Non-aqueous electrolyte storage element, method for manufacturing same, and non-aqueous electrolyte

Abstract

To provide a non-aqueous electrolyte power storage element that suppresses the occurrence of micro-short circuits during repeated charging and discharging when a negative electrode contains metallic lithium, a manufacturing method for the same, and a non-aqueous electrolyte for a lithium battery that can suppress the occurrence of micro-short circuits.SOLUTION: The non-aqueous electrolyte power storage element includes a negative electrode containing metallic lithium as well as a non-aqueous electrolyte containing polyvalent metal cations and imide anions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte storage element, a method for manufacturing the same, and a non-aqueous electrolyte.

Background Art

[0002] Non-aqueous electrolyte secondary batteries typified by lithium-ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, and automobiles because of their high energy density. Generally, the non-aqueous electrolyte secondary battery has a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring ions between both electrodes. In addition, as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries, capacitors such as lithium-ion capacitors and electric double layer capacitors are also widely spread. As a negative electrode active material having a high energy density used in non-aqueous electrolyte storage elements, metallic lithium is known (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In non-aqueous electrolyte storage elements in which metallic lithium is used as a negative electrode active material, such as lithium batteries, metallic lithium may precipitate dendritically on the surface of the negative electrode during charging (hereinafter, metallic lithium in a dendritic form is referred to as a "dendrite"). When this dendrite grows and penetrates the separator and comes into contact with the positive electrode, a micro short circuit is caused. For this reason, non-aqueous electrolyte storage elements containing metallic lithium as a negative electrode active material have the disadvantage that a micro short circuit is likely to occur due to repeated charge and discharge.

[0005] The present invention has been made based on the above circumstances, and an object thereof is to provide a non-aqueous electrolyte storage element in which the occurrence of a micro short circuit accompanying repeated charge and discharge is suppressed when the negative electrode contains metallic lithium, a method for manufacturing such a non-aqueous electrolyte storage element, and a non-aqueous electrolyte for a lithium battery capable of suppressing the occurrence of a micro short circuit.

Means for Solving the Problems

[0006] One aspect of the present invention is a non-aqueous electrolyte storage element including a negative electrode containing metallic lithium and a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion.

[0007] Another aspect of the present invention is a method for manufacturing a non-aqueous electrolyte storage element including preparing a negative electrode containing metallic lithium and preparing a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion.

[0008] Another aspect of the present invention is a non-aqueous electrolyte for a lithium battery containing a polyvalent metal cation and an imide anion.

Effects of the Invention

[0009] According to one aspect of the present invention, it is possible to provide a non-aqueous electrolyte storage element in which the occurrence of a micro short circuit accompanying repeated charge and discharge is suppressed when the negative electrode contains metallic lithium, a method for manufacturing such a non-aqueous electrolyte storage element, and a non-aqueous electrolyte for a lithium battery capable of suppressing the occurrence of a micro short circuit.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0011] First, an overview of the non-aqueous electrolyte energy storage device, the method for manufacturing the non-aqueous electrolyte energy storage device, and the non-aqueous electrolyte disclosed by this specification will be described.

[0012] A non-aqueous electrolyte energy storage device according to one aspect of the present invention is a non-aqueous electrolyte energy storage device including a negative electrode containing metallic lithium and a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion.

[0013] In this non-aqueous electrolyte energy storage device, although the negative electrode contains metallic lithium, the occurrence of micro short circuits associated with repeated charge and discharge is suppressed. That is, in this non-aqueous electrolyte energy storage device, the occurrence of micro short circuits caused by repeated charge and discharge is delayed. The reason for this is not clear, but the following reasons are speculated. First, since the polyvalent metal cation is polyvalent, cations and anions in the non-aqueous electrolyte are not completely dissociated, and it is speculated that the polyvalent metal cation and anions such as imide anions form ion pairs or partially dissociated multiple ions, and these ion pairs or multiple ions are in a solvated state. Therefore, when the polyvalent metal cation is reduced on the negative electrode surface to form a film, the decomposition of the imide anion also occurs, and as a result, the film formed contains components derived from the imide anion together with the polyvalent metal, and it is considered that the film becomes low resistance and of good quality. Second, when dendrites grow on the negative electrode surface, the growth of dendrites in the tip direction is suppressed by the reduction of polyvalent metal cations at the dendritic tips of the dendrites. As a result, the shape of the dendrites changes from dendritic to massive, and it is considered that the occurrence of micro short circuits associated with repeated charge and discharge is suppressed. From the above, it is speculated that in the non-aqueous electrolyte energy storage device according to one embodiment of the present invention including a negative electrode containing metallic lithium and a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion, the occurrence of micro short circuits associated with repeated charge and discharge is suppressed.

[0014] The above-mentioned polyvalent metal cation is preferably a cation of a Group 2 element, a Group 11 element, or a Group 12 element. When the cations of these elements are contained in the non-aqueous electrolyte, the occurrence of micro short circuits accompanying repeated charge and discharge is further suppressed.

[0015] The above-mentioned polyvalent metal cation is preferably a cation of magnesium or copper. When the cations of these elements are contained in the non-aqueous electrolyte, the occurrence of micro short circuits accompanying repeated charge and discharge is further suppressed.

[0016] The above-mentioned polyvalent metal cation is also preferably a cation of a representative element. Even when the polyvalent metal cation contained in the non-aqueous electrolyte is a cation of a representative element, the occurrence of micro short circuits accompanying repeated charge and discharge can be sufficiently suppressed.

[0017] The above-mentioned non-aqueous electrolyte preferably contains a fluorinated solvent. When the non-aqueous electrolyte contains a fluorinated solvent, the occurrence of micro short circuits accompanying repeated charge and discharge is further suppressed because the formed film becomes of better quality.

[0018] A method for manufacturing a non-aqueous electrolyte storage element according to one aspect of the present invention includes preparing a negative electrode containing metallic lithium and preparing a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion.

[0019] According to the manufacturing method, even though the negative electrode contains metallic lithium, a non-aqueous electrolyte storage element in which the occurrence of micro short circuits accompanying repeated charge and discharge is suppressed can be manufactured.

[0020] A non-aqueous electrolyte according to one aspect of the present invention is a non-aqueous electrolyte for a lithium battery containing a polyvalent metal cation and an imide anion.

[0021] According to the non-aqueous electrolyte, the occurrence of micro short circuits accompanying repeated charge and discharge in a lithium battery can be suppressed.

