separator in which the pores having a pore diameter of 1 μm or more occupy most of the pore volume of the separator specifically means that the pores having a pore diameter of 1 μm or more of the total pore volume of the separator. It means a separator that occupies more than 70% of the volume. In such a separator, the pore volume ratio of pores having a pore diameter of 1 μm or more is larger than 70%. This pore volume ratio is obtained from an integrated pore volume frequency curve obtained from pore diameter distribution measurement by a mercury intrusion method of the separator.

  In a nonaqueous electrolyte battery, when a charge / discharge cycle is repeated, a by-product generated by a side reaction of the battery reaction accumulates in the pores of the separator, and as a result, the separator may be clogged. When the separator is clogged, battery resistance may increase. However, a separator having a pore diameter ratio of 1 μm or more and a pore volume ratio larger than 70% can prevent such clogging of the separator, and thus suppress an increase in battery resistance.

  Moreover, when a negative electrode contacts a positive electrode through the through-hole part of a separator, the contact part will be in a discharge state rapidly. Since the negative electrode included in the non-aqueous electrolyte according to the first embodiment has an electric resistance in a discharged state in a range of 100 Ω · cm to 100000 Ω · cm, a portion of the negative electrode that is in a discharged state serves as an insulator. be able to. Thanks to the part of the negative electrode that is in a discharged state, the self-discharge caused by contact with the positive electrode stops with little progress. That is, the portion of the negative electrode that is in a discharged state can prevent further self-discharge of the nonaqueous electrolyte battery from proceeding.

Furthermore, the Li storage potential of the negative electrode active material of the nonaqueous electrolyte battery is 1 V vs. By using a negative electrode active material that is equal to or higher than Li / Li ^+, it is possible to suppress the precipitation of lithium dendride due to the charge / discharge cycle. As a result, it is possible to avoid dangers such as a short circuit, self-discharge and ignition due to the precipitation of lithium dendride.

  Thanks to these, the nonaqueous electrolyte battery according to the first embodiment can exhibit excellent life characteristics and suppress self-discharge.

  When the pore volume ratio of pores having a pore diameter of 1 μm or more is smaller than 70%, the separator is easily clogged. As a result, the resistance of the battery may increase. The pore volume ratio of pores having a pore diameter of 1 μm or more of the separator is preferably 99% or less.

  The separator preferably has a mode diameter in the range of 1 to 20 μm. The mode diameter of the separator is the pore diameter having the largest pore volume in the pore diameter distribution curve obtained by the mercury intrusion method of the separator, that is, the mode pore diameter. A separator having a mode diameter in the range of 1 to 20 μm can further suppress an increase in resistance due to clogging of the separator and self-discharge.

  The separator preferably has a thickness in the range of 3 to 25 μm. A separator having a thickness in the range of 3 to 25 μm can further suppress an increase in resistance due to clogging of the separator and self-discharge.

  If the electrical resistance in the discharge state of the negative electrode is smaller than 100 Ω · cm, the self-discharge reaction that occurs when the positive electrode and the negative electrode come into contact with each other at the through-hole portion of the separator may proceed until the entire battery is discharged. On the other hand, if the electrical resistance of the negative electrode in the discharge state is greater than 100,000 Ω · cm, the negative electrode resistance is too high and the output characteristics are degraded. A more preferable range of the electric resistance in the discharge state of the negative electrode is 200Ω · cm to 10000Ω · cm.

Li storage potential of the negative electrode active material of the non-aqueous electrolyte battery is 1 V vs. When a negative electrode active material that is less than Li / Li ⁺ is used, lithium dendride can be deposited on the surface of the negative electrode by a charge / discharge cycle. Lithium dendrites can cause short circuits, self-discharge and ignition of non-aqueous electrolyte batteries.

The pore state of the separator can be adjusted by combining various factors.
For example, the pore state of the separator includes the raw material fiber diameter [μm], fiber length [μm], mixing ratio of raw materials with different materials and shapes, basis weight [g / m ² ], separator thickness [μm], It can be adjusted by devising and combining conditions such as density [g / cm ³ ] and the manufacturing method of the separator.

The electrical resistance in the discharge state of the negative electrode can be controlled by combining various factors.
For example, the electrical resistance in the discharge state of the negative electrode can be controlled by the electrical resistance of the negative electrode active material itself, the electrical resistance of the conductive agent mixed in the negative electrode active material, and the mixing ratio of these in the negative electrode.

For example, mixing using spinel type lithium titanium composite oxide Li _{4 + x} Ti ₅ O ₁₂ (x varies in the range of −1 ≦ x ≦ 3 by charge / discharge reaction) as a negative electrode active material and graphite as a conductive agent The case of an electrode will be described as an example. The spinel type lithium titanium composite oxide is an insulator in a discharged state. Here, the specific surface area of the spinel type lithium titanium composite oxide is A [m ² / g], the weight content ratio of the spinel type lithium titanium composite oxide in the electrode layer is B, and the specific surface area of graphite is C [m. ² / g] and D is the weight content of graphite in the electrode layer. In such a negative electrode, when the AB / CD value is in the range of 4 to 25, the electric resistance in the discharge state of the negative electrode can be in the range of 100 Ω · cm to 100,000 Ω · cm. However, the electrical resistance may change depending on the negative electrode density and the dispersion state of the active material and the conductive agent.

  The pore diameter distribution of the separator by the mercury intrusion method can be measured by the following method.

  First, the nonaqueous electrolyte battery is disassembled. For example, the battery can be disassembled in an inert atmosphere such as argon. Next, the electrode group is taken out from the disassembled nonaqueous electrolyte battery. A separator is taken out from the taken-out electrode group using tweezers or the like. The removed separator is washed with methyl ethyl carbonate to remove Li salt in the separator. After washing, the separator is dried to obtain a measurement sample.

  Next, the measurement sample is loaded into the measurement analyzer. Examples of the measuring device include a pore distribution measuring device Autopore 9520 manufactured by Shimadzu Corporation. When measuring with this apparatus, the pore diameter distribution can be measured by folding a measurement sample into a sample cell of this apparatus into a size of about 25 mm and folding it.

  From the pore diameter distribution of the separator thus obtained, an integrated pore volume frequency curve and a pore diameter distribution curve are obtained.

  From the cumulative pore volume frequency curve thus obtained, the pore volume ratio of pores having a measured separator pore diameter of 1 μm or more can be determined.

  Moreover, the measured mode diameter of the separator can be obtained from the pore diameter distribution curve thus obtained.

  Next, a method for measuring the electrical resistance of the negative electrode in the discharged state will be described.

First, an appropriate resistance is connected to the battery at room temperature, and discharging is performed until the battery voltage (open circuit voltage) reaches 1V. The battery thus discharged is then disassembled as described above. Next, the electrode group is taken out from the disassembled battery, and the negative electrode is taken out from the taken out electrode group. Next, the Li electrode in the negative electrode is removed by washing the extracted electrode with methyl ethyl carbonate. The washed negative electrode is dried, and then the negative electrode is sandwiched between leads having a certain area, and a certain pressure, for example, 50 kgf / cm ² is applied in this state. Next, the lead that contacts each of the front and back surfaces of the negative electrode is connected to the Wheatstone bridge, and the resistance is measured.

