Non-aqueous electrolyte energy storage device and method for manufacturing the same

Abstract

To provide a nonaqueous electrolyte power storage device which is high in the capacity-keeping rate in a charge / discharge cycle, and which is arranged so that the rise in resistance can be suppressed, a method for manufacturing such a nonaqueous electrolyte power storage device.SOLUTION: A nonaqueous electrolyte power storage device 1 comprises: a negative electrode containing a negative electrode active material; and a nonaqueous electrolyte containing an additive agent. In the nonaqueous electrolyte power storage device, a coating that contains a sulfur element is formed on the surface of the negative electrode. The additive agent is a compound containing a sulfur element. The concentration of the additive agent in the nonaqueous electrolyte is 0.2 mass% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

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

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. The non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically separated 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 popular.

[0003] In order to improve the performance of non-aqueous electrolyte storage elements, conventionally, various additives have been studied to be added to non-aqueous electrolytes. Patent Document 1 describes a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte containing a cyclic sulfate ester.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In non-aqueous electrolyte storage elements, it is desirable that the initial performance be maintained for a long time even when the charge and discharge cycles are repeated. In particular, a high capacity retention rate and suppression of resistance increase in the charge and discharge cycles are required. However, in conventional non-aqueous electrolyte storage elements, it is difficult to achieve both of these.

[0006] The present invention has been made based on the above circumstances, and an object thereof is to provide a non-aqueous electrolyte storage element having a high capacity retention rate and suppressed resistance increase in charge and discharge cycles, and a method for manufacturing such a non-aqueous electrolyte storage element.

Means for Solving the Problems

[0007] One aspect of the present invention includes a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, a film containing sulfur element is formed on the surface of the negative electrode, the additive is a compound containing sulfur element, and the concentration of the additive in the non-aqueous electrolyte is 0.2% by mass or less. It is a non-aqueous electrolyte storage element.

[0008] Another aspect of the present invention includes assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and initially charging and discharging the uncharged and discharged storage element, wherein the additive is a compound containing sulfur element, and it is a method for manufacturing a non-aqueous electrolyte storage element that satisfies the following formula 1. 0.004 ≦ m S / m N ≦ 0.016 ··· 1 In formula 1, m S is the mass (g) of the additive contained in the non-aqueous electrolyte. m N is the mass (g) of the negative electrode active material contained in the negative electrode.

[0009] Another aspect of the present invention includes assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and initially charging and discharging the uncharged and discharged storage element, wherein the additive is a compound containing sulfur element, and it is a method for manufacturing a non-aqueous electrolyte storage element that satisfies the following formula 2. 0.010 ≦ m S / c N ≦ 0.048 ··· 2 In formula 2, m S is the mass (g) of the additive contained in the non-aqueous electrolyte. c N is the discharge capacity (Ah) of the negative electrode.

Effects of the Invention

[0010] According to one aspect of the present invention, it is possible to provide a non-aqueous electrolyte storage element having a high capacity retention rate in a charge / discharge cycle and suppressed resistance increase, and a method for manufacturing such a non-aqueous electrolyte storage element.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0012] First, an overview of the non-aqueous electrolyte storage element and the method for manufacturing the non-aqueous electrolyte storage element disclosed by this specification will be described.

[0013] A non-aqueous electrolyte storage element according to one aspect of the present invention includes a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive. A film containing sulfur element is formed on the surface of the negative electrode. The additive is a compound containing sulfur element, and the concentration of the additive in the non-aqueous electrolyte is 0.2 mass% or less.

[0014] The non-aqueous electrolyte storage element according to one aspect of the present invention has a high capacity retention rate and suppressed resistance increase during charge-discharge cycles. The reason for this is not clear, but the following reasons are speculated. In the non-aqueous electrolyte storage element, an additive is contained in the non-aqueous electrolyte, the additive is a compound containing sulfur element, and a film containing sulfur element is formed on the surface of the negative electrode, so that the capacity retention rate during charge-discharge cycles is high. When manufacturing a non-aqueous electrolyte storage element using the non-aqueous electrolyte containing the above additive, a part of the additive decomposes during the initial charge-discharge to form a film on the negative electrode surface. However, the inventors have found that when the concentration of the additive remaining in the non-aqueous electrolyte after the initial charge-discharge exceeds 0.2% by mass, the remaining additive mainly has an adverse effect on the positive electrode, etc., resulting in an increase in resistance during charge-discharge cycles. Therefore, in the non-aqueous electrolyte storage element, by setting the concentration of the additive in the non-aqueous electrolyte to 0.2% by mass or less, the unfavorable influence mainly exerted on the positive electrode is suppressed, and it is presumed that the increase in resistance during charge-discharge cycles is suppressed.

[0015] Note that the concentration of the additive in the non-aqueous electrolyte provided in the non-aqueous electrolyte storage element according to one aspect of the present invention is not the concentration of the additive in the non-aqueous electrolyte used during manufacturing, but the concentration of the additive in the non-aqueous electrolyte provided in the completed non-aqueous electrolyte storage element. Usually, as described above, after assembling the non-aqueous electrolyte storage element, it is completed by performing initial charge-discharge, and during the initial charge-discharge, a part of the additive is consumed for film formation. For this reason, the concentration of the additive in the non-aqueous electrolyte provided in the completed non-aqueous electrolyte storage element has decreased from the concentration of the non-aqueous electrolyte used during manufacturing. The above initial charge-discharge may be performed, for example, for capacity confirmation after assembling an uncharged and discharged storage element, or for activating a specific positive electrode active material, etc., and refers to the charge-discharge performed until the non-aqueous electrolyte storage element as a completed product is shipped or used.

[0016] It is preferable that the concentration of the additive in the non-aqueous electrolyte is 0.01% by mass or more. There is a certain degree of correlation between the concentration of the additive in the non-aqueous electrolyte before the initial charge and discharge used in the manufacturing and the concentration of the additive remaining in the non-aqueous electrolyte of the completed non-aqueous electrolyte storage element. Therefore, if the concentration of the additive remaining in the non-aqueous electrolyte of the completed non-aqueous electrolyte storage element is 0.01% by mass or more, it can be said that the non-aqueous electrolyte used in the manufacturing contained an additive at a sufficient concentration to form a film containing a sufficient amount of sulfur element on the surface of the negative electrode. In this case, the capacity retention rate in the charge and discharge cycles of the non-aqueous electrolyte storage element is further increased.