[0022] Hereinafter, the non-aqueous electrolyte storage element, the manufacturing method of the non-aqueous electrolyte storage element, and the non-aqueous electrolyte according to an embodiment of the present invention will be described in order.

[0023] <Non-aqueous electrolyte storage element> The non-aqueous electrolyte storage element according to an embodiment of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte. Hereinafter, as an example of the non-aqueous electrolyte storage element, a non-aqueous electrolyte secondary battery (hereinafter, also simply referred to as "secondary battery") will be described. The positive electrode and the negative electrode usually form an electrode body that is alternately stacked or wound via a separator. This electrode body is housed in a container, and the container is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. As the container, a known metal container, resin container, etc. that are usually used as the container of the secondary battery can be used.

[0024] (Positive electrode) The positive electrode has a positive electrode substrate and a positive electrode active material layer disposed directly or via an intermediate layer on the positive electrode substrate.

[0025] The positive electrode substrate has conductivity. Having "conductivity" means that the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 7 Ω·cm or less, and "non-conductive" means that the volume resistivity is more than 10 7 Ω·cm. As the material of the positive electrode substrate, metals such as aluminum, titanium, tantalum, and stainless steel, or their alloys are used. Among these, aluminum and aluminum alloys are preferable in terms of the balance of potential resistance, high conductivity, and cost. In addition, examples of the form of the positive electrode substrate include a foil and a vapor deposition film, and a foil is preferable in terms of cost. That is, an aluminum foil is preferable as the positive electrode substrate. Note that examples of aluminum or aluminum alloy include A1085P and A3003P defined in JIS-H-4000 (2014).

[0026] The average thickness of the positive electrode substrate is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, still more preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode substrate within the above range, it is possible to increase the strength of the positive electrode substrate and at the same time increase the energy density per unit volume of the secondary battery. The "average thickness" refers to the value obtained by dividing the punching mass when punching out a substrate with a predetermined area by the true density and the punching area of the substrate. Hereinafter, the "average thickness" of the negative electrode substrate and the negative electrode active material layer described later is the same.

[0027] The intermediate layer is a coating layer on the surface of the positive electrode substrate, and by containing conductive particles such as carbon particles, the contact resistance between the positive electrode substrate and the positive electrode active material layer can be reduced. The configuration of the intermediate layer is not particularly limited, and for example, it can be formed by a composition containing a resin binder and conductive particles.

[0028] The positive electrode active material layer is a layer formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode mixture forming the positive electrode active material layer may contain optional components such as a conductive agent, a binder, a thickener, and a filler as required.

[0029] The positive electrode active material can be appropriately selected from known positive electrode active materials. As the positive electrode active material for a lithium secondary battery, a material that can usually occlude and release lithium ions is generally used. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2-type crystal structure, lithium transition metal composite oxides having a spinel-type crystal structure, polyanion compounds, chalcogen compounds, sulfur, and the like. Examples of the lithium transition metal composite oxide having an α-NaFeO2-type crystal structure include Li[Li x Ni 1-x O2 (0 ≦ x < 0.5), Li[Li x Ni γ Co 1-x-γ O2 (0 ≦ x < 0.5, 0 < γ < 1), Li[Li x Co 1-x O2 (0 ≦ x < 0.5), Li[Li x Ni γ Mn 1-x-γO2(0 ≦ x < 0.5, 0 < γ < 1), Li[Li x Ni γ Mn β Co 1-x-γ-β O2(0 ≦ x < 0.5, 0 < γ, 0 < β, 0.5 < γ + β < 1), Li[Li x Ni γ Co β Al 1-x-γ-β O2(0 ≦ x < 0.5, 0 < γ, 0 < β, 0.5 < γ + β < 1), etc. are mentioned. As the lithium transition metal composite oxide having a spinel crystal structure, Li x Mn2O4, Li x Ni γ Mn 2-γ O4, etc. are mentioned. As the polyanion compound, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F, etc. are mentioned. As the chalcogen compound, titanium disulfide, molybdenum disulfide, molybdenum dioxide, etc. are mentioned. Atoms or polyanions in these materials may be partially substituted with atoms or anion species composed of other elements. These materials may have their surfaces coated with other materials. In the positive electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used.

[0030] As the positive electrode active material, a lithium transition metal composite oxide is preferable, and a lithium transition metal composite oxide having an α-NaFeO2 type crystal structure is more preferable. The lithium transition metal composite oxide preferably contains nickel or manganese as the transition metal, and more preferably contains both nickel and manganese. The lithium transition metal composite oxide may further contain other transition metals such as cobalt. In the lithium transition metal composite oxide having an α-NaFeO2 type crystal structure, the molar ratio of lithium (Li) to the transition metal (Me) (Li / Me) is preferably greater than 1, more preferably 1.1 or more, still more preferably 1.2 or more, and even more preferably 1.3 or more. By using such a lithium transition metal composite oxide, the capacitance can be increased. In the case of a non-aqueous electrolyte storage element using such a positive electrode active material, it tends to be used at a high current density, and usually, dendrites are likely to grow. Therefore, in the case of a non-aqueous electrolyte storage element including a positive electrode having the above lithium transition metal composite oxide, the effect of suppressing the occurrence of micro short circuits can be more significantly enjoyed. The upper limit of the molar ratio of lithium to the transition metal (Li / Me) is preferably 1.6, and more preferably 1.5.

[0031] As the lithium transition metal composite oxide having an α-NaFeO2 type crystal structure, a compound represented by the following formula (1) is preferable. Li 1+α Me 1-α O2···(1) In formula (1), Me is a transition metal containing Ni or Mn. 0 < α < 1.

[0032] Me in formula (1) preferably contains Ni and Mn. Me is preferably composed of substantially two elements of Ni and Mn, or three elements of Ni, Mn, and Co. Me may contain other transition metals.

[0033] In formula (1), the lower limit of the molar ratio of Ni to Me (Ni / Me) is preferably 0.1, more preferably 0.2. On the other hand, the upper limit of this molar ratio (Ni / Me) is preferably 0.5, more preferably 0.45. By setting the molar ratio (Ni / Me) within the above range, the energy density is improved.

[0034] In formula (1), the lower limit of the molar ratio of Mn to Me (Mn / Me) is preferably 0.5, more preferably 0.55, still more preferably 0.6. On the other hand, the upper limit of this molar ratio (Mn / Me) is preferably 0.75, more preferably 0.7. By setting the molar ratio (Mn / Me) within the above range, the energy density is improved.