When the electrical resistance that can be read from the Wheatstone bridge is R [Ω], the electrode area of the measurement part is S [cm ² ], and the electrode thickness is T [cm], the electrical resistivity [Ω · cm] is calculated by the following formula: The

Electrical resistivity [Ω · cm] = S [cm ² ] × R [Ω] / T [cm]
The electrical resistance calculated in this way is the electrical resistance of the negative electrode in the discharged state.

  The thickness of the separator can be measured by the following procedure. A separator with a length of 500 mm is folded into 10 sheets so that the crease is perpendicular to the length direction, and the thickness is measured with an outer micrometer defined by JIS B7502 (spindle diameter 6.35 mm, measurement length 25 mm or less). . The quotient obtained by dividing the value thus obtained by 10 is defined as the separator thickness.

  Next, the nonaqueous electrolyte battery according to the first embodiment will be described in detail.

  The nonaqueous electrolyte battery according to the first embodiment includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte.

  The positive electrode can include a positive electrode current collector and a positive electrode material layer (positive electrode active material-containing layer) carried on one or both surfaces of the positive electrode current collector.

  The positive electrode material layer can include a positive electrode active material. The positive electrode material layer can further contain a conductive agent and a binder as necessary.

  The positive electrode current collector can also include a portion that does not carry the positive electrode material layer on the surface. The portion of the positive electrode current collector that does not carry the positive electrode material layer can serve as a positive electrode tab. Alternatively, the positive electrode can include a positive electrode tab separate from the positive electrode current collector.

  The negative electrode can include a negative electrode current collector and a negative electrode material layer (negative electrode active material-containing layer) carried on one or both surfaces of the negative electrode current collector.

The negative electrode material layer can include a negative electrode active material. Li storage potential is 1 V vs. The negative electrode active material that is greater than or equal to Li / Li ⁺ can be included in the negative electrode material layer. The negative electrode material layer can further contain a conductive agent and a binder as necessary.

  The negative electrode current collector can include a portion that does not carry the negative electrode material layer on the surface. This part can serve as a negative electrode tab. Alternatively, the negative electrode can include a negative electrode tab separate from the negative electrode current collector.

  The separator is interposed between the positive electrode and the negative electrode. Thereby, the positive electrode material layer and the negative electrode material layer can be opposed to each other via the separator.

  The positive electrode, the negative electrode, and the separator can constitute an electrode group. The electrode group can have various structures. For example, the electrode group can have a stacked structure. A stack type electrode group can be obtained, for example, by laminating a plurality of positive electrodes and negative electrodes with a separator interposed between a positive electrode material layer and a negative electrode material layer. Alternatively, the electrode group can have a wound structure. For example, a wound electrode group is formed by laminating one separator, one positive electrode, another separator, and one negative electrode in this order. It can obtain by winding so that a negative electrode may come outside.

  A non-aqueous electrolyte can be impregnated in such an electrode group.

  The nonaqueous electrolyte battery according to the first embodiment can further include a positive electrode terminal and a negative electrode terminal.

  The positive electrode terminal can function as a conductor for electrons to move between the positive electrode and an external circuit by being partly connected to a part of the positive electrode. The positive electrode terminal can be connected to, for example, a positive electrode current collector, particularly a positive electrode tab. Similarly, a part of the negative electrode terminal is electrically connected to a part of the negative electrode, whereby the negative electrode terminal can serve as a conductor for electrons to move between the negative electrode and the external terminal. The negative electrode terminal can be connected to, for example, a negative electrode current collector, particularly a negative electrode tab.

  The nonaqueous electrolyte battery according to the first embodiment can further include an exterior member. The exterior member can accommodate the electrode group and the nonaqueous electrolyte. A part of each of the positive electrode terminal and the negative electrode terminal can be extended from the exterior member.

  Hereinafter, the nonaqueous electrolyte battery according to the first embodiment will be described in detail for each member.

1) Negative electrode For the negative electrode current collector, for example, a metal foil or an alloy foil is used. Aluminum foil or aluminum alloy foil is particularly preferable. The aluminum foil and aluminum alloy foil desirably have an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and still more preferably 5 μm or less. By setting the average crystal grain size of the aluminum foil or aluminum alloy foil to 50 μm or less, the strength of the aluminum foil or aluminum alloy foil can be dramatically increased. For this reason, it is possible to increase the negative electrode capacity by increasing the pressure during pressing to increase the density of the negative electrode material layer. Further, it is possible to prevent deterioration due to dissolution and corrosion of the current collector in an overdischarge cycle under a high temperature environment (40 ° C. or higher). For this reason, an increase in negative electrode impedance can be suppressed. Furthermore, output performance, rapid charge, and charge / discharge cycle performance can also be improved.

The average crystal grain size is determined as follows. The structure of the current collector surface is observed with an optical microscope, and the number n of crystal grains existing within 1 mm × 1 mm is determined. Using this n, the average crystal grain area S is determined from S = 1 × 10 ⁶ / n (μm ² ). The average crystal particle diameter d (μm) is calculated from the obtained S value by the following formula (A).

d = 2 (S / π) ^1/2 (A)
The average crystal grain size of the aluminum foil or aluminum alloy foil changes under complex influences from a plurality of factors such as material structure, impurities, processing conditions, heat treatment history, and annealing conditions. The crystal grain size can be adjusted by controlling the above factors in combination during the production process of the current collector.

  The thickness of the current collector is desirably 20 μm or less, more preferably 15 μm or less. The aluminum foil preferably has a purity of 99% by mass or more. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. Transition metals such as iron, copper, nickel and chromium contained as alloy components are preferably 1% by mass or less.

As described above, the negative electrode active material has a Li storage potential of 1 V vs. A negative electrode active material that is Li / Li ⁺ or higher, that is, a negative electrode active material capable of charge / discharge reaction at a potential of 1 V or higher (preferably 1.1 V or higher and 3 V or lower) with respect to lithium.

  Here, a method for measuring the reaction potential will be described. First, a three-electrode cell having a negative electrode active material to be measured as a working electrode and metallic lithium as a counter electrode and a reference electrode is prepared. In this three-electrode type cell, lithium insertion / extraction reaction is performed at a current value of 1/10 of the electric capacity of the working electrode, that is, at a 0.1 C rate. The average operating potential in the lithium elimination reaction at this time is defined as the reaction potential of the negative electrode active material. Here, the 1C rate is defined as the 1C rate as the current value required to discharge the electrode capacitance in one hour, and the ratio of the actual current value to the 1C rate is defined as the rate of the current value.

Li storage potential is 1 V vs. Examples of the negative electrode active material that is greater than or equal to Li / Li ⁺ include spinel type lithium titanium composite oxide. Examples of the spinel-type lithium titanium composite oxide include Li _{4 + x} Ti ₅ O ₁₂ (x varies in the range of 0 ≦ x ≦ 3 due to charge / discharge reaction).

Other Li storage potentials are 1 V vs. Examples of the negative electrode active material that is greater than or equal to Li / Li ⁺ include lithium compounds that can occlude and release lithium. Examples of such lithium compounds include lithium oxide, lithium sulfide, and lithium nitride. Among these, a metal compound that does not contain lithium in an uncharged state, but also includes a compound that contains lithium when charged.

Examples of the oxide that contains lithium by charging include titanium-containing metal composite oxides, for example, amorphous tin oxides such as SnB _0.4 P _0.6 O _3.1 , tin oxides such as SnSiO _3, and SiO. Examples thereof include silicon oxide, for example, tungsten oxide such as WO ₃ . Of these, titanium-containing metal composite oxides are preferable.

