Non-aqueous electrolyte battery and battery pack

Abstract

According to an embodiment of the present invention, provided is a non-aqueous electrolyte battery comprising: a positive electrode; a negative electrode; a separator provided between the positive electrode and the negative electrode; and a non-aqueous electrolyte. The separator includes nonwoven fabric. In each of the main faces on both the front and back sides of the separator and the region of a one-third portion at the center of the separator in the thickness direction, the mass ratio of fluorine is 10%-20%, and the mass ratio of phosphorus is 4%-10%. The air permeability of the nonwoven fabric is 30 seconds / 100 cm3 to 50 seconds / 100 cm3.

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] In recent years, with the widespread use of electric vehicles (EVs) and electric buses (EV buses), there has been a demand for longer driving distances per charge. For the lithium-ion batteries that power these vehicles, there is a strong demand for high-energy-density lithium-ion batteries from the viewpoint of increasing the charging capacity per pack while reducing weight. One way to achieve this high energy density is to increase the battery capacity.

[0003] However, as battery capacity increases, battery safety decreases. In other words, there is a trade-off between capacity and safety in batteries. For example, a separator that prevents electrical contact between the positive and negative electrodes has a coarser mesh, which increases the transport of charge carrier ions between the positive and negative electrodes, thereby lowering battery resistance and improving capacity and input / output performance. However, a coarser mesh separator has greater in-plane thermal shrinkage, resulting in lower safety. Conversely, a denser separator has less thermal shrinkage and lower ion transport. To ensure battery safety, attempts have been made to apply inorganic fillers to separators. However, because inorganic fillers are insulators, the more they are applied, the lower the battery's output performance.

[0004] JP 2017-76484 A International Publication No. 2021 / 131533

[0005] To provide a non-aqueous electrolyte battery and a battery pack that achieve both high output performance and high safety.

[0006] According to an embodiment, a non-aqueous electrolyte battery is provided, which includes a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode and including a nonwoven fabric, and a non-aqueous electrolyte. The separator has a fluorine mass ratio of 10% to 20% and a phosphorus mass ratio of 4% to 10% on both the front and back main surfaces and in a central one-third region in the thickness direction of the separator. The non-woven fabric has an air permeability of 30 seconds / 100 cm. ３ More than 50 seconds / 100cm ３ The following is the result.

[0007] According to another embodiment, a battery pack is provided, which includes a nonaqueous electrolyte battery according to the embodiment.

[0008] Fig. 1 is an exploded perspective view of an example of a nonaqueous electrolyte battery according to an embodiment. Fig. 2 is a partially exploded perspective view of an example of an electrode group used in the nonaqueous electrolyte battery shown in Fig. 1. Fig. 3 is a block diagram showing an example of an electric circuit of a battery pack according to an embodiment. Embodiment

[0009] First Embodiment A nonaqueous electrolyte battery is provided according to a first embodiment. The nonaqueous electrolyte battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte.

[0010] The separator is disposed between the positive electrode and the negative electrode. The separator includes a nonwoven fabric. The separator includes a compound containing fluorine and phosphorus on both its front and back main surfaces and in a central one-third region in the thickness direction within the separator. The fluorine mass ratio on both main surfaces and in the central region is 10% or more and 20% or less. The phosphorus mass ratio on both main surfaces and in the central region is 4% or more and 10% or less. Because fluorine compounds and phosphorus compounds have high heat resistance, a separator having a fluorine mass ratio of 10% or more and a phosphorus mass ratio of 4% or more in each region has a small in-plane thermal shrinkage rate. Therefore, the use of such a separator can provide high safety. Fluorine compounds and phosphorus compounds are also insulating materials. A separator having a fluorine mass ratio of 20% or less and a phosphorus mass ratio of 10% or less in each region does not impede the transport of charge carrier ions, and therefore the use of such a separator can provide good output performance. Therefore, a battery having a separator containing fluorine and phosphorus in a mass ratio within the above range exhibits high output performance and is highly safe.

[0011] The fluorine-containing compound and the phosphorus-containing compound may have, for example, a particulate form. A specific example of a particulate fluorine compound is lithium fluoride (LiF) particles. The particulate fluorine compound and phosphorus compound are contained on the surface of the separator and inside the separator in a form entangled with the fibers of the nonwoven fabric contained in the separator. By containing the fluorine compound and phosphorus compound on both surfaces and inside the separator, the thermal shrinkage rate in the in-plane direction of the nonwoven fabric separator is reduced. For example, even if the fluorine compound and phosphorus compound are present on only one side of the separator, the thermal shrinkage of the separator will not be reduced. However, in order to avoid impeding the transport of charge carrier ions, it is desirable that the fluorine compound and phosphorus compound are not in the form of a coating or layer covering the separator surface (nonwoven fabric surface).

[0012] The front and back principal surfaces of the separator as used herein refer to the front and back principal surfaces of the nonwoven fabric contained in the separator. Furthermore, the central one-third region in the thickness direction of the separator refers to the middle portion when a cross section intersecting the main surface of the nonwoven fabric is divided into three equal parts in the thickness direction, with the thickness of the nonwoven fabric being the thickness of the separator. The fluorine mass ratio and phosphorus mass ratio can be within the above-described ranges not only in the central region in the thickness direction but also throughout the entire thickness direction of the nonwoven fabric. In other words, such a separator can be in a state in which the fluorine compound and the phosphorus compound are dispersed throughout the entire nonwoven fabric, from one principal surface side to the other, at the above-described element mass ratios. The fluorine compound and the phosphorus compound are uniformly distributed in the cross-sectional thickness direction of the separator, thereby reducing the electrical resistance of the separator.

[0013] The nonwoven fabric contained in the separator has a resistance of 30 seconds / 100 cm ３ More than 50 seconds / 100cm ３ The denser the nonwoven fabric, the easier it is to retain the fluorine compound and the phosphorus compound, and the more effectively it can prevent the fluorine compound and the phosphorus compound from leaking out to the positive electrode or the negative electrode. In addition, the denser the nonwoven fabric, the smaller the heat shrinkage rate of the nonwoven fabric itself. Therefore, the separator has an air permeability of 50 seconds / 100 cm. ３By including a dense nonwoven fabric having an air permeability of 30 sec / 100 cm or less, the thermal shrinkage rate in the in-plane direction is small, thereby increasing the safety of the battery. From the viewpoint of the transportability of charge carrier ions (e.g., Li ions) and thus the output performance of the battery, it is desirable that the separator is not too dense. Therefore, ３ By using a separator containing the above nonwoven fabric, the battery can exhibit high output. Nonwoven fabric with smaller fiber diameters tends to be denser, with fibers coming into contact with each other more frequently.