[0035] In formula (1), the upper limit of the molar ratio of Co to Me (Co / Me) is preferably 0.3, more preferably 0.2, still more preferably 0.1. The lower limit of this molar ratio (Co / Me) may be 0.

[0036] In formula (1), the molar ratio of Li to Me, that is, (1 + α) / (1 - α), is preferably greater than 1.0 (α > 0), more preferably 1.1 or more, still more preferably 1.2 or more, and even more preferably 1.3 or more. On the other hand, the upper limit of this molar ratio (Li / Me) is preferably 1.6, more preferably 1.5. By setting the molar ratio (Li / Me) within the above range, the capacitance increases.

[0037] The lithium transition metal composite oxide in which the molar ratio of lithium (Li) to the above transition metal (Me) (Li / Me) is greater than 1 preferably has no diffraction peak in the range of 20° or more and 22° or less in the X-ray diffraction pattern using CuKα rays. The lithium transition metal composite oxide in which the molar ratio of lithium (Li) to the transition metal (Me) (Li / Me) is greater than 1 generally has a positive electrode potential of, for example, 4.5 V vs. Li / Li +By undergoing the initial charge and discharge up to the above, the capacitance increases. Further, due to the change in the crystal structure during such initial charge and discharge, the diffraction peak that existed in the range of 20° or more and 22° or less before the initial charge and discharge disappears. That is, a lithium transition metal composite oxide in which the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) is more than 1, and an active material in which no diffraction peak exists in the range of 20° or more and 22° or less in the above X-ray diffraction pattern has a large capacitance.

[0038] Note that the composition ratio of the lithium transition metal composite oxide in this specification refers to the composition ratio when it is in a fully discharged state by the following method. First, the non-aqueous electrolyte storage element is charged at a constant current with a current of 0.05C until the charging end voltage during normal use is reached to make it in a fully charged state. After a rest of 30 minutes, it is discharged at a constant current with a current of 0.05C to the lower limit voltage during normal use. It is disassembled, the positive electrode is taken out, a test battery is assembled with a metal lithium electrode as the counter electrode, and at a current value of 10 mA per 1 g of the positive electrode mixture, the positive electrode potential is 2.0V vs.Li / Li + and constant current discharge is performed until it becomes, and the positive electrode is adjusted to a fully discharged state. Here, for the metal lithium electrode, pure metal lithium is used instead of a lithium alloy. It is disassembled again and the positive electrode is taken out. Using dimethyl carbonate, the non-aqueous electrolyte attached to the taken-out positive electrode is thoroughly washed, dried at room temperature for one day and night, and the lithium transition metal composite oxide of the positive electrode active material is collected. The collected lithium transition metal composite oxide is subjected to measurement. The operations from the disassembly of the non-aqueous electrolyte storage element to the measurement are performed in an argon atmosphere with a dew point of -60°C or lower. Here, normal use means the case where the non-aqueous electrolyte storage element is used by adopting the charge and discharge conditions recommended or specified for the non-aqueous electrolyte storage element, and when a charger for the non-aqueous electrolyte storage element is prepared, it means the case where the non-aqueous electrolyte storage element is used by applying that charger.

[0039] X-ray diffraction measurement of the lithium transition metal composite oxide is performed on the lithium transition metal composite oxide in the fully discharged state by the above method. Specifically, the X-ray diffraction measurement is carried out by powder X-ray diffraction measurement using an X-ray diffractometer ("MiniFlex II" manufactured by Rigaku). The X-ray source is CuKα ray, the tube voltage is 30 kV, and the tube current is 15 mA. At this time, the diffracted X-ray passes through a Kβ filter with a thickness of 30 μm and is detected by a high-speed one-dimensional detector (D / teX Ultra 2). The sampling width is 0.02°, the scan speed is 5° / min, the divergence slit width is 0.625°, the receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm.

[0040] The lower limit of the content of the lithium transition metal composite oxide with respect to all the cathode active materials is preferably 50% by mass, more preferably 80% by mass, and still more preferably 95% by mass. The content of the lithium transition metal composite oxide with respect to all the cathode active materials may be 100% by mass.

[0041] The average particle size of the cathode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the cathode active material to be equal to or greater than the above lower limit, the production or handling of the cathode active material becomes easy. By setting the average particle size of the cathode active material to be equal to or less than the above upper limit, the electron conductivity of the cathode active material layer is improved. Here, the "average particle size" means a value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) based on the particle size distribution measured by the laser diffraction / scattering method for a dilution obtained by diluting the particles with a solvent conforms to JIS-Z-8825 (2013).

[0042] To obtain particles of the positive electrode active material in a predetermined shape, a pulverizer, a classifier, or the like is used. As the pulverization method, for example, a method using a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling air flow type jet mill, a sieve, or the like can be mentioned. During pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. As the classification method, a sieve, an air classifier, or the like is used as needed for both dry and wet processes.

[0043] As the content of the positive electrode active material in the positive electrode active material layer, 70% by mass or more and 98% by mass or less is preferable, 80% by mass or more and 97% by mass or less is more preferable, and 90% by mass or more and 96% by mass or less is even more preferable. By setting the content of the positive electrode active material within the above range, the electric capacity of the secondary battery can be increased.

[0044] The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such a conductive agent include carbonaceous materials; metals; conductive ceramics, etc. Examples of the carbonaceous material include graphite and carbon black. Examples of the type of carbon black include furnace black, acetylene black, ketjen black, etc. Among these, from the viewpoints of conductivity and coatability, carbonaceous materials are preferable. Among them, acetylene black and ketjen black are preferable. Examples of the shape of the conductive agent include powder form, sheet form, fiber form, etc.

[0045] The content of the conductive agent in the positive electrode active material layer is preferably 1% by mass or more and 40% by mass or less, and more preferably 2% by mass or more and 10% by mass or less. By setting the content of the conductive agent within the above range, the energy density of the secondary battery can be increased.

[0046] Examples of the binder include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0047] The content of the binder in the positive electrode active material layer is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less. By setting the content of the binder within the above range, the active material can be stably held.

[0048] Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has a functional group that reacts with lithium, it is preferably deactivated in advance by methylation or the like. In one aspect of the present invention, the thickener may preferably not be contained in the positive electrode active material layer.

[0049] The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, and mineral resource-derived substances or artificial products thereof such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica. In one aspect of the present invention, the filler may preferably not be contained in the positive electrode active material layer.

[0050] The positive electrode active material layer may contain typical non-metal elements such as B, N, P, F, Cl, Br, I, etc., typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, etc., and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W, etc. as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0051] (Negative electrode) The negative electrode has a negative electrode substrate and a negative electrode active material layer disposed directly or via an intermediate layer on the negative electrode substrate. The intermediate layer of the negative electrode can have the same configuration as the intermediate layer of the positive electrode.