Examples of the titanium-containing metal composite oxide include lithium titanium oxide, and titanium-based oxides that do not contain lithium during oxide synthesis. Examples of lithium titanium oxides other than the spinel-type lithium titanium composite oxide include lithium titanate having a ramsdellite structure. Examples of lithium titanate having a ramsdellite structure include Li _{2 + y} Ti ₃ O ₇ (y varies within a range of −1 ≦ y ≦ 3 due to charge / discharge reaction). Examples of the titanium-based oxide include metal composite oxides containing TiO ₂ , Ti, and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, Nb, and Fe. TiO ₂ is preferably anatase type and low crystalline having a heat treatment temperature of 300 to 500 ° C. Examples of the metal composite oxide containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, Nb, and Fe include TiO ₂ —P ₂ O ₅ , TiO _{2. -V 2 O 5, TiO 2 -P} 2 O 5 -SnO 2, TiO 2 -P 2 O 5 -MeO (Me is at least one element selected from the group consisting of Cu, Ni and Fe) Nb ₂ TiO _{7 and the} like. This metal composite oxide has a low crystallinity and preferably has a microstructure in which a crystal phase and an amorphous phase coexist or exist as an amorphous phase alone. With such a microstructure, cycle performance can be greatly improved. Among these, a metal composite oxide containing lithium titanium oxide and Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, Nb, and Fe is preferable.

Examples of the sulfide include titanium sulfide such as TiS ₂ , molybdenum sulfide such as MoS _2, and iron sulfide such as FeS, FeS ₂ , and Li _x FeS ₂ (0 ≦ x ≦ 2).

Examples of the nitride include lithium cobalt nitride (for example, Li _x Co _y N, where 0 <x <4 and 0 <y <0.5).

  These active materials may be used alone or in combination of two or more.

  Examples of the conductive agent include carbon black, graphite (graphite), graphene, fullerenes, coke, carbon fiber, and metal powder. Among these, carbon black, graphite, and graphene are preferable, and examples of carbon black include acetylene black, ketjen black, and furnace black.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), acrylic resin, polyolefin resin, polyurethane resin, polyimide resin, fluorine rubber, and styrene butadiene rubber.

  For example, the negative electrode is prepared by adding a conductive agent and a binder to a powdered negative electrode active material, suspending them in a suitable solvent, applying the suspension (slurry) to a current collector, drying, and pressing. It can be produced by forming a strip electrode.

  At this time, the mixing ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 73 to 98% by weight of the negative electrode active material, 0 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder. .

2) Positive electrode Examples of the positive electrode active material include various oxides and sulfides. For example, manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (eg, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxide (eg, Li _x NiO ₂₎ ), Lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel cobalt composite oxide (eg, Li _x Ni _1-yz Co _y M _z O ₂ (M is at least selected from the group consisting of Al, Cr and Fe) 1 element, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.1)), lithium manganese cobalt composite oxide (for example, Li _x Mn _1-yz Co _y M _z O ₂ ( M is at least one element selected from the group consisting of Al, Cr and Fe, and 0 ≦ y ≦ 0.5 and 0 ≦ z ≦ 0.1)), lithium manganese nickel composite compound (for example, Li _x Mn _1/2 Ni _1/2 O ₂ ), spinel-type lithium manganese nickel composite oxide (for example, Li _x Mn _2-y Ni _y O ₄ ), lithium phosphorus oxide having an olivine structure (for example, Li _x such as _{FePO 4, Li x Fe 1-} y Mn y PO 4, Li x CoPO 4), iron sulfate (e.g. _{Fe 2 (SO 4) 3)} , vanadium oxide (e.g. V ₂ O _5), and the like. In addition, conductive polymer materials such as polyaniline and polypyrrole, disulfide-based polymer materials, organic materials such as sulfur (S) and carbon fluoride, and inorganic materials are also included. In addition, about x, y, and z for which there is no description of a preferable range above, it is preferable that it is the range of 0-1.

  The type of the positive electrode active material can be one type or two or more types.

  Examples of the conductive agent include carbon black, graphite (graphite), graphene, fullerenes, coke, carbon fiber, and metal powder. Among these, carbon black and graphite are preferable, and examples of the carbon black include acetylene black, ketjen black, and furnace black.

  Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), acrylic resin, polyolefin resin, polyurethane resin, polyimide resin, fluorine rubber, and styrene butadiene rubber.

  The positive electrode current collector is preferably formed from an aluminum foil or an aluminum alloy foil. The average crystal grain size of the aluminum foil and the aluminum alloy foil is preferably 50 μm or less. More preferably, it is 30 μm or less. More preferably, it is 5 μm or less. When the average crystal grain size is 50 μm or less, the strength of the aluminum foil or aluminum alloy foil can be dramatically increased, the positive electrode can be densified with a high press pressure, and the battery capacity is increased. Can be made.

  The thickness of the current collector is 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. As the aluminum alloy, an alloy containing elements such as magnesium, zinc and silicon is preferable. On the other hand, the content of transition metals such as iron, copper, nickel and chromium is preferably 1% by mass or less.

  For this positive electrode, for example, a conductive agent and a binder are added to the positive electrode active material, these are suspended in a suitable solvent, and this suspension is applied to a current collector such as an aluminum foil, dried and pressed. It is produced by forming a strip electrode.

  At this time, the mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder. .

3) Nonaqueous electrolyte This nonaqueous electrolyte can contain a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. Further, the non-aqueous solvent may contain a polymer. However, it is preferable that a Li salt having B is contained as an electrolyte salt.

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , Li (CF ₃ SO ₂ ) ₂ N (bistrifluoromethanesulfonylamide lithium; commonly known as LiTFSI), LiCF ₃ SO ₃ (commonly known as LiTFS), and Li (C ₂ F ₅ SO _{2) 2} N (bis pentafluoroethanesulfonyl amide lithium; called _{LiBETI), LiClO 4, LiAsF 6} , LiSbF 6, bisoxalato Lato lithium borate _{(LiB (C 2 O 4)} 2 ( known as LiBOB)), difluoro (oxalato) Lithium borate (LiF ₂ BC ₂ O ₄ ), difluoro (trifluoro-2-oxide-2-trifluoro-methylpropionate (2-)-0,0) lithium borate (LiBF ₂ (OCOOC (CF ₃ ) ₂₎ (aka LiBF ₂ (HHIB))), lithium difluorophosphate (LiPO _{2 2)} lithium salts, and the like. These electrolyte salts may be used alone or in combination of two or more. In particular, LiPF ₆ , LiBF ₄ , lithium bisoxalatoborate (LiB (C ₂ O ₄ ) ₂ (common name LiBOB)), lithium difluoro (oxalato) borate (LiF ₂ BC ₂ O ₄ ), difluoro (trifluoro-2 -Oxido-2-trifluoro-methylpropionate (2-)-0,0) lithium borate (LiBF ₂ (OCOOC (CF ₃ ) ₂ ) (commonly known as LiBF ₂ (HHIB))), lithium difluorophosphate (LiPO ₂ F ₂ ) is preferred.

  The electrolyte salt concentration is preferably in the range of 0.5M to 3.0M. Thereby, the performance when a high load current is passed can be improved.