[0017] It is preferable that the additive is a compound containing a sulfonyl group structure. When such an additive is used, a good film is formed on the surface of the negative electrode, and the adverse effects on the positive electrode and the like are small, so that the capacity retention rate in the charge and discharge cycles of the non-aqueous electrolyte storage element is further increased and the increase in resistance is further suppressed.

[0018] It is preferable that the additive is sulfates. When such an additive is used, a better film is formed on the surface of the negative electrode, and the adverse effects on the positive electrode and the like are smaller, so that the capacity retention rate in the charge and discharge cycles of the non-aqueous electrolyte storage element is further increased and the increase in resistance is further suppressed.

[0019] The non-aqueous electrolyte storage element according to one aspect of the present invention preferably further includes a positive electrode containing a polyanion compound. Although the polyanion compound can be used as a positive electrode active material with a high capacity retention rate, when the additive is a compound containing a sulfur element, the additive remaining in the non-aqueous electrolyte and its decomposition products are likely to elute the transition metal in the polyanion compound and cause an increase in resistance. Therefore, when the non-aqueous electrolyte storage element includes a positive electrode containing a polyanion compound, the effect of suppressing the increase in resistance in the charge and discharge cycles can be particularly sufficiently enjoyed.

[0020] The manufacturing method of a non-aqueous electrolyte storage element according to one aspect of the present invention includes assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element. The additive is a compound containing a sulfur element, and it is a manufacturing method (α) of a non-aqueous electrolyte storage element that satisfies the following formula 1. 0.004 ≦ m S / m N ≦ 0.016 ··· 1 In formula 1, m S is the mass (g) of the additive contained in the non-aqueous electrolyte. m N is the mass (g) of the negative electrode active material contained in the negative electrode.

[0021] According to the manufacturing method (α), a non-aqueous electrolyte storage element with a high capacity retention rate and suppressed resistance increase in the charge and discharge cycle can be manufactured. The reason for this is not clear, but the following reasons are speculated. The amount of the additive consumed in the initial charge and discharge has a high correlation with the mass of the negative electrode active material. In the manufacturing method (α), by satisfying the above formula 1, a non-aqueous electrolyte storage element in which a film containing a sulfur element is sufficiently formed on the surface of the negative electrode and the remaining amount of the additive in the non-aqueous electrolyte is small is obtained, and it is speculated that the above effects are achieved.

[0022] The manufacturing method of a non-aqueous electrolyte storage element according to another aspect of the present invention includes assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element. The additive is a compound containing a sulfur element, and it is a manufacturing method of a non-aqueous electrolyte storage element that satisfies the following formula 2. 0.010 ≦ m S / c N ≦ 0.048 ··· 2 In formula 2, m S is the mass (g) of the additive contained in the non-aqueous electrolyte. c N is the discharge capacity (Ah) of the negative electrode.

[0023] According to the manufacturing method (β), a non-aqueous electrolyte storage element with a high capacity retention rate in charge-discharge cycles and suppressed resistance increase can be manufactured. The reason for this is not clear, but the following reasons are speculated. The amount of the additive consumed in the initial charge-discharge is highly correlated with the discharge capacity of the negative electrode in addition to the mass of the above-mentioned negative electrode active material. Therefore, in the manufacturing method (β), by satisfying the above formula 2, a non-aqueous electrolyte storage element in which a film containing sulfur element is sufficiently formed on the surface of the negative electrode and the remaining amount of the additive in the non-aqueous electrolyte is small is obtained, and it is speculated that the above effects are achieved.

[0024] In the manufacturing method (α) and the manufacturing method (β), the positive electrode reaching potential in the above initial charge-discharge is preferably 2.0 V (vs. Li / Li + ) or more and 4.2 V (vs. Li / Li + ) or less. By performing the initial charge-discharge at the positive electrode reaching potential within such a range, a film containing sulfur element can be sufficiently formed on the surface of the negative electrode, and the remaining amount of the additive in the non-aqueous electrolyte of the completed non-aqueous electrolyte storage element can be made into a more appropriate range.

[0025] Hereinafter, the non-aqueous electrolyte storage element and the manufacturing method of the non-aqueous electrolyte storage element according to an embodiment of the present invention will be described in order.

[0026] <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. Further, as the container, a known metal container, resin container, etc. that are usually used as the container of the secondary battery can be used.

[0027] (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.

[0028] 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 above 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 preferred in terms of the balance of potential resistance, high conductivity, and cost. In addition, as the form of the positive electrode substrate, a foil, a vapor deposition film, etc. are mentioned, and a foil is preferred in terms of cost. That is, an aluminum foil is preferred as the positive electrode substrate. Note that examples of aluminum or aluminum alloy include A1085, A3003, etc. defined in JIS-H-4000 (2014).

[0029] 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, the strength of the positive electrode substrate can be increased while increasing the energy density per volume of the secondary battery. The "average thickness" of the positive electrode substrate and the negative electrode substrate described later refers to the value obtained by dividing the punching mass when punching out a substrate of a predetermined area by the true density and the punching area of the substrate.

[0030] The intermediate layer is a coating layer on the surface of the positive electrode substrate, and contains conductive particles such as carbon particles to reduce the contact resistance between the positive electrode substrate and the positive electrode active material layer. The configuration of the intermediate layer is not particularly limited, and can be formed, for example, by a composition containing a resin binder and conductive particles.

[0031] The positive electrode active material layer is formed from a so-called positive electrode mixture containing a positive electrode active material. Further, the positive electrode mixture forming the positive electrode active material layer contains optional components such as a conductive agent, a binder, a thickener, and a filler as necessary.

[0032] As the positive electrode active material, it can be appropriately selected from known positive electrode active materials. As the positive electrode active material for a lithium-ion secondary battery, a material that can occlude and release lithium ions is usually 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-γ O2 (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. Examples of the lithium transition metal composite oxide having a spinel-type crystal structure include Li x Mn2O4, Li x Ni γ Mn 2-γExamples include O4. Examples of the polyanion compound include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, Li2CoPO4F, etc. Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, molybdenum dioxide, etc. 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.