[0052] The negative electrode substrate can have the same configuration as the positive electrode substrate. As the material, metals such as copper, nickel, stainless steel, nickel-plated steel, etc. or their alloys, carbonaceous materials, etc. are used, and copper or a copper alloy is preferred. That is, a copper foil is preferred as the negative electrode substrate. Examples of the copper foil include rolled copper foil, electrolytic copper foil, etc.

[0053] The average thickness of the negative electrode substrate is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, still more preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate within the above range, the strength of the negative electrode substrate can be increased while increasing the energy density per unit volume of the secondary battery.

[0054] The negative electrode active material layer contains metallic lithium. That is, the secondary battery of this embodiment is a lithium battery. Metallic lithium is a component that functions as a negative electrode active material. Metallic lithium may exist as pure metallic lithium consisting essentially of only lithium element, or may exist as a lithium alloy containing other metal elements. Examples of the lithium alloy include lithium-silver alloy, lithium-zinc alloy, lithium-calcium alloy, lithium-aluminum alloy, lithium-magnesium alloy, lithium-indium alloy, etc. The lithium alloy may contain a plurality of metal elements other than lithium.

[0055] The negative electrode active material layer may be a layer consisting essentially of only metallic lithium. The content of metallic lithium in the negative electrode active material layer may be 90% by mass or more, may be 99% by mass or more, or may be 100% by mass.

[0056] The negative electrode active material layer may be a metallic lithium foil or a lithium alloy foil. The negative electrode active material layer may be a non-porous layer (solid layer). The average thickness of the negative electrode active material layer is preferably 5 μm or more and 1,000 μm or less, more preferably 10 μm or more and 500 μm or less, and even more preferably 30 μm or more and 300 μm or less.

[0057] (Separator) The separator can be appropriately selected from known separators. As the separator, for example, a separator consisting of only a base material layer, a separator having a heat-resistant layer containing heat-resistant particles and a binder formed on one or both surfaces of the base material layer, etc. can be used. The base material layer of the separator may contain heat-resistant particles. Examples of the material of the base material layer of the separator include woven fabric, non-woven fabric, porous resin film, etc. Among these materials, a porous resin film is preferable from the viewpoint of strength, and a non-woven fabric is preferable from the viewpoint of the liquid retention property of the non-aqueous electrolyte. From the viewpoint of the shut-down function, polyolefins such as polyethylene and polypropylene are preferable as the material of the base material layer of the separator, and polyimides and aramids are preferable from the viewpoint of oxidation decomposition resistance. As the base material layer of the separator, a composite material of these resins may be used.

[0058] The heat-resistant particles contained in the heat-resistant layer and the base material layer preferably have a mass loss of 5% or less when heated from room temperature to 500 °C under the atmosphere, and more preferably have a mass loss of 5% or less when heated from room temperature to 800 °C under the atmosphere. Examples of materials with a mass loss of a predetermined value or less when heated include inorganic compounds. Examples of inorganic compounds include oxides such as iron oxide, silicon oxide, aluminum oxide, titanium oxide, barium titanate, zirconium oxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicate; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; nitrides such as aluminum nitride and silicon nitride; carbonates such as calcium carbonate; sulfates such as barium sulfate; sparingly soluble ionic crystals such as calcium fluoride and barium fluoride; covalent crystals such as silicon and diamond; and mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, mica, or artificial products thereof. As the inorganic compound, these substances may be used alone as a simple substance or a composite, or two or more of them may be mixed and used. Among these inorganic compounds, from the viewpoint of the safety of the energy storage element, silicon oxide, aluminum oxide, or aluminosilicate is preferable.

[0059] From the viewpoint of strength, the porosity of the separator is preferably 80% by volume or less, and from the viewpoint of discharge performance, it is preferably 20% by volume or more. Here, the "porosity" is a value based on volume and means the measured value by a mercury porosimeter.

[0060] As the separator, a polymer gel composed of a polymer and a non-aqueous electrolyte may be used. Examples of the polymer include polyacrylonitrile, polyethylene oxide, polypropylene oxide, polyethylene carbonate, polypropylene carbonate, polyvinyl carbonate, polyalkyl methacrylates such as polymethyl methacrylate, polyalkyl acrylates such as polymethyl acrylate, polyvinyl ethylene carbonate, polyvinyl acetate, polyvinyl pyrrolidone, polymaleic acid and its derivatives, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, etc., and copolymers of monomers constituting these polymers, and mixtures of these polymers. Further, these polymers may be combined with inorganic salts or ionic liquids. When using a polymer gel, there is an effect of suppressing liquid leakage. As the separator, a porous resin film or non-woven fabric as described above and a polymer gel may be used in combination.

[0061] (Non-aqueous electrolyte) The non-aqueous electrolyte contains a polyvalent metal cation and an imide anion. The non-aqueous electrolyte usually further contains a non-aqueous solvent and an electrolyte salt dissolved in this non-aqueous solvent. The polyvalent metal cation and the imide anion may be added to or contained in the non-aqueous electrolyte as an additive (polyvalent metal imide salt) composed of these. Further, the polyvalent metal cation and the imide anion may exist in a state where some or all of them form an ion pair, may exist in a state of partially dissociated multiple ions, or may exist in a completely dissociated state. The imide anion may include those derived from the electrolyte salt. The non-aqueous electrolyte may further contain other additives and the like.

[0062] (Polyvalent metal cation) Examples of the polyvalent metal cation include polyvalent cations of metal elements among the elements of Group 2 to Group 14. The valence of the polyvalent metal cation may be divalent, trivalent or tetravalent or higher, but is preferably divalent or trivalent, and more preferably divalent. The polyvalent metal cation may be contained singly or in combination of two or more.

[0063] Specific polyvalent metal cations include polyvalent cations of Group 2 elements (Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , etc.), polyvalent cations of Group 3 elements (Sc 3+ , La 3+ , etc.), polyvalent cations of Group 4 elements (Ti 3+ , etc.), polyvalent cations of Group 5 elements (V 3+ , etc.), polyvalent cations of Group 6 elements (Cr 3+ , etc.), polyvalent cations of Group 7 elements (Mn 2+ , etc.), polyvalent cations of Group 8 elements (Fe 2+ , Fe 3+ , etc.), polyvalent cations of Group 9 elements (Co 2+ , etc.), polyvalent cations of Group 10 elements (Ni 2+ , etc.), polyvalent cations of Group 11 elements (Cu 2+ , etc.), polyvalent cations of Group 12 elements (Zn 2+ , Cd 2+ , etc.), polyvalent cations of metal elements among Group 13 elements (Al 3+ , etc.), polyvalent cations of metal elements among Group 14 elements (Sn 2+ , Pb 2+ , etc.), and the like.