  The non-aqueous solvent is not particularly limited, but propylene carbonate (PC), ethylene carbonate (EC), 1,2-dimethoxyethane (DME), γ-butyrolactone (GBL), tetrahydrofuran (THF), 2 -Methyltetrahydrofuran (2-MeHF), 1,3-dioxolane, sulfolane, acetonitrile (AN), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), dipropyl carbonate (DPC), etc. It is done. These solvents may be used alone or in combination of two or more. Further, when two or more kinds of solvents are combined, it is preferable to select from all solvents having a dielectric constant of 20 or more.

  An additive may be added to the non-aqueous electrolyte. Although it does not specifically limit as an additive, Vinylene carbonate (VC), fluoro vinylene carbonate, methyl vinylene carbonate, fluoromethyl vinylene carbonate, ethyl vinylene carbonate, propyl vinylene carbonate, butyl vinylene carbonate, dimethyl vinylene carbonate, diethyl Examples include vinylene carbonate, dipropyl vinylene carbonate, vinylene acetate (VA), vinylene butyrate, vinylene hexanate, vinylene crotonate, catechol carbonate, propane sultone, and butane sultone. One kind or two or more kinds of additives can be used.

4) Separator The material of the separator is not particularly limited. For example, a porous film or a nonwoven fabric made of a polymer such as polyolefin, cellulose, polyester, polyvinyl alcohol, polyamide, polytetrafluoroethylene, and vinylon can be used. . Inorganic particles may be contained in the porous film or nonwoven fabric. One type of separator material may be used, or two or more types may be used in combination.

5) Exterior member As the exterior member, a laminate film having a thickness of 0.5 mm or less or a metal container having a thickness of 3 mm or less is used. The metal container is more preferably 0.5 mm or less in thickness. A resin container made of polyolefin resin, polyvinyl chloride resin, polystyrene resin, acrylic resin, phenol resin, polyphenylene resin, fluorine resin, or the like may be used.

  Examples of the shape of the exterior member, that is, the battery shape, include a flat type (thin type), a square type, a cylindrical type, a coin type, and a button type. In addition, the battery can be applied to, for example, a small-sized application loaded on a portable electronic device or the like, and a large-sized application loaded on a two-wheel to four-wheeled vehicle or the like.

  As the laminate film, a multilayer film in which a metal layer is interposed between resin layers is used. The metal layer is preferably an aluminum foil or an aluminum alloy foil for weight reduction. For the resin layer, for example, a polymer material such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used. The laminate film can be formed into the shape of an exterior member by sealing by heat sealing.

  The metal container is made of aluminum or an aluminum alloy. As the aluminum alloy, an alloy containing elements such as magnesium, zinc and silicon is preferable. When transition metals such as iron, copper, nickel and chromium are contained in the alloy, the amount is preferably 100 ppm or less.

6) Negative electrode terminal The negative electrode terminal can be formed from aluminum or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, or Si. In order to reduce the contact resistance with the negative electrode current collector, the negative electrode terminal is preferably formed from the same material as the negative electrode current collector.

7) Positive electrode terminal The positive electrode terminal may be formed of aluminum or an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, or Si. preferable. In order to reduce the contact resistance with the positive electrode current collector, the positive electrode terminal is preferably formed of the same material as the positive electrode current collector.

  Next, an example of the nonaqueous electrolyte battery according to the first embodiment will be described in detail with reference to the drawings.

  FIG. 1 is an exploded perspective view of an example nonaqueous electrolyte battery according to the first embodiment. FIG. 2 is a partially developed perspective view of an electrode group included in the nonaqueous electrolyte battery shown in FIG.

  A battery 100 shown in FIG. 1 is a sealed rectangular nonaqueous electrolyte battery. The nonaqueous electrolyte battery 100 includes an outer can 1, a lid 2, a positive external terminal 3, a negative external terminal 4, and an electrode group 5. The outer can 1 and the lid 2 constitute an outer member.

  The outer can 1 has a bottomed rectangular tube shape, and is formed of a metal such as aluminum, an aluminum alloy, iron, or stainless steel, for example.

  As shown in FIG. 2, the flat electrode group 5 has a positive electrode 6 and a negative electrode 7 wound in a flat shape with a separator 8 therebetween. The positive electrode 6 is a positive electrode except for, for example, a strip-shaped positive electrode current collector made of a metal foil, a positive electrode current collector tab 6a having one end parallel to the long side of the positive electrode current collector, and at least the positive electrode current collector tab 6a. And a positive electrode material layer (positive electrode active material-containing layer) 6b formed on the current collector. On the other hand, the negative electrode 7 excludes, for example, a strip-shaped negative electrode current collector made of a metal foil, a negative electrode current collector tab 7a having one end parallel to the long side of the negative electrode current collector, and at least a portion of the negative electrode current collector tab 7a. And a negative electrode material layer (negative electrode active material-containing layer) 7b formed on the negative electrode current collector.

  In such a positive electrode 6, separator 8 and negative electrode 7, the positive electrode current collecting tab 6 a protrudes from the separator 8 in the winding axis direction of the electrode group 5, and the negative electrode current collecting tab 7 a protrudes from the separator 8 in the opposite direction. Thus, the positions of the positive electrode 6 and the negative electrode 7 are wound while being shifted. As a result of such winding, as shown in FIG. 2, the electrode group 5 has the positive electrode current collecting tab 6a wound in a spiral shape from one end face and is wound in a spiral form from the other end face. The negative electrode current collection tab 7a protrudes. An electrolytic solution (not shown) is impregnated in the electrode group 5.

  As shown in FIG. 1, the positive electrode tab 6a and the negative electrode tab 7a are each divided into two bundles with the vicinity of the winding center of the electrode group 5 as a boundary, and each of the two conductive holding members 9 It is pinched. The sandwiching member 9 includes a first sandwiching portion 9a and a second sandwiching portion 9b that are substantially U-shaped, and a connecting portion that electrically connects the first sandwiching portion 9a and the second sandwiching portion 9b. 9c. One bundle of the positive electrode tabs 6a is held by the first holding part 9a of one holding member 9, and the other bundle of the positive electrode tabs 6a is held by the second holding part 9b of the same holding member 9. ing. Similarly, one bundle of the negative electrode tabs 7a is held by the first holding part 9a of the other holding member 9, and the other bundle of the negative electrode tabs 7a is the second holding part of the same holding member 9. 9b.

  The positive electrode lead 10 includes a substantially rectangular support plate 10a, a through hole 10b opened in the support plate 10a, a bifurcated bifurcated branch from the support plate 10a, and strip-shaped current collectors 10c and 10d extending downward. Have On the other hand, the negative electrode lead 11 includes a substantially rectangular support plate 11a, a through hole 11b opened in the support plate 11a, a bifurcated branch from the support plate 11a, and a strip-shaped current collector 11c extending downward. 11d.

  The current collectors 10c and 10d of the positive electrode lead 10 sandwich one clamping member 9 therebetween. The current collector 10 c is disposed in the first clamping part 9 a of the clamping member 9. The current collector 10d is disposed in the second clamping unit 9b. The current collectors 10c and 10d, the first and second sandwiching parts 9a and 9b, and the positive electrode current collector tab 6a are joined by, for example, ultrasonic welding. Thereby, the positive electrode 6 and the positive electrode lead 10 of the electrode group 5 are electrically connected via the positive electrode current collection tab 6a.