[0033] As the positive electrode active material, a polyanion compound is preferable because, as described above, it can effectively enjoy the advantage of suppressing the increase in resistance during charge and discharge cycles. Among the polyanion compounds, a compound containing phosphate ions (PO4 3- ) (phosphate compound) is preferable, and lithium iron phosphate is more preferable. Lithium iron phosphate may be, in addition to LiFePO4, a material in which part of the atoms or polyanions of LiFePO4 are substituted with other atoms or other anion species.

[0034] The positive electrode active material is usually in the form of particles (powder). The average particle diameter of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle diameter of the positive electrode active material to be equal to or greater than the above lower limit, the production or handling of the positive electrode active material becomes easy. By setting the average particle diameter of the positive electrode active material to be equal to or less than the above upper limit, the electron conductivity of the positive electrode active material layer is improved. When a composite of the positive electrode active material and other materials is used, the average particle diameter of the composite is taken as the average particle diameter of the positive electrode active material.

[0035] To obtain powder with a predetermined particle diameter, a pulverizer, a classifier, etc. are used. Examples of the pulverization method include methods 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, or a sieve. During pulverization, wet pulverization with water or an organic solvent such as hexane coexisting can also be used. As the classification method, a sieve, an air classifier, etc. are used as needed for both dry and wet processes.

[0036] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 98% by mass or less, and still more preferably 80% by mass or more and 95% by mass or less. By setting the content of the positive electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the positive electrode active material layer.

[0037] The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such conductive agents include carbonaceous materials; metals; conductive ceramics, etc. Examples of carbonaceous materials include graphite and carbon black. Examples of the types of carbon black include furnace black, acetylene black, ketjen black, etc. Among these, from the viewpoints of conductivity and coatability, carbonaceous materials are preferred. Among them, acetylene black and ketjen black are preferred. Examples of the shape of the conductive agent include powder form, sheet form, fibrous form, etc.

[0038] 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, more preferably 2% by mass or more and 30% by mass or less, still more preferably 4% by mass or more and 20% by mass or less, and in some cases, even more preferably 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.

[0039] Examples of the binder include fluororesins (such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; polysaccharide polymers, etc.

[0040] The content of the binder in the positive electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the binder within the above range, the active material can be stably held.

[0041] Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. Further, when the thickener has a functional group that reacts with lithium, it is preferable to deactivate this functional group in advance by methylation or the like. The content of the thickener in the positive electrode active material layer is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less.

[0042] 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 such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof.

[0043] The positive electrode active material layer may contain typical non-metal elements such as B, N, P, F, Cl, Br, and I, typical metal elements such as Li, Na, Mg, Al, Si, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, and Nb as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0044] (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 can have the same configuration as the intermediate layer of the positive electrode. A film containing sulfur element is formed on the surface of the negative electrode, specifically, on the surface of the negative electrode active material layer. This film is usually formed by decomposition of additives or the like, which are compounds containing sulfur element in the non-aqueous electrolyte, during the initial charge and discharge. That is, the film contains components derived from additives in the non-aqueous electrolyte. The film may contain elements other than sulfur and may also contain components derived from sources other than additives in the non-aqueous electrolyte.

[0045] 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, or their alloys 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 a rolled copper foil and an electrolytic copper foil.

[0046] 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, it is possible to increase the strength of the negative electrode substrate while increasing the energy density per volume and per mass of the secondary battery.

[0047] The negative electrode active material layer is generally formed from a so-called negative electrode mixture containing a negative electrode active material. In addition, the negative electrode mixture forming the negative electrode active material layer contains optional components such as a conductive agent, a binder, a thickener, and a filler as required. The optional components such as a conductive agent, a binder, a thickener, and a filler can be the same as those of the positive electrode active material layer. The negative electrode active material layer may be a layer consisting essentially of only a negative electrode active material such as metallic Li.

[0048] The negative electrode active material layer may contain, as components other than the negative electrode active material, conductive agent, binder, thickener, and filler, 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, Ta, Hf, Nb, W, etc.

[0049] The negative electrode active material can be appropriately selected from known negative electrode active materials. For example, as the negative electrode active material for a lithium ion secondary battery, a material that can occlude and release lithium ions is usually used. Examples of the negative electrode active material include alkali metals such as lithium and sodium; compounds containing alkali metals such as lithium alloys, sodium alloys, and lithium composite oxides; metals or semi-metals other than alkali metals such as Si, Ge, and Sn; oxides of metals other than alkali metals or semi-metal oxides such as Si oxide, Ti oxide, and Sn oxide; Li4Ti5O 12 、LiTiO 2、 Titanium-containing oxides such as TiNb2O7; polyphosphoric acid compounds; silicon carbide; carbon materials such as graphite (graphite), non-graphitic carbon (easily graphitizable carbon or hardly graphitizable carbon), etc. As the negative electrode active material, a carbon material is preferable, and graphite is more preferable. In the negative electrode active material layer, one of these materials may be used alone, or two or more of them may be mixed and used.

[0050] "Graphite" refers to a carbon material having an average lattice plane spacing (d 002 ) of the (002) plane determined by X-ray diffraction method of 0.33 nm or more and less than 0.34 nm before charge and discharge or in a discharged state. Examples of graphite include natural graphite and artificial graphite. From the viewpoint of obtaining a material with stable physical properties, artificial graphite is preferable.

[0051] "Non-graphitic carbon" refers to the average lattice plane spacing (d 002refers to a carbon material having a d-spacing of 0.34 nm or more and 0.42 nm or less. Examples of non-graphitic carbon include non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include materials derived from resins, petroleum pitch or materials derived from petroleum pitch, petroleum coke or materials derived from petroleum coke, plant-derived materials, alcohol-derived materials, and the like.

[0052] Here, the "discharged state" of the carbon material means a state in which the open-circuit voltage is 0.7 V or more in a single electrode cell using a negative electrode containing the carbon material as the working electrode and metallic Li as the counter electrode. Since the potential of the metallic Li counter electrode in the open-circuit state is almost equal to the oxidation-reduction potential of Li, the open-circuit voltage in the above single electrode cell is almost equal to the potential of the negative electrode containing the carbon material with respect to the oxidation-reduction potential of Li. That is, the fact that the open-circuit voltage in the above single electrode cell is 0.7 V or more means that lithium ions that can be occluded and released with charge and discharge are sufficiently released from the carbon material that is the negative electrode active material.