[0064] Among these, polyvalent cations of Group 2 elements, Group 3 elements, Group 11 elements or Group 12 elements are preferable, polyvalent cations of Group 2 elements, Group 11 elements or Group 12 elements are more preferable, polyvalent cations of Group 2 elements or Group 11 elements are even more preferable, and magnesium ions (Mg 2+ ) and copper ions (Cu 2+ ) are even more preferable. Further, it is also preferable that the polyvalent metal cation is an element of the third period or the fourth period. By containing such a polyvalent metal cation in the non-aqueous electrolyte, the effect of suppressing the occurrence of micro short circuits accompanying repeated charge and discharge is enhanced.

[0065] The polyvalent metal cation is preferably a cation of a typical element. A typical element refers to an element other than a transition metal element (Group 3 to Group 11 elements). That is, examples of the polyvalent metal cation that is a cation of a typical element include polyvalent cations of Group 2 elements and Group 12 elements, and polyvalent cations of metal elements among Group 13 elements, Group 14 elements, and Group 15 elements.

[0066] The content of the polyvalent metal cation in the non-aqueous electrolyte is preferably 0.0001% by mass or more and 1% by mass or less, more preferably 0.001% by mass or more and 0.1% by mass or less, and still more preferably 0.002% by mass or more and 0.03% by mass or less. Also, the content of the polyvalent metal cation in the non-aqueous electrolyte is preferably 0.01 mmol / kg or more and 100 mmol / kg or less, more preferably 0.1 mmol / kg or more and 10 mmol / kg or less, and still more preferably 0.5 mmol / kg or more and 4 mmol / kg or less. When the content of the polyvalent cation is at least the above lower limit, a film of sufficient amount and quality is formed, and the effect of suppressing the occurrence of micro short circuits accompanying repeated charge and discharge is enhanced. On the other hand, when the content of the polyvalent cation is at most the above upper limit, the solubility and conductivity of lithium ions can be maintained in a sufficient state, the effect of suppressing the occurrence of micro short circuits accompanying repeated charge and discharge is enhanced, and the charge and discharge performance is also improved.

[0067] (Imide anion) Examples of the imide anion include N(SO2F)2 - (Bis(fluorosulfonyl)imide anion: FSI - ), N(CF3SO2)2 - (Bis(trifluoromethanesulfonyl)imide anion: TFSI - ), N(C2F5SO2)2 - (Bis(pentafluoroethanesulfonyl)imide anion: BETI - ), N(C4F9SO2)2 - (Bis(nonafluorobutanesulfonyl)imide anion), CF3-SO2-N-SO2-N-SO2-CF3 - , CF3-SO2-N-SO2-CF2-SO2-N-SO2-CF3 2-Symmetric sulfonylimide anions such as N(SO2F)(SO2CF3) - ((Fluorosulfonyl)(trifluoromethanesulfonyl)imide anion), N(SO2F)(SO2C2F5) - ((Fluorosulfonyl)(pentafluoroethanesulfonyl)imide anion), N(SO2F)(SO2C4F9) - ((Fluorosulfonyl)(nonafluorobutanesulfonyl)imide anion), N(SO2CF3)(SO2C4F9) - ((Trifluoromethanesulfonyl)(nonafluorobutanesulfonyl)imide anion), FSO2-N-SO2-C4F9 - , CF3-SO2-N-SO2-C4F9 - , CF3-SO2-N-SO2-CF2-SO3 2- , CF3-SO2-N-SO2-CF2-SO2-C(-SO2CF3)2 2- Asymmetric sulfonylimide anions such as N(POF2)2 - Phosphonylimide anions such as (bis(difluorophosphonyl)imide anion) can be mentioned, and sulfonylimide anions (symmetric sulfonylimide anions and asymmetric sulfonylimide anions) are preferred. One or more imide anions can be used.

[0068] The imide anion preferably has a fluorine atom, and specifically, for example, preferably has a fluorosulfonyl group, a difluorophosphonyl group, a fluoroalkyl group, etc. Further, as the imide anion, a sulfonylimide anion having a fluorine atom is more preferred, and bis(trifluoromethanesulfonyl)imide anion (TFSI - ) is particularly preferred. By using such an imide anion, the occurrence of micro short circuits can be more suppressed, for example, because the formed film becomes of better quality.

[0069] The content of the imide anion in the non-aqueous electrolyte is preferably 0.001% by mass or more and 50% by mass or less, more preferably 0.005% by mass or more and 10% by mass or less, still more preferably 0.01% by mass or more and 3% by mass or less, even more preferably 0.02% by mass or more and 1% by mass or less, and particularly preferably 0.03% by mass or more and 0.2% by mass or less. Further, the content of the imide anion in the non-aqueous electrolyte is preferably 0.02 mmol / kg or more and 3 mol / kg or less, more preferably 0.1 mmol / kg or more and 1 mol / kg or less, still more preferably 0.2 mmol / kg or more and 200 mmol / kg or less, even more preferably 0.5 mmol / kg or more and 20 mmol / kg or less, and particularly preferably 1 mmol / kg or more and 8 mmol / kg or less. When the content of the imide anion is not less than the above lower limit, a sufficient amount and quality of the film are formed, and the effect of suppressing the occurrence of micro short circuits accompanying repeated charge and discharge is enhanced. On the other hand, when the content of the imide anion is not more than the above upper limit, the conductivity can be maintained in a sufficient state, the effect of suppressing the occurrence of micro short circuits accompanying repeated charge and discharge is enhanced, and the charge and discharge performance is also improved. In the case where the imide anion in the non-aqueous electrolyte is, for example, added or contained in the non-aqueous electrolyte as a polyvalent metal imide salt and contained in the non-aqueous electrolyte as an electrolyte salt, it is the total of the content of the imide anion derived from these polyvalent metal imide salts and the content of the imide anion derived from the electrolyte salt.

[0070] (Polyvalent metal imide salt) As described above, the polyvalent metal cation and the imide anion may be added or contained in the non-aqueous electrolyte as an additive composed of these, that is, a polyvalent metal imide salt. One or more polyvalent metal imide salts can be used.