[0014] Next, details of the nonaqueous electrolyte battery according to the first embodiment will be described. The nonaqueous electrolyte battery may include an electrode assembly. The electrode assembly includes 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. Furthermore, the negative electrode may include a negative electrode current collector tab electrically connected to the electrode assembly.

[0015] Such a nonaqueous electrolyte battery may further include a housing member. The electrode group may be housed within the housing member. The housing member may house a nonaqueous electrolyte. The nonaqueous electrolyte may be impregnated into the electrode group housed within the housing member. The nonaqueous electrolyte battery may further include a positive electrode terminal and a negative electrode terminal electrically connected to the housing member. The positive electrode terminal may be electrically connected to a positive electrode current collector tab of the positive electrode. The negative electrode terminal may be electrically connected to a negative electrode current collector tab of the negative electrode.

[0016] 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.

[0017] The positive electrode, negative electrode, non-aqueous electrolyte, separator, exterior member, positive electrode terminal, and negative electrode terminal will be described in detail below.

[0018] Positive Electrode The positive electrode includes a positive electrode active material-containing layer. The positive electrode may further include a positive electrode current collector on which the positive electrode active material-containing layer is provided. When the positive electrode current collector has, for example, a sheet shape, the positive electrode active material-containing layer may be supported on at least one main surface of the positive electrode current collector. The positive electrode active material-containing layer includes a positive electrode active material. The positive electrode active material-containing layer may include a material other than the positive electrode active material, such as a conductive agent or a binder.

[0019] The positive electrode active material is not particularly limited. Examples of the positive electrode active material include lithium nickel cobalt manganese composite oxide (NCM: for example, Li x Ni 1-y-z Co y Mn z O2; 0<x≦1, 0<y<1, 0<z<1, y+z<1), lithium manganese composite oxide (LMO: for example, Li w Mn2O4 or Li w MnO2; 0.9≦w≦1.2), lithium nickel composite oxide (e.g., Li w NiO2; 0.9≦w≦1.2), lithium cobalt composite oxide (LCO: for example, Li w CoO2; 0.9≦w≦1.2), lithium nickel cobalt composite oxide (e.g., Li w Ni 1-x Co x O2 (0.9≦w≦1.2, 0<x≦1), lithium manganese cobalt composite oxide (e.g., Li w Mn x Co 1-x O2 (0.9≦w≦1.2, 0<x≦1), lithium iron phosphate (e.g., Li w FePO4 (0.9≦w≦1.2), and lithium complex phosphate compounds (e.g., manganese-containing lithium iron phosphate Li w Mn x Fe 1-xPO4 (LFP); 0.9≦w≦1.2, 0<x≦1). In a preferred embodiment, the active material as the positive electrode active material contains at least one selected from the group consisting of nickel cobalt manganese composite oxide (NCM), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), and lithium iron phosphate (LFP). The active material as the positive electrode active material can contain one or more of the active materials listed above. The active material as the positive electrode active material has a composition represented by the general formula Li x Ni 1-y-z Co y Mn z It is more desirable that the positive electrode active material contains a nickel-cobalt-manganese composite oxide represented by the formula: O2 (0<x≦1, 0<y<1, 0<z<1, y+z<1). The content of the nickel-cobalt-manganese composite oxide in the positive electrode active material is preferably 70% by mass or more and 100% by mass or less with respect to the total mass of the positive electrode active material.

[0020] The conductive agent can improve current collection performance and reduce contact resistance between the active material and the current collector. The conductive agent preferably contains a carbon material. Examples of carbon materials include acetylene black, ketjen black, furnace black, graphite, carbon nanotubes, and carbon nanofibers. The active material-containing layer can contain one or more of the above carbon materials.

[0021] The conductive agent has, for example, a particle or fiber shape. The average particle size of the conductive agent particles is preferably 20 nm or more and 100 nm or less. The proportion of the conductive agent in the positive electrode active material-containing layer is preferably, for example, 3 mass % or more and 20 mass % or less.

[0022] Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber. One or more types of binder may be used. The proportion of the binder in the positive electrode active material-containing layer is preferably 1% by mass or more and 1.8% by mass or less.

[0023] The density of the positive electrode active material-containing layer is 3.2 g / cm 3 3.8g / cm or more3 It is preferable that:

[0024] The positive electrode current collector may be, for example, a metal foil or an alloy foil. Examples of the metal foil include aluminum foil, stainless steel foil, and nickel foil. Examples of the alloy foil include aluminum alloy, copper alloy, and nickel alloy.

[0025] The positive electrode is produced, for example, by the following method. A positive electrode active material, a conductive agent, and a binder are kneaded together with a solvent (for example, N-methylpyrrolidone (NMP)) to prepare a slurry. The obtained slurry is applied to a positive electrode current collector, dried, and then pressed to obtain a positive electrode. The density of the positive electrode active material-containing layer can be adjusted by pressing with a load according to the composition of the positive electrode active material-containing layer. Furthermore, if necessary, a cutting step to a predetermined width may be performed before or after pressing.

[0026] The negative electrode includes, for example, a negative electrode current collector and a negative electrode active material-containing layer formed on the negative electrode current collector. The negative electrode active material-containing layer may contain a conductive agent and a binder in addition to the negative electrode active material.

[0027] The negative electrode active material, the conductive agent, the binder, and the negative electrode current collector will be described below.

[0028] The negative electrode active material has a potential of 0.4 V (vs. Li / Li) relative to the oxidation-reduction reaction potential of lithium. + ) or more. In a nonaqueous electrolyte battery equipped with such a negative electrode, lithium deposition due to charge and discharge can be suppressed. Therefore, such a nonaqueous electrolyte battery has superior rapid charge and discharge performance. Examples of the negative electrode active material include an anatase-type titanium-containing oxide, a rutile-type titanium-containing oxide, a monoclinic titanium-containing oxide, and Li 4+x TiO 12 (x varies in the range of -1≦x≦3 depending on the charge / discharge reaction), Li 2+xRamsdellite-type lithium titanate represented by Ti3O7 (x varies in the range of -1≦x≦3 depending on the charge / discharge reaction), monoclinic niobium titanium oxide represented by Nb2TiO7, Li 2-x TiO 14 At least one titanium-containing oxide is used, such as an orthorhombic titanium-containing oxide represented by the formula (x) (where x varies within the range of 0≦x≦6 depending on the charge / discharge reaction), or a metal composite oxide containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe. Examples of anatase-type titanium-containing oxides, rutile-type titanium-containing oxides, and monoclinic titanium-containing oxides include titanium dioxide represented by the formula TiO. Monoclinic titanium-containing oxides are also called bronze-type oxides and are sometimes expressed as TiO(B). Examples of metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe include TiO-P, TiO-V, TiO-P-SnO, and TiO-P-MO (where M is at least one element selected from the group consisting of Cu, Ni, and Fe). These metal composite oxides are converted into lithium-titanium composite oxides by intercalating lithium upon charging. Among the lithium-titanium composite oxides, spinel-type lithium titanate is preferred because it has excellent cycle performance.