[0053] "Non-graphitizable carbon" refers to a carbon material having a d-spacing of 0.36 nm or more and 0.42 nm or less. 002

[0054] "Graphitizable carbon" refers to a carbon material having a d-spacing of 0.34 nm or more and less than 0.36 nm. 002

[0055] When the form of the negative electrode active material is particles (powder), the average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is, for example, a carbon material, its average particle size may preferably be 1 μm or more and 100 μm or less. When the negative electrode active material is a metal, semi-metal, metal oxide, semi-metal oxide, titanium-containing oxide, polyphosphoric acid compound, or the like, its average particle size may preferably be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or greater than the above lower limit, the production or handling of the negative electrode active material becomes easy. By setting the average particle size of the negative electrode active material to be equal to or less than the above upper limit, the electron conductivity of the active material layer is improved. A pulverizer, a classifier, or the like is used to obtain powder having a predetermined particle size.

[0056] When the content of the negative electrode active material in the negative electrode active material layer is, for example, when the negative electrode active material layer is formed from a negative electrode binder, it is preferably 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the negative electrode active material layer. When the negative electrode active material is an alkali metal or a compound containing an alkali metal, the content of the negative electrode active material in the negative electrode active material layer may be 99% by mass or more, or may be 100% by mass.

[0057] As the mass of the negative electrode active material in the negative electrode active material layer, for example, it is preferably 1 g or more and 5 g or less, and more preferably 1.5 g or more and 3 g or less. When the mass of the negative electrode active material is within the above range, the thickness of the film containing sulfur element formed on the surface of the negative electrode is optimized, etc., so that the capacity retention rate in the charge-discharge cycle is further increased and the resistance increase is further suppressed.

[0058] The mass of the negative electrode active material in the negative electrode active material layer can be determined by the following procedure. Disassemble the non-aqueous electrolyte storage element in a dry room with a dew point of -40 °C or lower, and take out the negative electrode with a predetermined area. Wash the taken-out negative electrode with dimethyl carbonate (DMC) to wash away the non-aqueous electrolyte, and then perform vacuum drying at 100 °C for 5 hours. After vacuum drying, separate the negative electrode active material layer from the negative electrode, and measure the mass (A) per unit area of the negative electrode active material layer. Measure the thermogravimetric measurement (TG) of the separated negative electrode active material layer, and determine the content ratio (B) of the negative electrode active material in the negative electrode active material layer. Also, measure the facing area (C) between the positive electrode and the negative electrode in the non-aqueous electrolyte storage element. The mass of the negative electrode active material contained in the negative electrode is calculated by multiplying the mass (A) per unit area of the negative electrode active material layer, the content ratio (B) of the negative electrode active material in the negative electrode active material layer, and the facing area (C).

[0059] As the discharge capacity of the negative electrode, for example, it is preferably 0.3 Ah or more and 2.0 Ah or less, and more preferably 0.5 Ah or more and 1.0 Ah or less. When the discharge capacity of the negative electrode is within the above range, due to optimization of the thickness of the film containing sulfur element formed on the surface of the negative electrode, etc., the capacity retention rate in the charge-discharge cycle is further increased, and the increase in resistance is also further suppressed.

[0060] The discharge capacity of the negative electrode can be obtained by the following procedure. Disassemble the non-aqueous electrolyte storage element in a dry room with a dew point of -40°C or lower, take out the negative electrode with a predetermined area, and measure the area of the negative electrode active material layer of this negative electrode. Using the taken-out negative electrode, assemble a test battery with a metal lithium electrode as the counter electrode, set the test temperature to 25 ± 2°C, and perform charge and discharge under the following conditions. · Discharge (first time): After constant current discharge with a discharge current of 0.12 mA / cm 2 and a discharge cut-off voltage of 2.0 V, provide a rest period of 10 minutes. · Charge: Charge current 0.12 mA / cm 2 , charge cut-off voltage 0.02 V, and the charge cut-off condition is that the charge current is lower than 0.012 mA / cm 2 . After constant current constant voltage charging, provide a rest period of 10 minutes. · Discharge (second time): Perform constant current discharge with a discharge current of 0.12 mA / cm 2 and a discharge cut-off voltage of 2.0 V, and measure the discharge charge amount in the second discharge. Divide the discharge charge amount obtained in the second discharge by the area of the negative electrode active material layer of the negative electrode used in the test battery to obtain the discharge charge amount per unit area (a) of the negative electrode. Also, measure the facing area (b) between the positive electrode and the negative electrode in the non-aqueous electrolyte storage element. The discharge capacity of the negative electrode is calculated by multiplying the discharge charge amount per unit area (a) of the negative electrode by the facing area (b).

[0061] (Separator) The separator can be appropriately selected from known separators. As the separator, for example, a separator composed only of 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. Examples of the form 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. As the material of the base material layer of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of the shut-down function, and polyimides, aramids, etc. are preferable from the viewpoint of oxidation decomposition resistance. As the base material layer of the separator, a material obtained by compounding these resins may also be used.

[0062] The heat-resistant particles contained in the heat-resistant layer preferably have a mass reduction of 5% or less when heated from room temperature to 500 °C in the atmosphere, and more preferably have a mass reduction of 5% or less when heated from room temperature to 800 °C in the atmosphere. Examples of materials having a mass reduction 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, aluminosilicate; 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; mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, mica, or artificial products thereof, etc. As the inorganic compound, these substances may be used alone as a simple substance or a composite, or two or more kinds may be mixed and used. Among these inorganic compounds, from the viewpoint of the safety of the secondary battery, silicon oxide, aluminum oxide, or aluminosilicate is preferable.

[0063] The porosity of the separator is preferably 80% by volume or less from the viewpoint of strength, and preferably 20% by volume or more from the viewpoint of discharge performance. Here, the "porosity" is a value based on volume and means the measured value by a mercury porosimeter.

[0064] 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, polymethyl methacrylate, polyvinyl acetate, polyvinyl pyrrolidone, polyvinylidene fluoride, and the like. Using a polymer gel has the 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.

[0065] (Non-aqueous electrolyte) The non-aqueous electrolyte contains an additive. The non-aqueous electrolyte is usually a non-aqueous electrolyte solution containing a non-aqueous solvent, an electrolyte salt dissolved in this non-aqueous solvent, and the above additive.

[0066] The additive is a compound containing a sulfur element. The additive is usually an organic compound containing a sulfur element. Examples of the additive include sulfates, sulfonic acid esters, sulfones, sulfites, sulfoxides, sulfides, disulfides, and the like.

