Energy storage components

Abstract

One aspect of the present invention relates to an energy storage element comprising a wound electrode body, a housing housing the electrode body, and a spacer disposed inside the housing between the electrode body and the inner surface of the housing; the wound electrode body has a negative electrode containing a negative electrode active material, a positive electrode, and a spacer disposed between the positive electrode and the negative electrode; the spacer has a wet membrane, the negative electrode active material is a carbonaceous material or lithium titanate, and the spacer is harder than the spacer.

Description

Technical Field

[0001] This invention relates to energy storage components. Background Technology

[0002] Patent Document 1 describes an energy storage device characterized by having a housing and an electrode assembly; the electrode assembly is housed in the housing and has a layered structure insulated between a first electrode and a second electrode of a different polarity from the first electrode by an insulating member; the insulating member includes a first insulating member and a second insulating member having a ceramic layer, clamping the first electrode or the second electrode, and the second insulating member and the first insulating member are arranged sequentially.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-220079 Summary of the Invention

[0006] The purpose of this invention is to provide an energy storage element with a smaller space in the winding center portion of its electrode body and the ability to suppress the increase in air permeability of the separator with a wet membrane.

[0007] One aspect of the present invention relates to an energy storage element comprising a wound electrode body, a housing housing the electrode body, and a spacer disposed inside the housing between the electrode body and the inner surface of the housing;

[0008] The wound electrode body has a negative electrode containing a negative electrode active material, a positive electrode, and an insulating member disposed between the positive electrode and the negative electrode;

[0009] The aforementioned separator has a wet membrane.

[0010] The aforementioned negative electrode active material is a carbonaceous material or lithium titanate.

[0011] The aforementioned isolation material is harder than the aforementioned isolation component.

[0012] One aspect of the present invention relates to a storage element in which the space of the winding center portion of the electrode body is small, and the increase in the air permeability of the separator having a wet membrane can be suppressed. Attached Figure Description

[0013] Figure 1 This is a perspective view of the energy storage element involved in this embodiment.

[0014] Figure 2 for Figure 1 A schematic cross-sectional view of the location of line II-II.

[0015] Figure 3 for Figure 1 A schematic cross-sectional view of the position of line III-III.

[0016] Figure 4 This is a perspective view of the wound electrode body of the energy storage element according to this embodiment.

[0017] Figure 5 This is a schematic diagram of an energy storage device having multiple energy storage elements according to this embodiment.

[0018] Explanation of reference numerals in the attached figures

[0019] 1: Energy storage components (non-aqueous electrolyte secondary batteries)

[0020] 2: Electrode body; 21: Flat portion; 22: Folded portion;

[0021] y: boundary portion; z: space of the winding center portion of the electrode body.

[0022] 3: Shell, 31: Shell body, 32: Cover,

[0023] 4: Positive extreme, 5: Negative extreme

[0024] 40: Positive electrode

[0025] 41: Positive electrode substrate; 42: Positive electrode active material layer;

[0026] 50: Negative electrode

[0027] 51: Negative electrode substrate; 52: Negative electrode active material layer;

[0028] 60: Isolating component; 70: Isolating material; 80: Insulating sheet.

[0029] 10: Energy storage unit; 100: Energy storage device. Detailed Implementation

[0030] First, a general overview of the energy storage components disclosed in this specification will be given.

[0031] One aspect of the present invention relates to an energy storage element 1 comprising a wound electrode body 2, a housing 3 housing the electrode body 2, and a spacer 70 disposed inside the housing 3 between the electrode body 2 and the inner surface of the housing.

[0032] The wound electrode body 2 has a negative electrode containing a negative electrode active material, a positive electrode, and a separator 60 disposed between the positive electrode and the negative electrode;

[0033] The aforementioned separator 60 has a wet membrane.

[0034] The aforementioned negative electrode active material is a carbonaceous material or lithium titanate.

[0035] The aforementioned isolation material 70 is harder than the aforementioned isolation component 60.

[0036] The aforementioned energy storage element 1 includes a wound electrode body 2. In the wound electrode body 2, a space z is formed at the center of the winding. Generally, the innermost portion of such an electrode body 2 can deform in a way that protrudes towards the space z at the center of the winding; therefore, the distance between the positive and negative electrodes in the deformed inner portion may sometimes widen. Therefore, in the wound electrode body 2 housed in the casing 3, it is desirable to minimize the space z at the center of the winding.

[0037] Therefore, as in this embodiment, by providing a relatively rigid separator 70 (gap filling member) between the housing 3 and the electrode body 2, the space z of the winding center portion is reduced to the portion where the separator 70 is provided. Therefore, in the energy storage element 1 of this embodiment, the space z of the winding center portion of the electrode body 2 is smaller.

[0038] However, the electrode 2 housed within the housing 3 expands during charging and discharging. Therefore, the reaction force during expansion can squeeze the electrode 2 from the outside by the inner surface of the housing 3. Consequently, the pores of the separator 60 are damaged, leading to an increase in the air permeability of the separator 60. In particular, the separator 60 has a wet membrane, which contains many tortuous pores; therefore, the increased air permeability caused by the damage to the pores easily becomes a problem.