  Another collector 9 is sandwiched between the current collectors 11 c and 11 d of the negative electrode lead 11. The current collector 11 c is disposed in the first clamping part 9 a of the clamping member 9. On the other hand, the current collection part 11d is arrange | positioned at the 2nd clamping part 9b. The current collecting parts 11c and 11d, the first and second clamping parts 9a and 9b, and the negative electrode current collecting tab 7a are joined by, for example, ultrasonic welding. Thereby, the negative electrode 7 and the negative electrode lead 11 of the electrode group 5 are electrically connected via the negative electrode current collection tab 7a.

  The materials of the positive electrode lead 10, the negative electrode lead 11, and the sandwiching member 9 are not particularly specified, but are preferably the same material as the positive electrode external terminal 3 and the negative electrode external terminal 4. For the positive electrode external terminal 3, for example, aluminum or an aluminum alloy is used, and for the negative electrode external terminal 4, for example, aluminum, an aluminum alloy, copper, nickel, nickel-plated iron, or the like is used. For example, when the material of the external terminal is aluminum or an aluminum alloy, the lead material is preferably aluminum or an aluminum alloy. In addition, when the external terminal is copper, it is desirable that the material of the lead is copper.

  The rectangular plate-shaped lid 2 is seam welded to the opening of the outer can 1 by, for example, a laser. The lid 2 is made of a metal such as aluminum, aluminum alloy, iron or stainless steel, for example. The lid 2 and the outer can 1 are preferably formed from the same type of metal. The positive external terminal 3 is electrically connected to the support plate 10 a of the positive electrode lead 10, and the negative external terminal 4 is electrically connected to the support plate 11 a of the negative electrode lead 11. Insulating gaskets 12 are disposed between the positive external terminal 3 and the lid 2 and between the negative external terminal 4 and the lid 2, respectively. The positive external terminal 3, the negative external terminal 4, and the lid 2 are connected to each other. It is electrically insulated. The insulating gasket 12 is preferably a resin molded product.

According to the first embodiment, a nonaqueous electrolyte battery is provided. In this non-aqueous electrolyte battery, the negative electrode has a Li storage potential of 1 V vs. The negative electrode active material which is more than Li / Li ⁺ is included. Moreover, the electrical resistance in the discharge state of a negative electrode exists in the range of 100 ohm * cm-100000 ohm * cm. Further, the separator has a pore volume ratio of pores having a pore diameter of 1 μm or more of greater than 70%. This nonaqueous electrolyte battery can prevent clogging of the separator and prevent self-discharge. As a result, this non-aqueous electrolyte battery can exhibit excellent life characteristics and suppress self-discharge.

(Second Embodiment)
According to the second embodiment, a battery pack is provided. This battery pack includes the nonaqueous electrolyte battery according to the first embodiment.

  The battery pack according to the second embodiment may include one nonaqueous electrolyte battery or a plurality of nonaqueous electrolyte batteries. Further, when the battery pack according to the second embodiment includes a plurality of nonaqueous electrolyte batteries, each single cell can be electrically connected in series or in parallel, and can be connected in series and parallel. It can also be arranged in combination.

  Next, an example of the battery pack according to the second embodiment will be described with reference to the drawings.

  FIG. 3 is an exploded perspective view of an example battery pack according to the second embodiment. FIG. 4 is a block diagram showing an electric circuit of the battery pack shown in FIG.

  The battery pack 200 shown in FIGS. 3 and 4 includes a plurality of flat batteries 100 having the structure shown in FIGS. 1 and 2.

  The plurality of single cells 100 are laminated so that the negative electrode external terminal 4 and the positive electrode external terminal 3 extending to the outside are aligned in the same direction, and are fastened with an adhesive tape 22, thereby forming an assembled battery 23. ing. These unit cells 100 are electrically connected to each other in series as shown in FIG.

  The printed wiring board 24 is disposed so as to face the side surface where the negative electrode external terminals 4 and the positive electrode external terminals 3 of the plurality of single cells 100 extend. As shown in FIG. 4, a thermistor 25, a protection circuit 26, and a terminal 27 for energizing external devices are mounted on the printed wiring board 24. An insulating plate (not shown) is attached to the surface of the printed wiring board 24 facing the assembled battery 23 in order to avoid unnecessary connection with the wiring of the assembled battery 23.

  A positive electrode side lead 28 is connected to the positive electrode external terminal 3 of the unit cell 100 located in the lowermost layer of the assembled battery 23, and the tip thereof is inserted into the positive electrode side connector 29 of the printed wiring board 24 and electrically connected thereto. Yes. A negative electrode side lead 30 is connected to the negative electrode external terminal 4 of the unit cell 100 located in the uppermost layer of the assembled battery 23, and the tip thereof is inserted into and electrically connected to the negative electrode side connector 31 of the printed wiring board 24. Yes. These connectors 29 and 31 are connected to the protection circuit 26 through wirings 32 and 33 formed on the printed wiring board 24, respectively.

  The thermistor 25 detects the temperature of each of the unit cells 100 and transmits the detection signal to the protection circuit 26. The protection circuit 26 can cut off the plus side wiring 34a and the minus side wiring 34b between the protection circuit 26 and the energization terminal 27 to the external device under a predetermined condition. An example of the predetermined condition is when, for example, a signal is received from the thermistor 25 that the temperature of the unit cell 100 is equal to or higher than the predetermined temperature. Another example of the predetermined condition is when an overcharge, overdischarge, overcurrent, or the like of the unit cell 100 is detected. This detection of overcharge or the like is performed for each single cell 100 or the entire single cell 100. When detecting each single battery 100, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 100. In the battery pack 200 of FIG. 3 and FIG. 4, a wiring 35 for voltage detection is connected to each single cell 100, and a detection signal is transmitted to the protection circuit 26 through these wirings 35.

  Protective sheets 36 made of rubber or resin are disposed on the three side surfaces of the assembled battery 23 excluding the side surface from which the positive electrode external terminal 3 and the negative electrode external terminal 4 protrude.

  The assembled battery 23 is stored in a storage container 37 together with the protective sheets 36 and the printed wiring board 24. That is, the protective sheet 36 is disposed on both the inner side surface in the long side direction and the inner side surface in the short side direction of the storage container 37, and the printed wiring board 24 is disposed on the inner side surface on the opposite side in the short side direction. Yes. The assembled battery 23 is located in a space surrounded by the protective sheet 36 and the printed wiring board 24. The lid 38 is attached to the upper surface of the storage container 37.

  In addition, instead of the adhesive tape 22, a heat shrink tape may be used for fixing the assembled battery 23. In this case, protective sheets are arranged on both side surfaces of the assembled battery, the heat shrinkable tube is circulated, and then the heat shrinkable tube is thermally contracted to bind the assembled battery.

  The battery pack 200 shown in FIGS. 3 and 4 has a configuration in which a plurality of unit cells 100 are connected in series. However, the battery pack according to the second embodiment has a plurality of unit cells 100 in order to increase the battery capacity. May be connected in parallel. Alternatively, the battery pack according to the second embodiment may include a plurality of single cells 100 connected in combination of series connection and parallel connection. The assembled battery pack 200 can be further connected in series or in parallel.

  3 and 4 includes a plurality of unit cells 100, the battery pack according to the second embodiment may include one unit cell 100.