[0067] Sulfates refer to compounds containing a structure in which two carbon atoms are each bonded to an oxysulfonyloxy group (-O-S(=O)2-O-). Examples of sulfates include cyclic sulfates and chain sulfates. Specific examples of cyclic sulfates include ethylene sulfate, 1,3-propylene sulfate, 2,3-propylene sulfate, 4,5-pentene sulfate, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane), 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane, and the like. Specific examples of chain sulfates include dimethyl sulfate, diethyl sulfate, and the like.

[0068] Sulfonic acid esters refer to compounds containing a structure in which two carbon atoms are each bonded to a sulfonyloxy group (-S(=O)2O-). Examples of sulfonic acid esters include cyclic sulfonic acid esters and chain sulfonic acid esters. Specific examples of cyclic sulfonic acid esters include 1,3-propanesultone, 1,4-butanesultone, 1,3-propenesultone, 1-methyl-1,3-propenesultone, 2-methyl-1,3-propenesultone, 3-methyl-1,3-propenesultone, and the like. Specific examples of chain sulfonic acid esters include methyl methanesulfonate, ethyl methanesulfonate, and the like.

[0069] Sulfones refer to compounds containing a structure in which two carbon atoms are each bonded to a sulfonyl group (-S(=O)2-). Examples of sulfones include cyclic sulfones and chain sulfones. Specific examples of cyclic sulfones include sulfolane, 3-methylsulfolane, 3-sulfolene, 1,1-dioxothiophene, 3-methyl-2,5-dihydrothiophene-1,1-dioxide, methyl 3-sulfolene-3-carboxylate, and the like. Specific examples of chain sulfones include dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, divinyl sulfone, and the like.

[0070] Sulfites refer to compounds containing a structure in which two carbon atoms are each bonded to an oxysulfinyl oxy group (-O-S(=O)-O-). Examples of sulfites include cyclic sulfites and chain sulfites. Specific examples of cyclic sulfites include ethylene sulfite, 1,2-propylene glycol sulfite, trimethylene sulfite, 1,3-butylene glycol sulfite, and the like. Specific examples of chain sulfites include dimethyl sulfite, and the like.

[0071] Sulfoxides refer to compounds containing a structure in which two carbon atoms are each bonded to a sulfinyl group (-S(=O)-). Examples of sulfoxides include cyclic sulfoxides and chain sulfoxides. Specific examples of cyclic sulfoxides include tetramethylene sulfoxide and the like. Specific examples of chain sulfoxides include dimethyl sulfoxide, diethyl sulfoxide and the like.

[0072] Sulfides refer to compounds containing a structure in which two carbon atoms are each bonded to a divalent sulfur (-S-). Examples of sulfides include cyclic sulfides and chain sulfides. Specific examples of cyclic sulfides include tetrahydrothiophene, thiophene, thian, 1,3-dithiane, 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydride, 3,4-thiophenedicarboxylic anhydride and the like. Specific examples of chain sulfides include diallyl sulfide, diphenyl sulfide, thioanisole and the like.

[0073] Disulfides refer to compounds containing a structure in which two carbon atoms are each bonded to a disulfide group (-S-S-). Examples of disulfides include cyclic disulfides and chain disulfides. Specific examples of disulfides include diphenyl disulfide, dipyridinium disulfide, diallyl disulfide and the like.

[0074] As the additive, a compound containing a sulfonyl group (-S(=O)2-) structure is preferred. Such compounds include the sulfates, sulfonic acid esters, sulfones and the like described above, and sulfates are preferred.

[0075] Among sulfates, ethylene sulfate, 1,3-propylene sulfate, 2,3-propylene sulfate, 4,5-pentene sulfate, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane), and 4-methylsulfonyloxymethyl-2,2-dioxo-1,3,2-dioxathiolane are preferred, and ethylene sulfate, 1,3-propylene sulfate, 2,3-propylene sulfate, 4,5-pentene sulfate, and 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane) are more preferred. These compounds have approximately the same sulfur atom content per molecular weight or sulfonyl group structure content per molecular weight. Therefore, especially when any of these compounds is used, it can be expected that the same effects will be achieved if the concentrations in the non-aqueous electrolyte are the same.

[0076] As the additive, a compound having a cyclic structure is preferred, a compound containing a sulfur atom in the cyclic structure is more preferred, and a compound containing a sulfonyl group structure in the cyclic structure is even more preferred. The additive preferably contains sulfur and oxygen elements, and more preferably is composed of sulfur, oxygen, carbon, and hydrogen elements. The additive preferably has two sulfonyl groups or two oxysulfonyloxy groups in one molecule. Also, the additive is preferably a molecular compound rather than an ionic compound. Such a compound can increase the capacity retention rate in the charge-discharge cycle of the secondary battery and suppress the increase in resistance more effectively because it decomposes efficiently during the initial charge-discharge and has relatively little adverse effect on the positive electrode, etc. even when remaining in the non-aqueous electrolyte.

[0077] The upper limit of the concentration of the additive in the non-aqueous electrolyte is 0.2% by mass, preferably 0.17% by mass, more preferably 0.14% by mass, still more preferably 0.12% by mass, and in some cases even more preferably 0.08% by mass or less than 0.05% by mass. By setting the concentration of the additive to be equal to or less than the upper limit, an increase in resistance during charge and discharge cycles of the secondary battery is suppressed. On the other hand, the lower limit of the concentration of the additive may be, for example, 0.001% by mass, but preferably 0.01% by mass, and in some cases more preferably 0.05% by mass. By setting the concentration of the additive to be equal to or higher than the lower limit, the capacity retention rate during charge and discharge cycles of the secondary battery increases. The concentration of the additive may be within the range of equal to or higher than any of the above-mentioned lower limits and equal to or lower than any of the above-mentioned upper limits.

[0078] 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, ethers, amides, nitriles, etc. As the non-aqueous solvent, those in which a part of the hydrogen atoms are substituted with halogens may be used.

[0079] Examples of the cyclic carbonate include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylvinylene carbonate, 1,2-diphenylvinylene carbonate, etc. Among these, EC is preferred.

[0080] Examples of the chain carbonate include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, trifluoroethyl methyl carbonate (TFEMC), bis(trifluoroethyl) carbonate, etc. Among these, DMC and EMC are preferred.