[0071] Examples of the polyvalent metal imide salts include Mg(TFSI)2, Ca(TFSI)2, La(TFSI)3, Ti(TFSI)3, Mn(TFSI)2, Cu(TFSI)2, Zn(TFSI)2, Al(TFSI)3, Mg(FSI)2, Ca(FSI)2, La(FSI)3, Ti(FSI)3, Mn(FSI)2, Cu(FSI)2, Zn(FSI)2, Al(FSI)3, Mg(BETI)2, Mg(N(POF2)2)2, and the like.

[0072] The addition amount of the polyvalent metal imide salt to the non-aqueous electrolyte is preferably 0.001% by mass or more and 3% by mass or less, more preferably 0.01% by mass or more and 0.5% by mass or less, and even more preferably 0.03% by mass or more and 0.2% by mass or less. Also, the addition amount of the polyvalent metal imide salt to the non-aqueous electrolyte is preferably 0.01 mmol / kg or more and 100 mmol / kg or less, more preferably 0.1 mmol / kg or more and 10 mmol / kg or less, and even more preferably 0.5 mmol / kg or more and 4 mmol / kg or less.

[0073] (Non-aqueous solvent) The non-aqueous solvent can be appropriately selected from known non-aqueous solvents. Examples of the non-aqueous solvent include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphate esters, sulfonic acid esters, ethers, amides, nitriles, etc. As the non-aqueous solvent, those in which some of the hydrogen atoms contained in these compounds are substituted with halogens may be used.

[0074] As the non-aqueous solvent, it is preferable to use at least one of cyclic carbonate and chain carbonate, and it is more preferable to use cyclic carbonate and chain carbonate in combination. By using cyclic carbonate, the dissociation of the electrolyte salt can be promoted and the ionic conductivity of the non-aqueous electrolyte can be improved. By using chain carbonate, the viscosity of the non-aqueous electrolyte can be kept low. When cyclic carbonate and chain carbonate are used in combination, the volume ratio of cyclic carbonate to chain carbonate (cyclic carbonate: chain carbonate) is preferably in the range of, for example, 5:95 to 50:50.

[0075] Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (including trans-form, cis-form, and mixtures thereof), 4-(fluoromethyl)-1,3-dioxolan-2-one, 4-(difluoromethyl)-1,3-dioxolan-2-one, trifluoropropyl carbonate, 4-(trifluoroethyl)-1,3-dioxolan-2-one, styrene carbonate, catechol carbonate, phenyl vinylene carbonate, 1,2-diphenyl vinylene carbonate, and the like. The number of carbon atoms of the cyclic carbonate may be, for example, 3 or more and 13 or less, and may also be 7 or less or 5 or less.

[0076] From the viewpoint of oxidation resistance and the like, fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), difluoroethylene carbonate, 4-(fluoromethyl)-1,3-dioxolan-2-one, 4-(difluoromethyl)-1,3-dioxolan-2-one, trifluoropropyl carbonate, 4-(trifluoroethyl)-1,3-dioxolan-2-one, and the like are preferable as the cyclic carbonate.

[0077] Examples of the chain carbonate include diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, phenyl methyl carbonate, diphenyl carbonate, trifluoromethyl ethyl carbonate, 2,2,2-trifluoroethyl methyl carbonate (TFEMC), bis(trifluoromethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, ethyl-2,2,2-trifluoroethyl carbonate, and the like. The number of carbon atoms of the chain carbonate may be, for example, 3 or more and 13 or less, and may also be 7 or less or 5 or less.

[0078] As the chain carbonate, from the viewpoint of oxidation resistance and the like, fluorinated chain carbonates such as 2,2,2-trifluoroethyl methyl carbonate (TFEMC), bis(2,2,2-trifluoroethyl) carbonate, and ethyl-2,2,2-trifluoroethyl carbonate are preferable.

[0079] The content of carbonate in all non-aqueous solvents is preferably 50% by volume or more and 100% by volume or less, more preferably 80% by volume or more, and may be further preferably 90% by volume or more, 95% by volume or more, or 99% by volume or more in some cases.

[0080] The non-aqueous solvent preferably contains a fluorinated solvent. The total content of the fluorinated solvent in all non-aqueous solvents is preferably 60% by volume or more, more preferably 90% by volume or more, further preferably 99% by volume or more, and particularly preferably 100% by volume. The fluorinated solvent refers to a solvent (non-aqueous solvent) having a fluorine atom in the molecule, such as fluorinated carbonate (fluorinated chain carbonate and fluorinated cyclic carbonate), fluorinated ether, etc. By containing such a fluorinated solvent, preferably in an amount not less than the above lower limit, it is possible to further enhance the suppression of micro short-circuit, oxidation resistance, etc.

[0081] (Electrolyte salt) The electrolyte salt is usually a lithium salt. Examples of lithium salts include inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, LiN(SO2F)2, etc., and organic lithium salts such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, LiC(SO2C2F5)3, etc. Inorganic lithium salts refer to lithium salts that do not contain carbon atoms in the anion, and organic lithium salts refer to lithium salts that contain carbon atoms in the anion. The organic lithium salt preferably has a halogenated hydrocarbon group, more preferably has a fluorinated hydrocarbon group, and even more preferably has a fluoroalkyl group. The electrolyte salt may be an imide salt or an electrolyte salt other than the imide salt. As the electrolyte salt, an inorganic lithium salt or a salt containing a phosphorus atom in the anion is preferred, and LiPF6 is more preferred. Also, from the viewpoints of oxidation resistance and good film formation, etc., the electrolyte salt preferably contains a fluorine atom.

[0082] The content of the electrolyte salt (excluding polyvalent metal imide salts) in the non-aqueous electrolyte is preferably 0.1 mol / dm 3 or more and 2.5 mol / dm 3 or less, more preferably 0.3 mol / dm 3 or more and 2.0 mol / dm 3 or less, even more preferably 0.5 mol / dm 3 or more and 1.7 mol / dm 3 or less, particularly preferably 0.7 mol / dm 3 or more and 1.5 mol / dm 3 or less. By setting the content of the electrolyte salt within the above range, the ionic conductivity of the non-aqueous electrolyte can be increased.

[0083] The non-aqueous electrolyte may contain other additives. Examples of the other additives include aromatic compounds such as biphenyl, alkyl biphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, dibenzofuran; partial halides of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; ethylene sulfite, propylene sulfite, dimethyl sulfite, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfone, dimethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, thioanisole, diphenyl disulfide, dipyridinium disulfide, perfluorooctane, tris(trimethylsilyl) borate, tris(trimethylsilyl) phosphite, tris(trimethylsilyl) phosphate, tetrakis(trimethylsilyl) titanate, etc. These additives may be used alone or in combination of two or more.