[0029] As a negative electrode active material, the oxidation-reduction reaction potential of lithium is 0.5 V (vs. Li / Li + It is more preferable that the titanium-containing oxide contains a titanium-containing oxide that exhibits a reaction potential for lithium ion insertion and deintercalation at a potential of 1000 kJ / cm or more. Examples of such titanium-containing oxides include spinel-type lithium titanate, ramsdellite-type lithium titanate, monoclinic niobium titanium oxide, and orthorhombic titanium-containing oxide among the above-mentioned compounds.

[0030] The negative electrode active material may contain, for example, a carbonaceous material or a metal compound. Examples of the carbonaceous material include natural graphite, artificial graphite, coke, vapor-grown carbon fiber, mesophase pitch-based carbon fiber, spherical carbon, and resin-baked carbon. More preferred carbonaceous materials include vapor-grown carbon fiber, mesophase pitch-based carbon fiber, and spherical carbon. The carbonaceous material is preferably a material having a (002) plane spacing d ００２ is preferably 0.34 nm or less.

[0031] The metal compound may be a metal sulfide or a metal nitride, such as titanium sulfide, e.g., TiS, molybdenum sulfide, e.g., MoS, and FeS, FeS, or Li. x Iron sulfides such as FeS (0≦x≦2) can be used. Metal nitrides include lithium cobalt nitride (e.g., Li s Co t N, 0<s<4, 0<t<0.5) can be used. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black, and graphite.

[0032] Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and styrene-butadiene rubber.

[0033] When the negative electrode active material is a material capable of inserting and extracting lithium ions, the negative electrode current collector can be made of a material that is electrochemically stable at the lithium ion insertion and extraction potential of the negative electrode active material. The negative electrode current collector is preferably a metal foil made of at least one element selected from the group consisting of copper, nickel, stainless steel, and aluminum, or an alloy foil made of an aluminum alloy containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si. The shape of the negative electrode current collector can vary depending on the application of the battery.

[0034] The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a binder, and, if necessary, a conductive agent are suspended in a commonly used solvent, such as N-methylpyrrolidone, to prepare a slurry for producing the negative electrode. The obtained slurry is applied to a negative electrode current collector. The applied slurry is dried, and the dried coating is pressed to obtain a negative electrode including a negative electrode current collector and a negative electrode active material-containing layer formed on the negative electrode current collector.

[0035] The separator includes a nonwoven fabric. The nonwoven fabric is, for example, a nonwoven fabric containing cellulose. In addition to the cellulose fibers that make up the nonwoven fabric, the separator may further include one or more other constituent materials. Materials that can be combined with cellulose are not particularly limited, but examples thereof include polyolefin, polyester, polyvinyl alcohol, polyamide, polyimide, polytetrafluoroethylene, and vinylon.

[0036] The cellulose fiber diameter is, for example, 40 nm or more and 240 nm or less.The separator thickness can be 5 μm or more and 20 μm or less.

[0037] The electrode group may have, for example, a wound structure in which a stack of positive electrodes, separators, and negative electrodes is wound, or a stack structure in which multiple positive electrodes and multiple negative electrodes are alternately stacked with separators interposed therebetween, or the electrode group may have another structure.

[0038] Nonaqueous Electrolyte The nonaqueous electrolyte includes a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. An example of the nonaqueous electrolyte is a liquid nonaqueous electrolyte. Another example of the nonaqueous electrolyte is a gel nonaqueous electrolyte. The gel nonaqueous electrolyte is prepared by combining the liquid nonaqueous electrolyte with a polymer material.

[0039] Examples of electrolyte salts include LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), Li(CF3SO2)2N (lithium bistrifluoromethanesulfonylamide; commonly known as LiTFSI), LiCF3SO3 (lithium trifluoromethanesulfonate; commonly known as LiTFS), Li(C2F5SO2)2N (lithium bispentafluoroethanesulfonylamide; commonly known as LiBETI), LiClO4, and LiAsF6 (lithium hexafluoroarsenic Examples of the electrolyte salt include lithium salts such as lithium bisoxalatoborate (LiB(CO); commonly known as LiBOB), lithium difluoro(oxalato)borate (LiFBCO), lithium difluoro(trifluoro-2-oxido-2-trifluoro-methylpropionato(2-)-0,0)borate (LiBF(OCOOC(CF); commonly known as LiBF(HHIB)), and lithium difluorophosphate (LiPOF). These electrolyte salts may be used alone or in combination of two or more. In particular, LiPF, LiBF, lithium bisoxalatoborate (commonly known as LiBOB), lithium difluoro(oxalato)borate (LiFBCO), lithium difluoro(trifluoro-2-oxido-2-trifluoro-methylpropionato(2-)-0,0)borate (commonly known as LiBF(HHIB)), and lithium difluorophosphate (LiPOF) are preferred as the electrolyte salt.

[0040] The electrolyte salt concentration in the non-aqueous electrolyte is preferably in the range of 0.5 M to 3 M. This can improve performance when a high load current is applied.

[0041] The non-aqueous solvent is not particularly limited, but examples thereof include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), dipropyl carbonate (DPC), 1,2-dimethoxyethane (DME), γ-butyrolactone (GBL), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeHF), 1,3-dioxolane, sulfolane, and acetonitrile (AN). These solvents may be used alone or in combination of two or more. When combining two or more solvents, it is preferable to select each solvent having a dielectric constant of 20 or more.

[0042] The non-aqueous electrolyte may further contain other components. The other components are not particularly limited, but examples thereof include vinylene carbonate (VC), fluorovinylene carbonate, methylvinylene carbonate, fluoromethylvinylene carbonate, ethylvinylene carbonate, propylvinylene carbonate, butylvinylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate, dipropylvinylene carbonate, vinylene acetate (VA), vinylene butyrate, vinylene hexanate, vinylene crotonate, catechol carbonate, propane sultone, and butane sultone. One or more of these other components may be added.

[0043] The exterior member may be, for example, a laminate film or a metal container. The thickness of the laminate film and the metal container may each be 0.5 mm or less. Alternatively, the exterior member may be a resin container made of polyolefin resin, polyvinyl chloride resin, polystyrene resin, acrylic resin, phenolic resin, polyphenylene resin, fluorine resin, or the like.