[0081] As the non-aqueous solvent, it is preferable to use a cyclic carbonate or a linear carbonate, and it is more preferable to use a cyclic carbonate and a linear carbonate in combination. By using the 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 the linear carbonate, the viscosity of the non-aqueous electrolyte can be kept low. When using a cyclic carbonate and a linear carbonate in combination, the volume ratio of the cyclic carbonate to the linear carbonate (cyclic carbonate: linear carbonate) is preferably in the range of, for example, 5:95 to 50:50, and more preferably in the range of 10:90 to 30:70.

[0082] As the electrolyte salt, it can be appropriately selected from known electrolyte salts. Examples of the electrolyte salt include lithium salts, sodium salts, potassium salts, magnesium salts, onium salts, etc. Among these, lithium salts are preferable.

[0083] Examples of the lithium salt include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiPO2F2, LiN(SO2F)2, and lithium salts having a halogenated hydrocarbon group such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, LiC(SO2C2F5)3, etc. Among these, inorganic lithium salts are preferable, and LiPF6 is more preferable.

[0084] The content of the electrolyte salt 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.

[0085] The non-aqueous electrolyte may contain other additives other than the additive which is a compound containing the sulfur element described above. Examples of the other additives include aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, etc.; partial halides of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene, etc.; halogenated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoroanisole, etc.; succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; perfluorooctane, tris(trimethylsilyl) phosphate, tetrakis(trimethylsilyl) titanate, etc. These additives may be used alone or in combination of two or more.

[0086] The content of the other additives 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, even more preferably 0.3% by mass or more and 3% by mass or less, and may also be 2% by mass or less or 1% by mass or less. By setting the content of the other additives within the above range, the capacity retention performance or charge-discharge cycle performance after high-temperature storage of the secondary battery can be improved, or the safety can be further improved.

[0087] As the non-aqueous electrolyte, a non-aqueous electrolyte solution and a solid electrolyte may be used in combination. As the solid electrolyte, any material having lithium ion conductivity and being solid at 60°C or lower can be selected. Examples of the solid electrolyte include sulfide solid electrolytes, oxide solid electrolytes, oxynitride solid electrolytes, polymer solid electrolytes, etc.

[0088] The shape of the non-aqueous electrolyte storage element of the present embodiment is not particularly limited, and examples thereof include a cylindrical battery, a laminated film battery, a prismatic battery, a flat battery, a coin battery, a button battery, and the like.

[0089] FIG. 1 shows a non-aqueous electrolyte storage element 1 as an example of a prismatic battery. Note that this figure is a perspective view of the inside of the case. An electrode body 2 having a positive electrode and a negative electrode wound with a separator interposed therebetween is housed in a prismatic container 3. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 41. The negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 51.

[0090] <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 vehicles (HEVs), plug-in hybrid 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.

[0091] 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.

[0092] <Manufacturing method of non-aqueous electrolyte storage element (α)> The manufacturing method of a non-aqueous electrolyte storage element according to an embodiment of the present invention includes assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element. The additive is a compound containing a sulfur element, and it is a manufacturing method (α) of a non-aqueous electrolyte storage element that satisfies the following formula 1. 0.004 ≦ m S / m N ≦ 0.016 ··· 1 In formula 1, m S is the mass (g) of the additive contained in the non-aqueous electrolyte. m N is the mass (g) of the negative electrode active material contained in the negative electrode.

[0093] Specifically, assembling the uncharged and discharged storage element may include preparing a positive electrode containing a positive electrode active material, preparing a negative electrode containing a negative electrode active material, preparing a non-aqueous electrolyte containing an additive, forming an electrode body in which the positive electrode and the negative electrode are alternately stacked by laminating or winding through a separator, 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 an uncharged and discharged storage element.

[0094] The positive electrode provided for assembling the uncharged and discharged storage element may be the same as the positive electrode provided in the non-aqueous electrolyte storage element according to an embodiment of the present invention described above. The negative electrode provided for assembling the uncharged and discharged storage element may be the same as the negative electrode provided in the non-aqueous electrolyte storage element according to an embodiment of the present invention described above, except that a film containing a sulfur element is usually not formed on the surface.

[0095] The non-aqueous electrolyte provided for assembling the uncharged and discharged storage element may be the same as the non-aqueous electrolyte provided in the non-aqueous electrolyte storage element according to an embodiment of the present invention described above, except that the concentration of the additive is not limited. However, in the manufacturing method (α), the above formula 1 is satisfied in the relationship between the non-aqueous electrolyte used and the negative electrode. m in formula 1 S(The mass of the additive contained in the non-aqueous electrolyte) is the product of the injection amount (mass) of the non-aqueous electrolyte and the concentration of the additive in the non-aqueous electrolyte to be injected. The concentration of the additive in the non-aqueous electrolyte to be injected may be, for example, 0.1% by mass or more and 2% by mass or less, and may be 0.2% by mass or more and 1% by mass or less.

[0096] m S / m N The lower limit of is preferably 0.006 in some cases. m S / m N The upper limit of is preferably 0.015 or 0.010 in some cases.

[0097] For the obtained uncharged and discharged storage element, as the initial charge and discharge, charge and discharge are performed one or more times. At this time, a part of the additive in the non-aqueous electrolyte is decomposed, and a film containing sulfur element is formed on the surface of the negative electrode. As the positive electrode reaching potential in the above initial charge and discharge, 2.0 V (vs. Li / Li + ) or more and 4.2 V (vs. Li / Li + ) or less is preferable, and 3.0 V (vs. Li / Li + ) or more and 3.7 V (vs. Li / Li + ) or less is more preferable.

[0098] In the manufacturing method (α), by going through such steps, a film containing sulfur element is formed on the surface of the negative electrode, and a non-aqueous electrolyte storage element with a small remaining amount of the additive in the non-aqueous electrolyte is obtained. Therefore, the obtained non-aqueous electrolyte storage element has a high capacity retention rate in the charge and discharge cycle and suppressed resistance increase. Specific examples and preferred examples of the non-aqueous electrolyte storage element obtained by the manufacturing method (α) can be the examples of the non-aqueous electrolyte storage element according to one embodiment of the present invention described above.