[0084] The content of other additives (excluding polyvalent metal imide salts) contained in the non-aqueous electrolyte is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 7% by mass or less, still more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.3% by mass or more and 3% by mass or less, based on the total non-aqueous electrolyte. By setting the content of the additive within the above range, the capacity retention performance or charge-discharge cycle performance after high-temperature storage can be improved, or the safety can be further improved.

[0085] In the secondary battery (non-aqueous electrolyte storage element), the positive electrode potential at the end-of-charge voltage during normal use is preferably 4.30 V vs. Li / Li + or higher, and 4.35 V vs. Li / Li +More preferably, it is as described above, 4.40V vs. Li / Li + In some cases, it may be even more preferable that it is as described above. By setting the positive electrode potential at the charging cut-off voltage during normal use to be equal to or higher than the above lower limit, the discharge capacity can be increased and the energy density can be enhanced.

[0086] Note that "during normal use" refers to the case where the non-aqueous electrolyte storage element is used by adopting the charging conditions recommended or specified for the non-aqueous electrolyte storage element. For example, when a charger for the non-aqueous electrolyte storage element is prepared, it refers to the case where the non-aqueous electrolyte storage element is used by applying that charger.

[0087] As the upper limit of the positive electrode potential at the charging cut-off voltage during normal use of the secondary battery, for example, 5.0V vs. Li / Li + or 4.8V vs. Li / Li + is also possible, or 4.7V vs. Li / Li + is also possible, or 4.6V vs. Li / Li + is also possible.

[0088] Dendrites tend to grow easily when the current density during charging is high. Therefore, the non-aqueous electrolyte storage element according to an embodiment of the present invention can be suitably applied to applications where charging with a high current density is performed. Such applications include power sources for automobiles such as electric vehicles (EVs), hybrid vehicles (HEVs), plug-in hybrid vehicles (PHEVs), and power sources for regenerative power charging.

[0089] The shape of the non-aqueous electrolyte storage element of this embodiment is not particularly limited, and examples include cylindrical batteries, laminated film batteries, square batteries, flat batteries, coin-type batteries, button-type batteries, and the like.

[0090] FIG. 1 shows a non-aqueous electrolyte storage element 1 as an example of a rectangular battery. Note that this figure is a perspective view of the interior of the container. An electrode body 2 having a positive electrode and a negative electrode wound with a separator interposed therebetween is housed in a rectangular container 3. The positive electrode is electrically connected to a positive electrode terminal 4 via a positive electrode lead 41. The negative electrode is electrically connected to a negative electrode terminal 5 via a negative electrode lead 51.

[0091] <Configuration of Non-Aqueous Electrolyte Storage Device> The non-aqueous electrolyte storage element of the present embodiment can be mounted as a power storage unit (battery module) configured by aggregating a plurality of non-aqueous electrolyte storage elements in a power source for automobiles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), a power source for electronic devices such as personal computers and communication terminals, or a power source for power storage. In this case, the technology according to an embodiment of the present invention may be applied to at least one non-aqueous electrolyte storage element included in the power storage unit.

[0092] FIG. 2 shows an example of a power storage device 30 in which power storage units 20 in which two or more non-aqueous electrolyte storage elements 1 electrically connected are further aggregated. The power storage device 30 may include a bus bar (not shown) for electrically connecting two or more non-aqueous electrolyte storage elements 1, a bus bar (not shown) for electrically connecting two or more power storage units 20, and the like. The power storage unit 20 or the power storage device 30 may include a state monitoring device (not shown) for monitoring the state of one or more non-aqueous electrolyte storage elements.

[0093] <Manufacturing Method of Non-Aqueous Electrolyte Storage Element> The manufacturing method of the non-aqueous electrolyte storage element according to an embodiment of the present invention includes preparing a negative electrode containing metallic lithium and preparing a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion.

[0094] Preparing a negative electrode containing metallic lithium may be to fabricate a negative electrode containing metallic lithium. The fabrication of the negative electrode can be carried out by laminating a negative electrode active material layer containing metallic lithium directly on the negative electrode substrate or via an intermediate layer, and then pressing or the like. The negative electrode active material layer containing metallic lithium may be a metallic lithium foil or a lithium alloy foil. The specific form and preferred form of the prepared negative electrode can apply the forms described above as the negative electrode provided in the non-aqueous electrolyte storage element.

[0095] Preparing a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion may be to prepare a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion. The preparation of the non-aqueous electrolyte can be carried out, for example, by adding components other than the non-aqueous solvent, such as a polyvalent metal imide salt composed of a polyvalent metal cation and an imide anion, an electrolyte salt, etc., to the non-aqueous solvent and mixing them. The specific form and preferred form of the prepared non-aqueous electrolyte can apply the forms described above as the non-aqueous electrolyte provided in the non-aqueous electrolyte storage element.

[0096] For example, the manufacturing method of the non-aqueous electrolyte storage element includes preparing or fabricating a positive electrode, preparing or fabricating a negative electrode, preparing or preparing a non-aqueous electrolyte, preparing or fabricating a separator, forming an electrode body in which the positive electrode and the negative electrode are alternately stacked by laminating or winding them with a separator in between, housing the positive electrode and the negative electrode (electrode body) in a container, and injecting the non-aqueous electrolyte into the container. After injection, the injection port can be sealed to obtain the non-aqueous electrolyte storage element.

[0097] The method for manufacturing the non-aqueous electrolyte storage element may further include performing initial charge and discharge on the assembled non-charged and discharged storage element. For example, when a lithium transition metal composite oxide in which the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) in the positive electrode active material of the non-aqueous electrolyte storage element is greater than 1 is used, the capacity increases through the initial charge and discharge. The number of charge and discharge cycles in the initial charge and discharge may be 1 or 2, or may be 3 or more. When a lithium transition metal composite oxide in which the molar ratio of lithium (Li) to transition metal (Me) (Li / Me) in the positive electrode active material of the non-aqueous electrolyte storage element is greater than 1 is used, the positive electrode potential (positive electrode reaching potential) at the charge cut-off voltage in the initial charge and discharge is 4.5V vs. Li / Li + to 4.7V vs. Li / Li + or less is preferable.