[0044] The shape of the exterior member, i.e., the battery shape, can be flat (thin), rectangular, cylindrical, coin, button, etc. The battery can be used in both small applications such as those installed in portable electronic devices and large applications such as those installed in two-wheeled to four-wheeled automobiles.

[0045] Examples of laminate films include multilayer films containing resin layers and metal layers interposed between the resin layers. The metal layers are preferably aluminum foil or aluminum alloy foil for weight reduction. The resin layers can be made of polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The laminate film can be sealed by heat fusion to form it into the shape of an exterior component.

[0046] The metal container is made of aluminum or an aluminum alloy. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, silicon, etc. When the alloy contains a transition metal such as iron, copper, nickel, or chromium, the amount of the transition metal is preferably 100 ppm by mass or less.

[0047] Positive 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 transferring electrons between the positive electrode and an external circuit. The positive electrode terminal can be connected, for example, to the positive electrode current collector, particularly the positive electrode current collector tab. Alternatively, the positive electrode terminal can be connected, for example, to the positive electrode current collector tab via a positive electrode lead.

[0048] The positive electrode terminal has a potential of, for example, 3.0 V or more and 4.5 V or less with respect to the Li oxidation-reduction reaction potential (vs. Li / Li + The positive electrode terminal is preferably formed from a material that is electrically stable at a high potential and has electrical conductivity. The positive electrode terminal is preferably formed from aluminum or an aluminum alloy containing one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0049] The positive electrode terminal is preferably made of a material with high electrical conductivity. When connected to the positive electrode current collector, the positive electrode terminal is preferably made of the same material as the current collector. Using the same material can reduce the contact resistance between the positive electrode terminal and the positive electrode current collector. Similarly, the positive electrode lead is preferably made of the same material as the positive electrode terminal and the positive electrode current collector.

[0050] A portion of the negative electrode terminal is electrically connected to a portion of the negative electrode, thereby serving as a conductor for transferring electrons between the negative electrode and an external circuit. The negative electrode terminal can be connected, for example, to the negative electrode current collector, particularly the negative electrode current collector tab. Alternatively, the negative electrode terminal can be connected, for example, to the negative electrode current collector tab via a negative electrode lead.

[0051] The negative electrode terminal is between 0.5V and 3.0V relative to the Li oxidation-reduction reaction potential (vs. Li / Li + The negative electrode terminal is preferably formed from a material that is electrically stable at a high potential and has electrical conductivity. The negative electrode terminal is preferably formed from aluminum or an aluminum alloy containing one or more elements selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0052] The negative electrode terminal is preferably made of a material with high electrical conductivity. When connected to the negative electrode current collector, the negative electrode terminal is preferably made of the same material as the current collector. Using the same material can reduce the contact resistance between the negative electrode terminal and the negative electrode current collector. Similarly, the negative electrode lead is preferably made of the same material as the negative electrode terminal and the negative electrode current collector.

[0053] Next, an example of such a nonaqueous electrolyte battery will be described in more detail with reference to the drawings.

[0054] Fig. 1 is an exploded perspective view of an example of a nonaqueous electrolyte battery 100 according to an embodiment. The battery shown in Fig. 1 is a sealed prismatic nonaqueous electrolyte battery. The illustrated nonaqueous electrolyte battery 100 includes an outer can 1, a lid 2, a positive electrode external terminal 3, a negative electrode external terminal 4, and an electrode group 5. The outer can 1 and the lid 2 form an outer casing member. The outer can 1 has a bottomed rectangular cylindrical shape and is made of a metal such as aluminum, an aluminum alloy, iron, or stainless steel.

[0055] 2 is a partially exploded perspective view of an electrode group used in the nonaqueous electrolyte battery 100 shown in FIG. As shown in FIG. 2 , the flat electrode group 5 includes a positive electrode 6 and a negative electrode 7 wound in a flat shape with a separator 8 interposed therebetween. The positive electrode 6 includes a strip-shaped positive electrode current collector made of, for example, metal foil, a positive electrode current collector tab 6a formed at one end of the positive electrode current collector parallel to the long sides, and a positive electrode active material-containing layer 6b formed on the positive electrode current collector except for at least the portion of the positive electrode current collector tab 6a. Meanwhile, the negative electrode 7 includes a strip-shaped negative electrode current collector made of, for example, metal foil, a negative electrode current collector tab 7a formed at one end of the negative electrode current collector parallel to the long sides, and a negative electrode active material-containing layer 7b formed on the negative electrode current collector except for at least the portion of the negative electrode current collector tab 7a.

[0056] The positive electrode 6, separator 8, and negative electrode 7 are wound with the positive electrode 6 and negative electrode 7 offset from each other so that the positive electrode current collector tab 6a protrudes from the separator 8 in the direction of the winding axis of the electrode group, and the negative electrode current collector tab 7a protrudes from the separator 8 in the opposite direction. As a result of this winding, the electrode group 5 has the spirally wound positive electrode current collector tab 6a protruding from one end face, and the spirally wound negative electrode current collector tab 7a protruding from the other end face, as shown in Fig. 2 . The electrode group 5 is impregnated with a nonaqueous electrolyte (not shown).

[0057] As shown in Fig. 1, the positive electrode current collector tabs 6a and the negative electrode current collector tabs 7a are each divided into two bundles, with the boundary near the winding center of the electrode group. The conductive clamping member 9 has first and second clamping portions 9a and 9b each having a substantially U-shape, and a connecting portion 9c that electrically connects the first clamping portion 9a and the second clamping portion 9b. One bundle of the positive and negative electrode current collector tabs 6a and 7a is clamped by the first clamping portion 9a, and the other bundle is clamped by the second clamping portion 9b.

[0058] The positive electrode lead 10 has a substantially rectangular support plate 10a, a through hole 10b opened in the support plate 10a, and strip-shaped current collecting portions 10c and 10d that branch into two from the support plate 10a and extend downward. On the other hand, the negative electrode lead 11 has a substantially rectangular support plate 11a, a through hole 11b opened in the support plate 11a, and strip-shaped current collecting portions 11c and 11d that branch into two from the support plate 11a and extend downward.

[0059] The positive electrode lead 10 sandwiches the clamping member 9 between the current collecting portions 10c and 10d. The current collecting portion 10c is disposed in the first clamping portion 9a of the clamping member 9. The current collecting portion 10d is disposed in the second clamping portion 9b. The current collecting portions 10c and 10d, the first and second clamping portions 9a and 9b, and the positive electrode current collecting tab 6a are joined by, for example, ultrasonic welding. This electrically connects the positive electrode 6 of the electrode group 5 and the positive electrode lead 10 via the positive electrode current collecting tab 6a.