[0099] <Manufacturing method (β) of non-aqueous electrolyte storage element> A method for manufacturing a nonaqueous electrolyte storage element according to another embodiment of the present invention is a method (β) for manufacturing a nonaqueous electrolyte storage element, comprising assembling an uncharged / discharged storage element using a negative electrode containing a negative electrode active material and a nonaqueous electrolyte containing an additive, and initially charging / discharging the uncharged / discharged storage element, wherein the additive is a compound containing elemental sulfur and satisfies the following formula 2: 0.010≦m S / c N ≦0.048 2 In formula 2, m S is the mass (g) of the additive contained in the non-aqueous electrolyte. N is the discharge capacity (Ah) of the negative electrode.

[0100] The production method (β) does not necessarily satisfy the above formula 1, and is similar to the above production method (α) except that it satisfies the above formula 2. Therefore, specific examples and suitable examples of the production method (β) can refer to the examples of the production method (α) described above. N The (discharge capacity of the negative electrode) is adjusted by the amount, type, etc. of the negative electrode active material.

[0101] m S / c N The lower limit of m may be preferably 0.020. S / c N The upper limit of is preferably 0.047, and more preferably 0.045 or 0.035 in some cases.

[0102] In the production method (β), by going through these steps, a coating containing elemental sulfur is formed on the surface of the negative electrode, and a nonaqueous electrolyte storage element is obtained in which the amount of residual additive in the nonaqueous electrolyte is small. Therefore, the obtained nonaqueous electrolyte storage element has a high capacity retention rate during charge-discharge cycles and a suppressed increase in resistance. Specific and preferred examples of the nonaqueous electrolyte storage element obtained by the production method (β) include the example of the nonaqueous electrolyte storage element according to one embodiment of the present invention described above.

[0103] <Other embodiments> The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the gist of the present invention. For example, the configuration of one embodiment may be added to the configuration of another embodiment, and a part of the configuration of one embodiment may be replaced with the configuration of another embodiment or well-known technology. Further, a part of the configuration of one embodiment may be deleted. In addition, well-known technology may be added to the configuration of one embodiment.

[0104] In the above embodiment, the case where the non-aqueous electrolyte storage element is used as a non-aqueous electrolyte secondary battery (for example, a lithium-ion secondary 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

[0105] Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to the following examples.

[0106] [Example 1] (Fabrication of positive electrode) A positive electrode mixture paste containing lithium iron phosphate as a positive electrode active material, polyvinylidene fluoride (PVDF) as a binder, and acetylene black as a conductive agent, with N-methylpyrrolidone (NMP) as a dispersion medium, was prepared. The ratio of the positive electrode active material, binder, and conductive agent was 90:5:5 by mass ratio. The positive electrode mixture paste was coated on the surface of an aluminum foil as a positive electrode substrate, dried, and then the coated layer was compressed to a predetermined thickness to form a positive electrode active material layer, thereby obtaining a positive electrode.

[0107] (Fabrication of negative electrode) A negative electrode mixture paste was prepared containing graphite as a negative electrode active material, styrene butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener, with water as a dispersion medium. The ratio of the negative electrode active material, binder, and thickener was 97:1:2 by mass ratio. The negative electrode mixture paste was coated on the surface of a copper foil as a negative electrode substrate, dried, and then the coated layer was compressed to a predetermined thickness to form a negative electrode active material layer, thereby obtaining a negative electrode.

[0108] (Preparation of non-aqueous electrolyte) Lithium hexafluorophosphate (LiPF6) as an electrolyte salt was mixed in a non-aqueous solvent formed by mixing ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a volume ratio of 20:35:45 to a content of 0.9 mol / dm 3 . To this mixed solution, 4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane) (additive A) as an additive was added at a concentration of 1.0% by mass, vinylene carbonate was added at a concentration of 0.3% by mass, and lithium difluorophosphate was added at a concentration of 1.0% by mass to prepare a non-aqueous electrolyte.

[0109] (Assembly of non-aqueous electrolyte storage element) The above positive electrode and negative electrode, and a polyethylene separator were laminated and wound to produce a wound electrode body. The wound electrode body was housed in a container. Then, the non-aqueous electrolyte was injected into the container to obtain an uncharged and discharged storage element. The mass (injection amount) of the injected non-aqueous electrolyte was 3.34 g.

[0110] (Initial charge and discharge) For the obtained uncharged and discharged storage element, constant current constant voltage (CCCV) charging was performed in a thermostat at 25°C under the conditions of a charging current of 1C and a charging end voltage of 3.6V until the total charging time reached 3 hours. Then, constant current (CC) discharge was performed under the conditions of a discharge current of 1C and a discharge end voltage of 2.0V. Through the above initial charge and discharge, the completed non-aqueous electrolyte storage element of Example 1 was obtained. The amount of electricity during discharge in this initial charge and discharge was defined as the initial discharge capacity.

[0111] The completed non-aqueous electrolyte device of Example 1 obtained was disassembled, and the concentration of additive A (4,4'-bis(2,2-dioxo-1,3,2-dioxathiolane)) in the non-aqueous electrolyte was measured, and it was 0.12 mass%. Further, the opposing area between the positive electrode and the negative electrode in the non-aqueous electrolyte storage device of Example 1 was 436.1 cm 2 , the mass of the negative electrode active material was 2.242 g, and the discharge capacity of the negative electrode was 0.772 Ah.

[0112] [Examples 2 to 4, Comparative Examples 1 to 3] Except that the concentration of additive A (4,4'-bis(,2-dioxo-1,3,2-dioxathiolane)) in the non-aqueous electrolyte used for production and the mass (injection amount) of the non-aqueous electrolyte injected into the container were as described in Table 1, each non-aqueous electrolyte storage device of Examples 2 to 4 and Comparative Examples 1 to 3 was produced in the same manner as Example 1. The completed non-aqueous electrolyte storage devices of Examples 2 to 4 and Comparative Examples 1 to 3 obtained were disassembled, and the concentration of additive A in the non-aqueous electrolyte was measured. The measurement results are shown in Table 1.

[0113] Further, Table 1 also shows the mass (m S ) of additive A in each non-aqueous electrolyte used for production in each example and comparative example, the ratio (m S / m N ) of the mass of additive A in the non-aqueous electrolyte to the mass of the negative electrode active material contained in the negative electrode, and the ratio (m S / c N ) of the mass of additive A in the non-aqueous electrolyte to the discharge capacity of the negative electrode.