  Further, the embodiment of the battery pack is appropriately changed depending on the application. The battery pack according to the present embodiment is suitably used for applications that require excellent cycle characteristics when a large current is taken out. Specifically, it is used as a power source for a digital camera, or as an in-vehicle battery for, for example, a two-wheel to four-wheel hybrid electric vehicle, a two-wheel to four-wheel electric vehicle, and an assist bicycle. In particular, it is suitably used as a vehicle-mounted battery.

  The battery pack according to the second embodiment includes the nonaqueous electrolyte battery according to the first embodiment. Thanks to this, the battery pack according to the second embodiment can exhibit excellent life characteristics and suppress self-discharge.

[Example]
Examples will be described below, but the present invention is not limited to the examples described below as long as the gist of the present invention is not exceeded.

Example 1
In Example 1, the nonaqueous electrolyte battery 100 having the structure shown in FIGS. 1 and 2 was produced by the following procedure.

<Preparation of positive electrode 6>
LiNi _0.5 Co _0.2 Mn _0.3 O ₂ was prepared as a positive electrode active material. In addition, graphite and acetylene black were prepared as conductive agents. Then, polyvinylidene fluoride (PVdF) was prepared as a binder. Next, a positive electrode active material, graphite, acetylene black, and PVdF were mixed to obtain a mixture. At this time, the graphite was added in a proportion of 2.5% by weight with respect to the entire positive electrode to be produced. Acetylene black was added at a ratio of 2.5% by weight based on the whole positive electrode to be produced. PVdF was added so that it might become 5 weight% with respect to the whole positive electrode to produce. Next, the obtained mixture was dispersed in an n-methylpyrrolidone (NMP) solvent to prepare a slurry. The obtained slurry was applied to an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 80 g / m ² and dried. Next, the dried coating film was pressed. Thus, a positive electrode 6 having an electrode density of 3.0 g / cm ³ was produced.

<Preparation of negative electrode 7>
As a negative electrode active material, Li occlusion potential is 1.4 V to 2.0 V vs. A spinel type lithium titanium composite oxide Li ₄ Ti ₅ O ₁₂ having a range of Li / Li ⁺ and a specific surface area of 10 m ² / g was prepared. Moreover, the graphite whose specific surface area is 18 m < ² > / g was prepared as a electrically conductive agent. And PVdF was prepared as a binder. Next, the negative electrode active material, graphite, and PVdF were mixed to obtain a mixture. At this time, graphite was added so as to be 5% by weight with respect to the whole negative electrode to be produced. PVdF was added so that it might become 5 weight% with respect to the whole negative electrode to produce. Next, a slurry was prepared by mixing the obtained mixture in an N-methylpyrrolidone (NMP) solution. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 120 g / m ² and dried. Next, the dried coating film was pressed to form a negative electrode material layer on the current collector. Thus, a strip-shaped negative electrode 7 having an electrode density of 2.1 g / cm ³ was produced.

In the negative electrode 7, the specific surface area A of the spinel type lithium titanium composite oxide is 10 m ² / g, the weight content ratio B of the spinel type lithium titanium composite oxide is 90, and the specific surface area C of graphite is 18 m ² / g. And the weight content ratio D of graphite was 5. That is, the negative electrode 7 of Example 1 had an AB / CD value of 10.

<Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte was prepared by mixing and dissolving 1.0 M LiPF ₆ in a non-aqueous solvent consisting of 33% by volume propylene carbonate (PC) and 67% by volume dimethyl carbonate (DMC).

<Battery assembly>
A separator 8 made of a cellulose nonwoven fabric having a thickness of 20 μm was prepared.

  This separator 8 was impregnated with the previously prepared nonaqueous electrolyte. Next, the positive electrode 6 previously produced was covered with the separator 8, and then the negative electrode 7 produced previously was overlapped with the positive electrode 6 through the separator 8 to obtain a laminate. This laminated body was wound in a spiral shape to produce a spiral electrode group 5. This electrode group 5 was subjected to pressing and formed into a flat shape as shown in FIG.

  The flat electrode group 5 was inserted into a can-shaped container 1 made of aluminum having a thickness of 0.3 mm and sealed with a lid 2. In this way, a flat nonaqueous electrolyte battery 100 having a thickness of 5 mm, a width of 30 mm, a height of 25 mm, and a weight of 100 g shown in FIGS. 1 and 2 was produced.

<Measurement of battery capacity>
The obtained battery was charged at a constant current until the battery voltage reached 2.8 V at 20 mA in a 25 ° C. environment, and then charged at a constant voltage until the charging current reached 5 mA. Subsequently, when the battery capacity was confirmed by discharging until the battery voltage reached 1.5 V at 20 mA, the obtained battery capacity was 250 mAh.

<Evaluation of life characteristics>
The obtained battery was adjusted so that the battery voltage was 2.0 V in a 25 ° C. environment, and then the resistance value at 1 kHz was measured. Subsequently, a cycle test of charging the obtained battery at 2.6 V with a current value of 5 C at a current value of 5 C and discharging 1.8 V at a current value of 5 C in a 60 ° C. environment was performed 50000 times, and the environmental temperature was 25. After returning to ° C., the battery voltage was adjusted to 2.0 V, and then the resistance value at 1 kHz was measured.

<Self-discharge evaluation>
The obtained battery was discharged at 20 mA in a 25 ° C. environment until the battery voltage reached 1.5 V, and then charged at 20 mA to half the battery capacity, that is, the battery capacity was 125 mAh. The obtained battery was allowed to stand for 2 weeks in a −20 ° C. environment, and after returning the environmental temperature to 25 ° C., the battery capacity was measured when the battery was discharged at 20 mA until the battery voltage reached 1.5V. The amount of self-discharge was calculated by subtracting the battery capacity obtained from the half charge capacity.

<Electric resistance in the discharge state of the negative electrode>
The electrical resistance in the discharge state of the negative electrode 7 included in the nonaqueous electrolyte battery 100 of Example 1 was measured by the method described above. The electrical resistance of the negative electrode 7 in the discharged state was 8000 Ω · cm.

<Measurement of pore diameter distribution of separator 8>
The pore diameter distribution measurement of the separator 8 included in the nonaqueous electrolyte battery 100 of Example 1 was performed by the mercury intrusion method as described above. The integrated pore volume frequency curve obtained as a result of this pore diameter distribution measurement is shown in FIG. 5, and the pore diameter distribution curve is shown in FIG. 5 and 6 are semilogarithmic graphs in which the horizontal axis is the logarithm of the pore diameter (μm).

  From the cumulative pore volume frequency curve shown in FIG. 5, the separator 8 included in the nonaqueous electrolyte battery 100 of Example 1 has a pore volume ratio of 78% of pores having a pore diameter of 1 μm or more. I understood. Further, from the pore diameter distribution curve shown in FIG. 6, it was found that the mode diameter of the separator 8 was 2.6 μm.

(Example 2)
In Example 2, the Li storage potential is 1.2 V to 2.0 V vs. A battery was prepared in the same manner as in Example 1 except that bronze-type titanium dioxide TiO ₂ (B) in the range of Li / Li ⁺ was used as the negative electrode active material. The weight content ratio of TiO ₂ (B) in the negative electrode 7 was the same as in Example 1.

(Example 3)
In Example 3, the Li storage potential is 1.0 V to 2.0 V vs. A battery was produced in the same manner as in Example 1 except that monoclinic niobium titanium oxide Nb ₂ TiO ₇ within the range of Li / Li ⁺ was used as the negative electrode active material. Weight content ratio of Nb ₂ TiO ₇ in the negative electrode 7 was the same as that of Example 1.