[0098] <Non-aqueous electrolyte> The non-aqueous electrolyte according to one embodiment of the present invention is a non-aqueous electrolyte for a lithium battery containing a polyvalent metal cation and an imide anion. A lithium battery is a secondary battery in which metallic lithium (pure metallic lithium or a lithium alloy) is used as the negative electrode active material. That is, specific forms and preferred forms of the non-aqueous electrolyte include those described above as the non-aqueous electrolyte constituting the non-aqueous electrolyte storage element according to one embodiment of the present invention.

[0099] <Other embodiments> The present invention is not limited to the above embodiments, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of a certain embodiment, and a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment or well-known technology. Further, a part of the configuration of a certain embodiment can be deleted. Also, well-known technology can be added to the configuration of a certain embodiment.

[0100] In the above embodiment, the case where the non-aqueous electrolyte storage element is used as a non-aqueous electrolyte secondary battery (lithium battery) capable of charge and discharge has been described. However, the type, shape, dimensions, capacity, etc. of the non-aqueous electrolyte storage element are arbitrary. The non-aqueous electrolyte storage element of the present invention can also be applied to various non-aqueous electrolyte secondary batteries, electric double layer capacitors, or capacitors such as lithium ion capacitors.

Examples

[0101] Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the following examples.

[0102] [Example 1] (Fabrication of positive electrode) As the positive electrode active material, a lithium transition metal composite oxide having an α-NaFeO2 type crystal structure and represented by Li 1+α Me 1-α O2 (Me is a transition metal) was used. Here, the molar ratio of Li to Me, Li / Me, was 1.33, and Me consisted of Ni and Mn and contained them in a molar ratio of Ni:Mn = 1:2.

[0103] Using N-methylpyrrolidone (NMP) as a dispersion medium, a positive electrode paste containing the above positive electrode active material, acetylene black (AB) as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 94:4.5:1.5 was prepared. The positive electrode paste was applied to one side of an aluminum foil which is a positive electrode substrate, dried and then pressed to produce a positive electrode in which a positive electrode active material layer was disposed on one side of the positive electrode substrate.

[0104] (Fabrication of negative electrode) A metal lithium foil (pure metal lithium of 100% by mass of metal lithium) was laminated on one side of a copper foil which is a negative electrode substrate and then pressed to produce a negative electrode. Note that the positive electrode and the negative electrode were designed and fabricated so that the current density at 1C was 5.0 mA / cm 2 to be.

[0105] (Preparation of non-aqueous electrolyte) LiPF6 was dissolved in a mixed solvent obtained by mixing fluoroethylene carbonate (FEC) and 2,2,2-trifluoroethyl methyl carbonate (TFEMC) at a volume ratio of 30:70 to a concentration of 1 mol / dm 3 and further Mg(TFSI)2 was added as an additive at 0.1 mass% (Mg 2+ : 0.0042 mass%, 1.7 mmol / kg, TFSI - : 0.096 mass%, 3.4 mmol / kg) and dissolved to obtain a non-aqueous electrolyte.

[0106] (Fabrication of non-aqueous electrolyte energy storage device) An electrode body was fabricated by laminating the above positive electrode and the above negative electrode through a separator which is a polyolefin microporous membrane. This electrode body was housed in a container made of a metal-resin composite film, the above non-aqueous electrolyte was injected therein, and then sealed by heat welding to obtain the non-aqueous electrolyte energy storage device (laminated lithium battery) of Example 1.

[0107] [Examples 2 to 5 and Comparative Examples 1 to 4] Each non-aqueous electrolyte energy storage device of Examples 2 to 5 and Comparative Examples 1 to 4 was obtained in the same manner as in Example 1, except that the additive described in Table 1 was used at 0.1 mass% instead of Mg(TFSI)2 as the additive, or no additive was added.

[0108] (Initial charge and discharge) For each of the obtained non-aqueous electrolyte energy storage devices, initial charge and discharge were performed under the following conditions. At 25°C, constant current and constant voltage charging was performed with a charging charge of 0.1C and a charging cut-off voltage of 4.6V. The end condition of charging was until the charging current reached 0.05C. Thereafter, a rest period of 10 minutes was provided. Thereafter, constant current discharge was performed with a discharge current of 0.1C and a discharge cut-off voltage of 2.0V, and then a rest period of 10 minutes was provided. This charge and discharge cycle was performed 2 cycles.

[0109] (Charge and discharge cycle test) Next, the following charge-discharge cycle test was conducted. At 25°C, constant current-constant voltage charging was performed with a charging current of 0.2C and a charging cut-off voltage of 4.6V. The end condition of charging was until the charging current reached 0.05C. Thereafter, a 10-minute rest period was provided. Then, constant current discharge was performed with a discharge current of 0.1C and a discharge cut-off voltage of 2.0V, and thereafter, a 10-minute rest period was provided. This charge-discharge cycle was repeated, and the number of cycles until a micro short circuit occurred was recorded. The results (number of cycles until a micro short circuit occurred) are shown in Table 1.

[0110]

Table 1

[0111] As shown in Table 1, each non-aqueous electrolyte storage element of Examples 1 to 5 in which a polyvalent metal imide salt was added, that is, a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion was used, had more than 70 cycles until a micro short circuit occurred, and an excellent effect of suppressing the occurrence of a micro short circuit accompanying repeated charge and discharge was confirmed. On the other hand, in each non-aqueous electrolyte storage element of Comparative Examples 2 and 3 to which a monovalent metal imide salt was added and Comparative Example 4 to which another salt was added, an effect of suppressing the occurrence of a micro short circuit accompanying sufficient repeated charge and discharge could not be confirmed.

Industrial Applicability

[0112] The present invention can be applied to non-aqueous electrolyte storage elements used as power sources for electronic devices such as personal computers and communication terminals, and automobiles.

Explanation of Symbols

[0113] 1 Non-aqueous electrolyte storage element 2 Electrode body 3 Container 4 Positive electrode terminal 41 Positive electrode lead 5 Negative electrode terminal 51 Negative electrode lead 20 Power storage unit 30 Power storage device

Claims

1. A positive electrode containing a lithium transition metal composite oxide having an α-NaFeO 2 type crystal structure; A negative electrode containing metallic lithium, and Nonaqueous electrolyte containing polyvalent metal cations and imide anions A non-aqueous electrolyte electricity storage element comprising:

2. Providing a positive electrode containing a lithium transition metal composite oxide having an α-NaFeO 2 type crystal structure; Providing a negative electrode containing metallic lithium; and Providing a non-aqueous electrolyte containing a polyvalent metal cation and an imide anion. A method for manufacturing a nonaqueous electrolyte storage element comprising the steps of:

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