[0039] In this embodiment, by using a carbonaceous material or lithium titanate with a low expansion rate as the negative electrode active material, the expansion of the electrode body 2 can be suppressed. This suppression of the expansion of the electrode body 2 also prevents the inner surface of the housing from compressing the electrode body 2 due to the reaction force of the expansion force. Therefore, the destruction of the pores of the wet membrane can be prevented, and the increase in the permeability of the separator can be suppressed.

[0040] Thus, in the energy storage element 1 of this embodiment, the space z of the winding center portion of the electrode body 2 is small, and the increase in the air permeability of the separator with a wet membrane can be suppressed.

[0041] Here, the negative electrode active material can be non-graphitic carbon, which is a carbonaceous material.

[0042] Therefore, the expansion of the negative electrode active material can be more effectively suppressed, and for the same reasons as above, the increase in the air permeability of the separator with a wet membrane can be further suppressed.

[0043] Furthermore, the housing 3 can be held in a fixed-size manner. In this case, it becomes easy for the permeability of the insulating element to increase.

[0044] For example, when the electrode body, which occupies most of the internal volume of the housing 3, is housed in the housing 3, if the housing is held in a fixed-size manner, a large pressure (reaction force) can be applied to the electrode body 2 through the inner surface of the housing 3. This pressure (reaction force) can easily damage the pores of the wet membrane, and the air permeability of the separator 60 can easily increase.

[0045] Thus, in the energy storage element 1 where the permeability of the insulating member 60 easily increases because the housing 3 is held in a fixed size manner, by having the above-described configuration (the negative electrode active material is a carbonaceous material or lithium titanate), it is particularly possible to suppress the increase in the permeability of the insulating member 60.

[0046] In addition, the separator 70 and the separator 60 are respectively made with a surface area of ​​3680 mm². 2 When the pressure head is compressed with a load of 7kN, the displacement of the isolation member 60 can be more than 0.1mm / mm greater than the displacement of the isolation object 70.

[0047] As the separator 70, by using a separator 70 whose displacement is less than or equal to the displacement of the separator 60 as described above, deformation of the separator 70 due to compressive force is less likely to occur. Correspondingly, the electrode body 2 can withstand the reaction force from the separator 70 when it expands further. This force makes it easier for the pores of the wet membrane to be damaged, and for the permeability of the separator 60 to increase.

[0048] Thus, in the energy storage element 1 where the permeability of the separator 60 easily increases, by having the above-described configuration (the negative electrode active material is a carbonaceous material or lithium titanate), it is particularly possible to suppress the increase in the permeability of the separator 60.

[0049] The aforementioned energy storage element 1 may have an insulating sheet 80 that covers the electrode body 2 and insulates the electrode body 2 from the housing 3. Furthermore, the housing 3 is made of metal, and the separator 70 may be disposed between the electrode body 2 and the insulating sheet 80.

[0050] By making the housing 3 metallic, its strength is increased, thus suppressing deformation even when the electrode body 2 expands. Therefore, it is easier to compress the electrode body 2 through the inner surface of the housing, further increasing the permeability of the insulating member 60.

[0051] Even in the above-described energy storage element with such a configuration, as described above, by having a negative electrode active material that is carbonaceous or lithium titanate and a separator that is harder than the separator, the increase in the permeability of the separator 60, which is prone to increase in permeability, can be effectively suppressed.

[0052] The configuration of the non-aqueous electrolyte energy storage element 1 according to one embodiment of the present invention, the configuration of the non-aqueous electrolyte energy storage device, the manufacturing method of the non-aqueous electrolyte energy storage element 1, and other embodiments will be described in detail. It should be noted that the names of the constituent components (structural elements) used in each embodiment may differ from the names of the constituent components (structural elements) used in the prior art.

[0053] <Composition of Non-Aqueous Electrolyte Storage Components>

[0054] The non-aqueous electrolyte energy storage element 1 (hereinafter also simply referred to as "energy storage element") according to the embodiments of the present invention includes an electrode body 2, a non-aqueous electrolyte, and a housing 3 that houses the electrode body 2 and the non-aqueous electrolyte. The electrode body 2 has a positive electrode 40, a negative electrode 50, and a separator 60. The electrode body 2 is a wound type formed by stacking the positive electrode 40 and the negative electrode 50 through the separator 60 (described in detail below). The non-aqueous electrolyte exists in a state including the positive electrode 40, the negative electrode 50, and the separator 60. Hereinafter, as an example of a non-aqueous electrolyte energy storage element, a non-aqueous electrolyte secondary battery (particularly a lithium-ion secondary battery, hereinafter also simply referred to as "secondary battery") will be described, but this is not intended to limit the scope of the present invention.

[0055] The energy storage element 1 in this embodiment is as follows: Figures 1 to 4 As shown, the device includes a wound electrode body 2 and a housing 3 that houses the electrode body 2. Furthermore, the energy storage element 1 has two external terminals (positive terminal 4 and negative terminal 5) that are either partially exposed and mounted on or formed from at least a portion of the housing 3. The electrode body 2 is connected to each of the external terminals 4 and 5 within the housing 3 via current collectors or the like.