(Examples 4 and 5)
In Examples 4 and 5, non-aqueous electrolyte batteries were produced in the same manner as in Example 1 except that the separator was changed.

(Example 6)
In Example 6, a nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the negative electrode produced as described below was used.

As a negative electrode active material, Li occlusion potential is 1.4 V to 2.0 V vs. A spinel-type lithium-titanium composite oxide Li ₄ Ti ₅ O ₁₂ having a surface area of Li / Li ⁺ or higher and a specific surface area of 10 m ² / g was prepared. Moreover, the graphite whose specific surface area is 18 m < ² > / g was prepared as a electrically conductive agent. And PVdF was prepared as a binder. Next, the negative electrode active material, graphite, and PVdF were mixed to obtain a mixture. At this time, graphite was added so as to be 2.85% by weight with respect to the whole negative electrode to be produced. PVdF was added so that it might become 5 weight% with respect to the whole negative electrode to produce. Next, a slurry was prepared by mixing the obtained mixture in an N-methylpyrrolidone (NMP) solution. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 155 g / m ² and dried. Next, the dried coating film was pressed to form a negative electrode material layer on the current collector. Thus, a strip-shaped negative electrode having an electrode density of 2.1 g / cm ³ was produced.

In the negative electrode 7, the specific surface area A of the spinel-type lithium-titanium composite oxide is 10 m ² / g, the weight content ratio B of the spinel-type lithium-titanium composite oxide is 92.15, the specific surface area of graphite 18m ² / g, and the weight content ratio D of graphite was 2.85. That is, the negative electrode 7 of Example 6 had an AB / CD value of 18.

(Example 7)
In Example 7, a nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the negative electrode produced as described below was used.

As a negative electrode active material, Li occlusion potential is 1.4 V to 2.0 V vs. A spinel-type lithium-titanium composite oxide Li ₄ Ti ₅ O ₁₂ having a surface area of Li / Li ⁺ or higher and a specific surface area of 10 m ² / g was prepared. Moreover, the graphite whose specific surface area is 18 m < ² > / g was prepared as a electrically conductive agent. And PVdF was prepared as a binder. Next, the negative electrode active material, graphite, and PVdF were mixed to obtain a mixture. At this time, graphite was added so as to be 9.5% by weight with respect to the entire negative electrode to be produced. PVdF was added so that it might become 5 weight% with respect to the whole negative electrode to produce. Next, a slurry was prepared by mixing the obtained mixture in an N-methylpyrrolidone (NMP) solution. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 155 g / m ² and dried. Next, the dried coating film was pressed to form a negative electrode material layer on the current collector. Thus, a strip-shaped negative electrode having an electrode density of 2.1 g / cm ³ was produced.

In the negative electrode 7, the specific surface area A of the spinel-type lithium-titanium composite oxide is 10 m ² / g, the weight content ratio B of the spinel-type lithium-titanium composite oxide is 85.5, the specific surface area of graphite 18m ² / g, and the weight content ratio D of graphite was 9.5. That is, the negative electrode 7 of Example 7 had an AB / CD value of 5.

(Examples 8 to 10)
In Examples 8 to 10, non-aqueous electrolyte batteries were produced in the same manner as in Example 1 except that the separator was changed.

(Comparative Example A)
In Comparative Example A, a nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the separator was changed.

(Comparative Example B)
In Comparative Example B, a nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the negative electrode produced as described below was used.

As a negative electrode active material, Li occlusion potential is 1.4 V to 2.0 V vs. A spinel type lithium titanium composite oxide Li ₄ Ti ₅ O ₁₂ having a range of Li / Li ⁺ and a specific surface area of 10 m ² / g was prepared. Moreover, the graphite whose specific surface area is 18 m < ² > / g was prepared as a electrically conductive agent. And PVdF was prepared as a binder. Next, the negative electrode active material, graphite, and PVdF were mixed to obtain a mixture. At this time, the graphite was added so as to be 15% by weight with respect to the entire negative electrode to be produced. PVdF was added so that it might become 5 weight% with respect to the whole negative electrode to produce. Next, a slurry was prepared by mixing the obtained mixture in an N-methylpyrrolidone (NMP) solution. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 155 g / m ² and dried. Next, the dried coating film was pressed to form a negative electrode material layer on the current collector. Thus, a strip-shaped negative electrode having an electrode density of 2.1 g / cm ³ was produced.

In the negative electrode 7, the specific surface area A of the spinel type lithium titanium composite oxide is 10 m ² / g, the weight content ratio B of the spinel type lithium titanium composite oxide is 80, and the specific surface area of graphite is 18 m ² / g. Yes, the weight content ratio D of the graphite was 15. That is, the negative electrode 7 of Comparative Example B had an AB / CD value of 3.

(Comparative Example C)
In Comparative Example C, a nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the negative electrode produced as described below was used.

As the negative electrode active material, the Li occlusion potential is 1.4 V to 2.0 V vs. Li occlusion potential. A lithium titanium composite oxide Li ₄ Ti ₅ O ₁₂ having a range of Li / Li ⁺ and a specific surface area of 10 m ² / g was prepared. Moreover, PVdF was prepared as a binder. Next, the negative electrode active material and PVdF were mixed to obtain a mixture. At this time, PVdF was added so as to be 5% by weight with respect to the entire negative electrode to be produced. Next, a slurry was prepared by mixing the obtained mixture in an N-methylpyrrolidone (NMP) solution. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 130 g / m ² and dried. Next, the dried coating film was pressed to form a negative electrode material layer on the current collector. Thus, a strip-shaped negative electrode having an electrode density of 2.1 g / cm ³ was produced.

  That is, the negative electrode of the nonaqueous electrolyte battery of Comparative Example C did not contain a conductive agent.

(Comparative Example D)
In Comparative Example D, a nonaqueous electrolyte battery was produced in the same manner as in Example 1 except that the negative electrode produced as described below was used.

As a negative electrode active material, Li occlusion potential is 0.01 V to 0.9 V vs. A graphite in the range of Li / Li ⁺ was prepared. Moreover, PVdF was prepared as a binder. Next, the negative electrode active material (graphite) and PVdF were mixed to obtain a mixture. At this time, PVdF was added so as to be 5% by weight based on the whole negative electrode to be produced. Next, a slurry was prepared by mixing the obtained mixture in an N-methylpyrrolidone (NMP) solution. The obtained slurry was applied to a current collector made of an aluminum foil having a thickness of 15 μm so that the coating amount per unit area was 60 g / m ² and dried. Next, the dried coating film was pressed to form a negative electrode material layer on the current collector. Thus, a strip-shaped negative electrode 7 having an electrode density of 1.5 g / cm ³ was produced.

  The obtained battery was charged at a constant current until the battery voltage reached 4.2 V at 20 mA in a 25 ° C. environment, and then charged at a constant voltage until the charging current reached 5 mA. Subsequently, discharging was performed at 20 mA until the battery voltage reached 3.0 V, and the battery capacity was confirmed. The obtained battery capacity was 250 mAh.

(Comparative Examples E and F)
In Comparative Examples E and F, nonaqueous electrolyte batteries were produced in the same manner as in Examples 2 and 3 except that the separator was changed.