[0060] The negative electrode lead 11 sandwiches the clamping member 9 between the current collecting portions 11c and 11d. The current collecting portion 11c is disposed in the first clamping portion 9a of the clamping member 9. The current collecting portion 11d is disposed in the second clamping portion 9b. The current collecting portions 11c and 11d, the first and second clamping portions 9a and 9b, and the negative electrode current collecting tab 7a are joined by, for example, ultrasonic welding. This electrically connects the negative electrode 7 of the electrode group 5 and the negative electrode lead 11 via the negative electrode current collecting tab 7a.

[0061] The materials of the positive and negative electrode leads 10, 11 and the clamping member 9 are not particularly specified, but are preferably the same as the materials of the positive and negative electrode external terminals 3, 4, respectively. For example, aluminum or an aluminum alloy is used for the positive electrode external terminal 3. For example, aluminum, an aluminum alloy, copper, nickel, nickel-plated iron, or the like is used for the negative electrode external terminal 4. For example, when the material of the external terminals is aluminum or an aluminum alloy, it is preferable that the material of the leads is aluminum or an aluminum alloy. Furthermore, when the external terminals are copper, it is preferable that the material of the leads is copper, or the like.

[0062] The rectangular plate-shaped lid 2 is seam-welded to the opening of the outer can 1, for example, by laser. The lid 2 is made of a metal such as aluminum, an aluminum alloy, iron, or stainless steel. It is desirable that the lid 2 and the outer can 1 are made of the same type of metal. The positive electrode external terminal 3 is electrically connected to the support plate 10a of the positive electrode lead 10. The negative electrode external terminal 4 is electrically connected to the support plate 11a of the negative electrode lead 11. The insulating gasket 12 is disposed between the positive and negative electrode external terminals 3, 4 and the lid 2, and electrically insulates the positive and negative electrode external terminals 3, 4 from the lid 2. It is desirable that the insulating gasket 12 is a resin molded product.

[0063] <Manufacturing Method> The battery according to the embodiment can be manufactured, for example, as follows. A positive electrode, a negative electrode, and a nonwoven fabric are prepared. The positive electrode and the negative electrode can be manufactured, for example, by the methods described above. The nonwoven fabric can be a nonwoven fabric made of fibers such as cellulose, which is commonly used as a nonwoven fabric separator. The nonwoven fabric has an air permeability of 30 seconds / 100 cm. ３ More than 50 seconds / 100cm ３ The following nonwoven fabric is used. For example, a nonwoven fabric having constituent fibers with a fiber diameter of 40 nm or more and 240 nm or less can be used. A non-aqueous electrolyte is prepared separately, and an exterior member, a positive electrode terminal, and a negative electrode terminal are prepared. The non-aqueous electrolyte can be prepared by dissolving an electrolyte salt in the non-aqueous solvent described above. Optionally, other additives may be added to the non-aqueous electrolyte. The exterior member, the positive electrode terminal, and the negative electrode terminal can each be those described above.

[0064] A battery precursor is assembled using each component so that the nonwoven fabric is positioned between the positive electrode and the negative electrode within the exterior member, and the positive electrode, negative electrode, and nonwoven fabric are each impregnated with a nonaqueous electrolyte. An electrode assembly may be produced using a positive electrode, a negative electrode, and a nonwoven fabric. At least one nonwoven fabric is laminated so that the nonwoven fabric acts as a separator between the positive electrode and the negative electrode, and the resulting laminate is pressed or spirally wound as needed to produce an electrode assembly. The positive electrode terminal is electrically connected to the positive electrode, and the negative electrode terminal is electrically connected to the negative electrode.

[0065] The battery precursor obtained by enclosing other components within the exterior member is subjected to initial charge / discharge in a high-temperature environment of 45°C to 60°C. By using a nonwoven fabric having a density and mesh size that exhibits the above-mentioned air permeability as a separator and performing initial charge / discharge under these conditions, a fluorine compound derived from the nonaqueous electrolyte can be precipitated on the surface and interior of the nonwoven fabric in an amount such that the fluorine mass ratio is 10% to 20%, and a phosphorus compound derived from the nonaqueous electrolyte can be precipitated on the surface and interior of the nonwoven fabric in an amount such that the phosphorus mass ratio is 4% to 10%. In the dense nonwoven fabric described above, the frequency of fibers present within the nonwoven fabric is high, providing many locations where fluorine compounds and phosphorus compounds can precipitate. The fluorine compounds and phosphorus compounds form particulate precipitates attached to or entangled with the fibers, and do not form a film or layer that widely covers the nonwoven fabric surface (separator surface). In this manner, a nonaqueous electrolyte battery according to the embodiment can be obtained.

[0066] In contrast, when a nonwoven fabric with large mesh is used, the fluorine and phosphorus components in the nonaqueous electrolyte tend to leak out to the electrodes even after the initial charge / discharge cycle under the above conditions, resulting in precipitation of fluorine and phosphorus compounds on the electrodes, but little or no precipitation of fluorine and phosphorus compounds on the separator.

[0067] <Various Measurement Methods> Hereinafter, the methods for measuring the fluorine mass ratio, phosphorus mass ratio, and fiber diameter of the separator, the air permeability of the nonwoven fabric, and the composition of the electrode active material will be described. First, a method for removing the electrode from the battery will be described.

[0068] First, a battery to be measured is prepared. The battery to be measured has a discharge capacity of 80% or more of its rated capacity. In other words, batteries that have deteriorated excessively are not to be measured.

[0069] Next, the prepared battery is discharged until the open circuit voltage reaches 2.0 V to 2.2 V. Next, the discharged battery is transferred to a glove box filled with argon, the dew point of the internal atmosphere of which is −70° C. The battery is opened in the glove box. The electrode group is removed from the cut-open battery. If the removed electrode group includes a positive electrode lead and a negative electrode lead, the positive electrode lead and the negative electrode lead are cut off, taking care not to short-circuit the positive electrode and the negative electrode.

[0070] Next, the electrode assembly is disassembled into a positive electrode, a negative electrode, and a separator. In the case of a wound-type electrode assembly, each component is sampled from the innermost portion of the wound structure, where the positive electrode and negative electrode face each other through the separator. In the case of a stacked-type electrode assembly, each component is sampled from the central laminate portion in the thickness direction of the laminate. The electrodes and separators obtained in this manner are washed using diethyl carbonate as a solvent. In this washing, the disassembled components are completely immersed in the diethyl carbonate solvent and left in this state for 60 minutes. Since electrolyte salt remaining on the electrodes and separator affects the measurement results, thorough washing is performed in this manner to ensure that no electrolyte salt remains. Fluorine-containing compounds and phosphorus-containing compounds contained in the separator remain supported on the separator even after washing.