[0114] [Evaluation] (Charge and Discharge Cycle Test) For each of the obtained non-aqueous electrolyte storage devices, a charge and discharge cycle test was conducted as follows. At 60 °C, constant current constant voltage charging was performed with a charging current of 1.0 C and a charging termination voltage of 3.6 V. The charging termination condition was the time when the current value decayed to 0.1 C. Thereafter, constant current discharge was performed with a discharge current of 1.0 C and a discharge termination voltage of 2.0 V. A rest period of 10 minutes was provided after charging and after discharge, respectively. This charge and discharge was performed for 100 cycles.

[0115] (DCR increase rate) Before and after the charge-discharge cycle test, for each non-aqueous electrolyte storage element, the direct current resistance (DCR) was measured as follows. At 25°C, constant current charging was performed with a charging current of 1C. After setting the state of charge (SOC) to 50%, discharging was performed at 25°C with a discharging current of 0.2C, 0.5C, or 1.0C for 30 seconds. The relationship between the current at each discharging current and the voltage at the 10th second after the start of discharging was plotted, and the DCR was obtained from the slope of the straight line obtained from the three-point plot. For each non-aqueous electrolyte storage element, the increase rate of the DCR after the charge-discharge cycle test with respect to the initial DCR (before the charge-discharge cycle test) was determined. The measurement results are shown in Table 1.

[0116] (Capacity retention rate) After the charge-discharge cycle test, for each non-aqueous electrolyte storage element, charging and discharging were performed under the same conditions as the initial charging and discharging, and the discharge capacity after the charge-discharge cycle test was measured. Then, the discharge capacity after the charge-discharge cycle test with respect to the initial discharge capacity was defined as the capacity retention rate. The capacity retention rates of the non-aqueous electrolyte storage elements are shown in Table 1 as relative values with the capacity retention rate of the non-aqueous electrolyte storage element of Comparative Example 1 as the reference (100%).

[0117]

Table 1

[0118] As shown in Table 1, in the non-aqueous electrolyte storage elements of Comparative Examples 1 and 2 where the concentration of additive A in the non-aqueous electrolyte in the completed non-aqueous electrolyte storage element is high, the DCR increases significantly after the charge-discharge cycle test. On the other hand, in the non-aqueous electrolyte storage element of Comparative Example 3 where additive A is not added to the non-aqueous electrolyte, the capacity retention rate in the charge-discharge cycle is low. In contrast, in the non-aqueous electrolyte storage elements of Examples 1 to 4 where the concentration of additive A in the non-aqueous electrolyte in the completed non-aqueous electrolyte storage element is in the range of 0.2 mass% or less, it can be seen that the capacity retention rate in the charge-discharge cycle is high and the increase in DCR is suppressed.

[0119] Also, from the results of the examples and comparative examples, it can be seen that the concentration of additive A in the non-aqueous electrolyte in the completed non-aqueous electrolyte storage element can be adjusted by setting the ratio (m S / m N ) of the mass of additive A in the non-aqueous electrolyte used in the production to the mass of the negative electrode active material contained in the negative electrode, and the ratio (m S / c N ) of the mass of additive A in the non-aqueous electrolyte used in the production to the discharge capacity of the negative electrode within a predetermined range.

Industrial Applicability

[0120] 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

[0121] 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 polyanion compound, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte containing an additive are provided, a film containing sulfur element is formed on the surface of the negative electrode, the additive is a cyclic sulfate, and the concentration of the additive in the non-aqueous electrolyte is 0.2% by mass or less, a non-aqueous electrolyte storage element.

2. a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte containing an additive are provided, a film containing sulfur element is formed on the surface of the negative electrode, the additive is a cyclic sulfate, and the concentration of the additive in the non-aqueous electrolyte is 0.05% by mass or more and 0.2% by mass or less, a non-aqueous electrolyte storage element.

3. assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element are provided, the negative electrode active material is a carbon material, the additive is a cyclic sulfate, satisfies the following formula 1, a method for manufacturing a non-aqueous electrolyte storage element, wherein the positive electrode reaching potential at the charge termination voltage of the initial charge and discharge is 3.0 V (vs. Li / Li+) or more and 4.2 V (vs. Li / Li+) or less. 0.004 ≤ m Ｓ / m Ｎ ≤ 0.016 ··· 1 In Formula 1, m Ｓ is the mass (g) of the additive contained in the non-aqueous electrolyte in the uncharged and discharged storage element. m Ｎ is the mass (g) of the negative electrode active material contained in the negative electrode.

4. assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element are provided, the negative electrode active material is a carbon material, the additive is a cyclic sulfate, satisfies the following formula 1, a method for manufacturing a non-aqueous electrolyte storage element, wherein the initial charge and discharge is a charge and discharge for capacity confirmation. 0.004 ≤ m Ｓ / m Ｎ ≤ 0.016 ··· 1 In Formula 1, m Ｓ is the mass (g) of the additive contained in the non-aqueous electrolyte in the uncharged / discharged storage element. m Ｎ is the mass (g) of the negative electrode active material contained in the negative electrode.

5. assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element are provided, the additive is a cyclic sulfate, satisfies the following formula 2, a method for manufacturing a non-aqueous electrolyte storage element, wherein the positive electrode reaching potential at the charge termination voltage of the initial charge and discharge is 3.0 V (vs. Li / Li+) or more and 4.2 V (vs. Li / Li+) or less. 0.010 ≤ m Ｓ / c Ｎ ≤ 0.048 ··· 2 In Formula 2, m Ｓ is the mass (g) of the additive contained in the non-aqueous electrolyte in the non-charged / discharged storage element. c Ｎ is the discharge capacity (Ah) of the negative electrode.

6. assembling an uncharged and discharged storage element using a negative electrode containing a negative electrode active material and a non-aqueous electrolyte containing an additive, and performing initial charge and discharge on the uncharged and discharged storage element are provided, the additive is a cyclic sulfate, satisfies the following formula 2, a method for manufacturing a non-aqueous electrolyte storage element, wherein the initial charge and discharge is a charge and discharge for capacity confirmation. 0.010 ≤ m Ｓ / c Ｎ ≤ 0.048 ··· 2 In Formula 2, m Ｓ is the mass (g) of the additive contained in the non-aqueous electrolyte in the uncharged and discharged storage element. c Ｎ is the discharge capacity (Ah) of the negative electrode.

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