For the nonaqueous electrolyte batteries of Examples 2 to 10 and Comparative Examples A to F, as in Example 1, evaluation of life characteristics, self-discharge evaluation, measurement of resistance in the discharge state of the negative electrode, and pore diameter distribution of the separator Was measured. The results are shown in Table 1 and Table 2 below together with the results of Example 1.

  From the results shown in Table 1, the nonaqueous electrolyte batteries 100 of Examples 1 to 10 were able to exhibit a low resistance value before the cycle, and to suppress the self-discharge due to storage and the increase in resistance due to the cycle. I understand.

Comparing the results of Examples 1 to 3 in which the negative electrode active material used was different, even if the negative electrode active material was different, the Li storage potential of the negative electrode active material was 1 V vs. It can be seen that if Li / Li ⁺ or higher, self-discharge due to storage and resistance increase due to cycling could be similarly suppressed.

On the other hand, the Li storage potential is 1 V vs. In Comparative Example D using graphite that is less than Li / Li ⁺ as the negative electrode active material, the self-discharge due to storage and the increase in resistance due to cycling were significantly greater than in Examples 1-3. In Comparative Example D, this is probably due to the low resistance of the negative electrode in the discharge state and the deposition of lithium on the negative electrode due to the cycle.

  Moreover, when the results of Examples 1, 4, 5, and 8 to 10 and Comparative Example A, which are different only in the separator used, are compared, Comparative Example A is the same as Examples 1, 4, 5, and 8 to 10. It can be seen that although the self-discharge can be suppressed, the increase in the resistance value due to the cycle is significantly larger than those of these examples. In Comparative Example A, the pore volume ratio of pores having a pore diameter of 1 μm or more was less than 70%, which is considered to be caused by clogging of the separator pores due to the cycle. It is done. Furthermore, from the comparison between the result of Example 2 and the result of Comparative Example E, and the comparison of the result of Example 3 and the result of Comparative Example F, the same tendency should be confirmed even if the type of the negative electrode active material is different. I was able to.

  From comparison of the results of Examples 1, 6 and 7 in which the discharge state resistance of the negative electrode is different, these examples in which the discharge state resistance of the negative electrode is in the range of 100 Ω · cm to 100000 Ω · cm are self-discharged by storage. It can also be seen that the increase in resistance due to the cycle could be similarly suppressed.

  On the other hand, Comparative Example B, in which the resistance of the negative electrode in the discharged state was less than 100 Ω · cm, had a significantly larger amount of self-discharge during storage than Examples 1, 6 and 7. This is because in Comparative Example B, since the resistance of the negative electrode in the discharge state was too low, the self-discharge reaction that occurred when the positive electrode and the negative electrode contacted each other at the through-hole portion of the separator had progressed. it is conceivable that.

  Moreover, the resistance value of the comparative example C in which the resistance of the negative electrode in the discharge state was higher than 100,000 Ω · cm was significantly higher than those of Examples 1, 6, and 7. This is considered to be because Comparative Example C had a too high resistance in the discharge state of the negative electrode. The battery of Comparative Example C was remarkably inferior in output characteristics due to such high resistance.

In the non-aqueous electrolyte battery according to at least one embodiment and example described above, the negative electrode has a Li storage potential of 1 V vs. The negative electrode active material which is more than Li / Li ⁺ is included. Moreover, the electrical resistance in the discharge state of a negative electrode exists in the range of 100 ohm * cm-100000 ohm * cm. Further, the separator has a pore volume ratio of pores having a pore diameter of 1 μm or more of greater than 70%. This nonaqueous electrolyte battery can prevent clogging of the separator and prevent self-discharge. As a result, this non-aqueous electrolyte battery can exhibit excellent life characteristics and suppress self-discharge.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
The invention described in the scope of the claims at the beginning of the filing of the original application is added below.
[1] In a nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and a nonaqueous electrolyte, the negative electrode has a Li storage potential of 1 V vs. It includes a negative electrode active material that is Li / Li ⁺ or more, has an electric resistance in a discharged state within a range of 100 Ω · cm to 100,000 Ω · cm, and is obtained from an integrated pore volume frequency curve obtained by a mercury intrusion method of the separator. A nonaqueous electrolyte battery, wherein a pore volume ratio of pores having a pore diameter of 1 μm or more is greater than 70%.
[2] The nonaqueous electrolyte battery according to [1], wherein a mode diameter in a pore diameter distribution curve obtained by a mercury intrusion method of the separator is in a range of 1 to 20 μm.
[3] The nonaqueous electrolyte battery according to [2], wherein the separator has a thickness in the range of 3 to 25 μm.
[4] The nonaqueous electrolyte battery according to [2], wherein the negative electrode active material contains Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3).
[5] A battery pack comprising the nonaqueous electrolyte battery according to [1].

  DESCRIPTION OF SYMBOLS 100 ... Nonaqueous electrolyte battery, 1 ... Exterior can, 2 ... Cover body, 3 ... Positive electrode external terminal, 4 ... Negative electrode external terminal, 5 ... Electrode group, 6 ... Positive electrode, 6a ... Positive electrode current collection tab, 6b ... Positive electrode material layer (Positive electrode active material containing layer), 7 ... negative electrode, 7a ... negative electrode current collecting tab, 7b ... negative electrode material layer (negative electrode active material containing layer), 8 ... separator, 9 ... clamping member, 9a ... first clamping part, 9b 2nd clamping part, 9c ... Connecting part, 10 ... Positive electrode lead, 10a ... Support plate, 10b ... Through hole, 10c and 10d ... Current collecting part, 11 ... Negative electrode lead, 11a ... Support plate, 11b ... Through hole, 11c and 11d ... current collector, 12 ... insulating gasket, 200 ... battery pack, 22 ... adhesive tape, 23 ... assembled battery, 24 ... printed circuit board, 25 ... thermistor, 26 ... protection circuit, 27 ... terminal for energization, 28 ... positive electrode side lead, 29 ... positive electrode side connector, 30 ... negative Side lead, 31 ... negative electrode side connector, 32 and 33 ... wiring, 34a ... positive-side wiring, 34b ... minus side wiring, 35 ... wiring for voltage detection, 36 ... protection sheet, 37 ... container, 38 ... lid.

Claims (5)

In a nonaqueous electrolyte battery comprising a positive electrode, a negative electrode, a separator interposed between them and a nonaqueous electrolyte,
The negative electrode has a Li storage potential of 1 V vs. Including a negative electrode active material that is greater than or equal to Li / Li ⁺ , and the electrical resistance of the negative electrode in a discharged state is in the range of 100 Ω · cm to 100,000 Ω · cm,
The pore volume ratio of pores having a pore diameter of 1 μm or more determined from an integrated pore volume frequency curve obtained from the mercury intrusion method of the separator is greater than 70%,
A nonaqueous electrolyte battery in which a pore diameter distribution curve obtained by a mercury intrusion method of the separator has a mode diameter in a range of 1.1 to 7.8 μm.   The nonaqueous electrolyte battery according to claim 1, wherein the mode diameter is in a range of 2.6 to 7.8 μm.   The nonaqueous electrolyte battery according to claim 1, wherein the separator has a thickness in the range of 3 to 25 μm. The non-aqueous electrolyte battery according to claim 1, wherein the negative electrode active material contains Li _{4 + x} Ti ₅ O ₁₂ (0 ≦ x ≦ 3).   The battery pack containing the nonaqueous electrolyte battery of any one of Claims 1-4.