[0071] After washing, each component is subjected to vacuum drying. During vacuum drying, the pressure is reduced from atmospheric pressure to -97 kPa or higher in a 25°C environment, and this state is maintained for 10 minutes. The separator and electrodes removed in this manner are measured using the following method.

[0072] The fluorine mass ratio, phosphorus mass ratio, and fiber diameter of the separator surface were measured as follows. Platinum was sputtered onto both sides of the separator using a JEOL ion sputter. Then, using a Hitachi High-Technologies Miniscope TM3030 tabletop microscope, observation was performed using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) at a magnification of 10,000x to measure the abundance ratios of various elements and fiber diameters. Measurement points were the center of the separator surface and the four corners of a 2 cm square centered on the center, for a total of five points. The abundance ratios of various elements measured in the observation field were quantitatively analyzed on a mass (weight) basis to determine the mass ratios of each element.

[0073] To measure the separator cross section, an ion milling machine IM4000 manufactured by Hitachi High-Technologies was used. The separator was cooled with liquid nitrogen during milling to prevent thermal shrinkage. Platinum was then sputtered in the same manner as the separator surface, and SEM-EDX observation was performed, measuring the central one-third of the separator in the thickness direction. A total of five measurement points were measured, each shifted by 1 cm in the separator flow direction.

[0074] Although it is possible to distinguish between fibers and fluorine compounds and phosphorus compounds by visual inspection of SEM images, it is desirable to use EDX for quantitative analysis of the mass ratios of fluorine and phosphorus. Furthermore, carbon (C) and oxygen (O) are detected by EDX in the portions of the fibers that make up the nonwoven fabric, such as cellulose fibers, that are not coated with fluorine compounds or phosphorus compounds.

[0075] The air permeability of the nonwoven fabric contained in the separator is determined by the Gurley method defined in Japanese Industrial Standard JIS P 8117:2009. ３ The time it takes for air to pass through the nonwoven fabric is measured. The denser the nonwoven fabric, the longer it takes for air to pass through.

[0076] Composition of the Active Material The composition of the active material can be obtained by measuring the surface of the electrode taken out of the battery by the above-mentioned method using X-ray fluorescence (XRF).

[0077] The nonaqueous electrolyte battery according to the first embodiment includes a separator containing, on both sides and inside thereof, a fluorine compound with a fluorine mass ratio of 10% to 20% and a phosphorus compound with a phosphorus mass ratio of 4% to 10%. Therefore, the battery can achieve both high capacity and high safety.

[0078] Second Embodiment According to a second embodiment, a battery pack including a battery is provided. The battery is the nonaqueous electrolyte battery according to the first embodiment. The number of cells included in the battery pack can be one or more.

[0079] A plurality of batteries can be electrically connected in series, in parallel, or in a combination of series and parallel to form a battery assembly. A battery pack may include a plurality of battery assembly.

[0080] The battery pack may further include a protection circuit. The protection circuit has a function of controlling the charging and discharging of the battery. Furthermore, a circuit included in a device that uses the battery pack as a power source (e.g., electronic equipment, automobile, etc.) may be used as the protection circuit for the battery pack.

[0081] The battery pack may further include external current-carrying terminals. The external current-carrying terminals are used to output current from the battery to the outside and input current to the battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external current-carrying terminals. When the battery pack is charged, charging current (including regenerative energy from the vehicle's power) is supplied to the battery pack through the external current-carrying terminals.

[0082] Next, an example of a battery pack according to a second embodiment will be described with reference to the drawings. Fig. 3 is a block diagram showing an example of an electric circuit of the battery pack according to the embodiment.

[0083] The battery pack shown in Fig. 3 includes a plurality of flat-type cells 100 having the structure shown in Fig. 1 and Fig. 2. These cells 100 are electrically connected in series with one another as shown in Fig. 3.

[0084] In addition to the cells 100, the battery pack is equipped with a thermistor 25, a protection circuit 26, and external terminals 27 for applying current.

[0085] At one end of the series connection, a positive electrode lead 28 is connected to the positive electrode external terminal of the cell 100. The positive electrode lead 28 is electrically connected to the protection circuit 26 via a positive electrode connector 29 and wiring 32. At the other end of the series connection, a negative electrode lead 30 is connected to the negative electrode external terminal of the cell 100. The negative electrode lead 30 is electrically connected to the protection circuit 26 via a negative electrode connector 31 and wiring 33.

[0086] The thermistor 25 detects the temperature of each cell 100 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 external terminal 27 for current supply under predetermined conditions. An example of the predetermined condition is when a signal is received from the thermistor 25 indicating that the temperature of the cell 100 is equal to or higher than a predetermined temperature. Another example of the predetermined condition is when overcharge, overdischarge, overcurrent, or the like of the cell 100 is detected. This overcharge detection is performed for each cell 100 or for all cells 100. When detecting each cell 100, 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 100. In the battery pack shown in FIG. 3 , each cell 100 is connected to wiring 35 for voltage detection, and a detection signal is transmitted to the protection circuit 26 through these wirings 35.

[0087] Although the illustrated battery pack has a configuration in which a plurality of cells 100 are connected in series, the battery pack may also have a plurality of cells 100 connected in parallel to increase battery capacity. Alternatively, the battery pack may have a plurality of cells 100 connected in a combination of series and parallel connections. Assembled battery packs may also be connected in series or parallel.

[0088] Furthermore, although the illustrated battery pack includes a plurality of unit cells 100 , the battery pack according to the second embodiment may include a single unit cell 100 .

[0089] The battery pack configuration may be changed as appropriate depending on the intended use. Preferred uses of the battery pack are those that require good cycle performance when drawing a large current. Specific examples 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 preferred.

[0090] In an automobile equipped with a battery pack according to this embodiment, the battery pack recovers, for example, regenerative energy for powering the automobile.

[0091] The battery pack according to the second embodiment described above in detail includes the nonaqueous electrolyte battery according to the first embodiment, and therefore, this battery pack can achieve both high output performance and high safety.

[0092] <Preparation of non-aqueous electrolyte battery> (Example 1) (Preparation of positive electrode) A lithium nickel cobalt manganese composite oxide (LiNi) was used as the positive electrode active material. 0.8 Co 0.1 Mn 0.1 O2 (NCM) was prepared. Graphite and acetylene black were prepared as conductive agents. Polyvinylidene fluoride (PVdF) was prepared as a binder. The NCM, graphite, acetylene black, and PVdF were dissolved and mixed in N-methylpyrrolidone (NMP) in a mass ratio of 93:2.5:2.5:2 to prepare a paste.

[0093] The specific method for preparing the paste is described below. The active material and conductive agent were mixed using a Henschel mixer to form a composite (compound) of the active material and conductive agent. The resulting composite and binder were dispersed in NMP and kneaded using a planetary mixer with a capacity of 20 L. To avoid a sudden increase in viscosity, each material was added to the NMP little by little. The kneading was performed under high-temperature conditions with a solids concentration (non-volatile content; NV) of 78.5%.

[0094] The paste-like dispersion liquid was used as a positive electrode coating liquid and uniformly applied to both the front and back surfaces of a strip-shaped current collector made of aluminum foil. The positive electrode coating liquid coating film was dried to form a positive electrode active material-containing layer. After drying, the strip-shaped product was press-molded under the following conditions: A press roll made of a hard chrome-plated steel roll with a press roll diameter of 350 mm was used, and the press load was set to approximately 8 kN / cm.

[0095] (Preparation of negative electrode) Li4Ti5O was used as the negative electrode active material. 12 A spinel-type lithium titanium oxide represented by the formula (I), graphite as a conductive agent, and polyvinylidene fluoride as a binder were prepared. These negative electrode active materials, conductive agent, and binder were dissolved and mixed in NMP in a mass ratio of 94:4:2 to prepare a paste. This paste was used as a negative electrode coating liquid and uniformly applied to both the front and back surfaces of a negative electrode current collector made of strip-shaped aluminum foil. The negative electrode coating liquid was dried to form a negative electrode active material-containing layer. The dried strip was press-molded and then cut to a predetermined size. The electrode thickness was adjusted to 130 μm.

[0096] (Preparation of electrode group) Two strip-shaped nonwoven separators made of cellulose were prepared. The average fiber diameter of the cellulose contained in each separator was 100 nm, and the air permeability of each separator was 40 sec / 100 cm ３ Next, one separator, the positive electrode, the other separator, and the negative electrode were stacked in this order to form a laminate. The resulting laminate was wound so that the separator was positioned at the outermost periphery to obtain a wound body. The resulting wound body (coil) was then pressed while being heated. In this way, a wound electrode group was produced.

[0097] (Preparation of Nonaqueous Electrolyte) A mixed solvent was prepared by mixing 33% by volume of ethylene carbonate (EC) and 67% by volume of diethyl carbonate (DEC) as a nonaqueous solvent. 1 M of LiPF was dissolved in the mixed solvent as an electrolyte salt to prepare a liquid nonaqueous electrolyte (nonaqueous electrolyte solution).

[0098] (Battery Assembly) Electrode terminals were electrically connected to the positive and negative electrodes of the wound electrode assembly obtained as described above. The electrode assembly was placed in an aluminum rectangular container. The nonaqueous electrolyte described above was poured into the container, and the container was sealed to obtain a precursor for a nonaqueous electrolyte battery. The obtained battery precursor was charged and discharged at 60°C to precipitate fluorine compounds and phosphorus compounds on the inside and outside of the separator. In this way, a nonaqueous electrolyte battery including a separator carrying fluorine compounds and phosphorus compounds on both surfaces and in the interior was fabricated. The nonaqueous electrolyte battery was designed to have a nominal capacity of 26 Ah.

[0099] Examples 2 to 4 The separator was changed to a cellulose nonwoven fabric separator having the average fiber diameter and air permeability shown in Table 1. Otherwise, nonaqueous electrolyte batteries were fabricated in the same manner as in Example 1.

[0100] Comparative Examples 1 to 4 Non-aqueous electrolyte batteries were fabricated in the same manner as in Example 1, except that the separator was changed to a cellulose nonwoven fabric separator having the average fiber diameter and air permeability shown in Table 1 below.

[0101] (Comparative Example 5) Before fabricating the electrode assembly, a material paste containing a fluorine compound and a phosphorus compound was applied to one main surface of each separator, and the paste was dried. After sealing the electrode assembly and non-aqueous electrolyte in the square container, charge / discharge at 60°C was omitted. A non-aqueous electrolyte battery was fabricated in the same manner as in Example 1, except for these changes.

[0102] (Comparative Example 6) Before fabricating the electrode assembly, a material paste containing a fluorine compound and a phosphorus compound was applied to both main surfaces of each separator, and the paste was dried. After sealing the electrode assembly and non-aqueous electrolyte in the square container, charge / discharge at 60°C was omitted. A non-aqueous electrolyte battery was fabricated in the same manner as in Example 1, except for these changes.

[0103] <Measurement> For the separator included in each battery example, the battery was disassembled and removed using the method described above, and SEM-EDX observation was performed on both the front and back surfaces and the cross section to measure the fluorine mass ratio and phosphorus mass ratio. However, for Comparative Example 5, only the surfaces coated with the fluorine compound and the phosphorus compound were observed. In addition, the carbon mass ratio and oxygen mass ratio were also measured for the separator surfaces observed for each example. The measurement results are shown in Table 1 below. The separator surface measurement results show the average of the measurements for the front and back sides, except for Comparative Example 5. For cross-sectional observation, the measurements are shown for the central 1 / 3 region in the thickness direction.

[0104] <Performance Evaluation> (In-Plane Heat Shrinkage of Separator) The in-plane heat shrinkage of the separator included in each battery example was measured as follows. The separator, which had been removed from the battery and washed using the method described above, was fixed by attaching tape to both ends of the main surface in the longitudinal direction of the strip shape. In the fixed state, the width in the lateral direction of the strip shape was measured. Thereafter, while still fixed, the separator was heated at 100°C for 12 hours. After heating, the width in the lateral direction of the strip shape was measured again. The difference in width before and after heating relative to the width before heating was calculated to determine the width direction heat shrinkage (width direction heat shrinkage = [(width before heating - width after heating) / width before heating] × 100%). The measurement results are shown in Table 1 below.

[0105] (Battery Output Performance) The discharge resistance of the batteries prepared in each example was measured by the following method to evaluate the output performance. First, the batteries were charged at a current of 1 C in an environment of 25° C. until the state of charge (SOC) reached 50%. The battery voltage at this time was measured and designated as voltage A. Next, the batteries charged to an SOC of 50% were discharged at a current of 10 C for 10 seconds. The battery voltage after discharge was measured and designated as voltage B. Next, the discharge resistance was calculated from the difference between voltage A after charge and voltage B after discharge and the current value. The measurement results are shown in Table 1 below.

[0106] (Safety) The safety of the batteries prepared in each example was evaluated using a method conforming to the nail penetration test in SAE J2464 specified by the Society of Automotive Engineers (SAE). Specifically, the evaluation was performed as follows. The batteries were charged at a current of 1 C in an environment of 25°C until the state of charge (SOC) reached 100%. Next, a 3.0 mm diameter nail was dropped onto the long side of the battery's outer container at a speed of 80 mm / sec, causing the nail to penetrate the battery. Batteries that did not explode or ignite when penetrated by the nail were deemed safe and rated "good." Batteries that exploded or ignited were deemed unsafe and rated "poor." The evaluation results are shown in Table 1 below.

[0107] Table 1 shows the average fiber diameter of the cellulose contained in the cellulose nonwoven fabric used for the separator in each example, the air permeability of the nonwoven fabric, the element abundance ratio measured by SEM-EDX observation of the surface and cross section of the separator, the width-direction heat shrinkage rate of the separator, the discharge resistance measured as an evaluation of output performance, and the evaluation results of safety by a nail penetration test.

[0108]

[0109] As shown in Table 1, the batteries fabricated in Examples 1 to 4 had low discharge resistance and did not explode or catch fire in the nail penetration test. In other words, the batteries in Examples 1 to 4 exhibited high output performance and high safety. In contrast, although Comparative Examples 1 and 4 had low discharge resistance, the results of the nail penetration test were poor and safety could not be achieved. Although Comparative Examples 2, 3, and 6 had good results in the nail penetration test, the discharge resistance was high and the output performance was not excellent. In Comparative Example 5, neither the output performance nor the safety performance was excellent.

[0110] In Comparative Example 1, the cellulose fiber diameter in the separator was large and the air permeability was low. The nonwoven fabric constituting the separator had a coarse weave, so the thermal shrinkage rate in the in-plane direction of the separator was large and safety was low.

[0111] In Comparative Example 2, the cellulose fiber diameter in the separator was small and the air permeability was high. The nonwoven fabric constituting the separator was dense, which resulted in low output performance of the battery.

[0112] In Comparative Example 3, the fluorine mass ratio and phosphorus mass ratio in the separator were high. The fluorine compound and phosphorus compound blocked the mesh of the nonwoven fabric that constituted the separator, resulting in poor output performance.

[0113] The fluorine mass ratio and phosphorus mass ratio in the separator were small in Comparative Example 4. Since the amounts of the fluorine compound and the phosphorus compound supported were small, the thermal shrinkage rate in the in-plane direction of the separator was large, and safety was low.

[0114] In Comparative Example 5, the fluorine compound and phosphorus compound were simply applied to one side of the separator, resulting in a small amount of fluorine and phosphorus inside the separator. Comparative Example 5 demonstrates that simply applying a compound containing fluorine or phosphorus to one side of the separator is insufficient to suppress the in-plane thermal shrinkage of the separator. As a result, Comparative Example 5 had low safety. Furthermore, Comparative Example 5 did not have excellent output performance due to the uneven distribution of fluorine and phosphorus in the thickness direction of the separator cross section.

[0115] In Comparative Example 6, the fluorine compound and phosphorus compound were simply applied to the separator surface, resulting in a small amount of fluorine and phosphorus inside the separator. In Comparative Example 6, safety was achieved by suppressing the thermal shrinkage of the separator in the in-plane direction, but the distribution of fluorine and phosphorus in the cross-sectional thickness direction within the separator was not uniform, resulting in high discharge resistance and poor output performance.

[0116] According to at least one of the above-described embodiments and examples, a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a positive electrode, a negative electrode, a separator interposed therebetween, and a nonaqueous electrolyte. The separator has an air permeability of 30 seconds / 100 cm ３ More than 50 seconds / 100cm ３ The separator includes a nonwoven fabric having the following characteristics: the fluorine mass ratio is 10% or more and 20% or less, and the phosphorus mass ratio is 4% or more and 10% or less on both main surfaces of the separator and in a region of the central one-third portion in the thickness direction of the separator. The nonaqueous electrolyte battery described above can achieve both high output and high safety.

[0117] 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 inventions and their equivalents as defined in the claims.

[0118]

[0013] Several embodiments of the present invention are described below. [1] A battery comprising: a positive electrode; a negative electrode; a separator between the positive electrode and the negative electrode, the separator including a nonwoven fabric; and a nonaqueous electrolyte, wherein the fluorine mass ratio is 10% to 20% and the phosphorus mass ratio is 4% to 10% on each of the front and back main surfaces of the separator and in a central one-third region in the thickness direction of the separator, and the nonwoven fabric has an air permeability of 30 seconds / 100 cm ３ More than 50 seconds / 100cm ３ A nonaqueous electrolyte battery according to the following: [2] The non-aqueous electrolyte battery according to [1], wherein the nonwoven fabric contains cellulose. [3] The non-aqueous electrolyte battery according to [1] or [2], wherein the positive electrode contains a lithium-nickel-cobalt-manganese composite oxide. [4] The non-aqueous electrolyte battery according to any one of [1] to [3], wherein the negative electrode contains a titanium-containing oxide. [5] A battery pack including the non-aqueous electrolyte battery according to any one of [1] to [4].

[0119] REFERENCE SIGNS LIST 1... outer can, 2... lid, 3... positive electrode external terminal, 4... negative electrode external terminal, 5... electrode group, 6... positive electrode, 6a... positive electrode current collecting tab, 6b... positive electrode active material containing layer, 7... negative electrode, 7a... negative electrode current collecting tab, 7b... negative electrode active material containing layer, 8... separator, 9... clamping member, 9a... first clamping portion, 9b... second clamping portion, 9c... connecting portion, 10... positive electrode lead, 10a... support plate, 10b... through hole, 10c... current collecting portion, 10d... current collecting portion 11...negative electrode lead, 11a...support plate, 11b...through hole, 11c...current collecting portion, 11d...current collecting portion, 12...insulating gasket, 25...thermistor, 26...protective circuit, 27...external terminal for current supply, 28...positive electrode side lead, 29...positive electrode side connector, 30...negative electrode side lead, 31...negative electrode side connector, 32...wiring, 33...wiring, 34a...positive side wiring, 34b...negative side wiring, 35...wiring, 100...single cell

Claims

1. A battery comprising: a positive electrode; a negative electrode; a separator between the positive electrode and the negative electrode, the separator including a nonwoven fabric; and a nonaqueous electrolyte; wherein the fluorine mass ratio is 10% or more and 20% or less, and the phosphorus mass ratio is 4% or more and 10% or less on each of the front and back main surfaces of the separator and in a central 1 / 3 region in the thickness direction of the separator; and the nonwoven fabric has an air permeability of 30 seconds / 100 cm. ３ More than 50 seconds / 100cm ３ A non-aqueous electrolyte battery as follows:

2. The non-aqueous electrolyte battery according to claim 1, wherein the nonwoven fabric comprises cellulose.

3. The nonaqueous electrolyte battery according to claim 1 or 2, wherein the positive electrode contains a lithium nickel cobalt manganese composite oxide.

4. The nonaqueous electrolyte battery according to claim 1 or 2, wherein the negative electrode contains a titanium-containing oxide.

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

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