[0056] like Figure 4 As shown, the electrode body 2 is formed by overlapping and further winding an elongated sheet-shaped positive electrode 40, an elongated sheet-shaped negative electrode 50, and two sheet-shaped insulating members 60, 60. The two insulating members 60, 60 are respectively arranged to electrically insulate the positive electrode 40 and the negative electrode 50. In this embodiment, the electrode body 2 is a flat wound body. The electrode body 2 is arranged inside the housing 3 such that the winding axis direction of the electrode body 2 is perpendicular to the opening direction of the housing body 31. Figure 2 As shown, only a small space z is formed in the center of the winding of the electrode body 2.

[0057] (positive electrode)

[0058] The positive electrode 40 has a positive electrode substrate 41 and a positive electrode active material layer 42 disposed on the positive electrode substrate 41 directly or via an intermediate layer (not shown). In this embodiment, the positive electrode active material layer 42 is overlapped on both sides of the positive electrode substrate 41. The positive electrode active material layer 42 generates a charge-discharge reaction between the negative electrode active material layer 52.

[0059] The positive electrode substrate 41 is conductive. Whether it is "conductive" is determined by a volume resistivity of 10⁻⁶, as measured according to JIS-H-0505 (1975). 7 The threshold value is Ω·cm. The material for the positive electrode substrate 41 can be metals such as aluminum, titanium, tantalum, and stainless steel, or their alloys. Among these, aluminum or aluminum alloys are preferred from the viewpoints of high potential resistance, high conductivity, and cost. Examples of positive electrode substrates 41 include foil and vapor-deposited films; from a cost perspective, foil is preferred. Therefore, aluminum foil or aluminum alloy foil is preferred as the positive electrode substrate 41. Examples of aluminum or aluminum alloys include A1085 and A3003 as specified in JIS-H-4000 (2014).

[0060] The average thickness of the positive electrode substrate 41 is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, even more preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. By making the average thickness of the positive electrode substrate 41 within the above range, the strength of the positive electrode substrate 41 can be improved, thereby increasing the energy density per unit volume of the secondary battery.

[0061] The intermediate layer is disposed between the positive electrode substrate 41 and the positive electrode active material layer 42. The intermediate layer contains conductive particles such as carbon particles, thereby reducing the contact resistance between the positive electrode substrate 41 and the positive electrode active material layer 42. The composition of the intermediate layer is not particularly limited; for example, it may contain a resin binder and conductive particles.

[0062] The positive electrode active material layer 42 contains positive electrode active material. The positive electrode active material layer 42 may also contain, as needed, any components such as conductive agents, binders, thickeners, and fillers.

[0063] As the positive electrode active material, it can be appropriately selected from known positive electrode active materials. For positive electrode active materials used in lithium-ion secondary batteries, materials capable of absorbing and releasing lithium ions are typically used. Examples of positive electrode active materials include lithium transition metal composite oxides with an α-NaFeO2-type crystal structure, lithium transition metal composite oxides with a spinel-type crystal structure, polyanionic compounds, chalcogenide compounds, and sulfur. For example, Li[Li] can be used as a lithium transition metal composite oxide with an α-NaFeO2-type crystal structure. 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. As a lithium transition metal composite oxide with a spinel-type crystal structure, Li can be cited as an example. x Mn2O4, Li x Ni γ Mn (2-γ) Examples of polyanionic compounds include O4, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogenide compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or a portion of the polyanions in these materials can be replaced by atoms or anions formed from other elements. The surfaces of these materials can also be coated with other materials. One of these materials can be used alone, or two or more can be used in combination in the positive electrode active material layer 42.

[0064] The positive electrode active material is typically in the form of particles (powder). The average particle size of the positive electrode active material is preferably set to, for example, 0.1 μm to 20 μm. By setting the average particle size of the positive electrode active material to the lower limit or above, the manufacture or processing of the positive electrode active material becomes easier. By setting the average particle size of the positive electrode active material to the upper limit or below, the electronic conductivity of the positive electrode active material layer 42 is improved. It should be noted that when using a composite of the positive electrode active material and other materials, the average particle size of the composite is used as the average particle size of the positive electrode active material. "Average particle size" refers to the value calculated according to JIS-Z-8819-2 (2001) as 50% of the volumetric cumulative distribution, obtained by diluting particles with a solvent to obtain a diluted solution, measuring the particle size distribution of the diluted solution using laser diffraction and scattering, and diffraction.

[0065] To obtain powder with a specified particle size, pulverizers, classifiers, etc., can be used. Examples of pulverizing methods include using mortars, ball mills, sand mills, vibratory ball mills, planetary ball mills, spray mills, reverse-jet mills, vortex airflow spray mills, or sieves. Wet pulverization, which involves the presence of water or organic solvents such as hexane, can be used during pulverization. Classification methods include sieves, air classifiers, etc., which can be used in conjunction with dry or wet methods as needed.

[0066] The content of the positive electrode active material in the positive electrode active material layer 42 is preferably 50% to 99% by mass, more preferably 70% to 98% by mass, and even more preferably 80% to 95% by mass. By setting the content of the positive electrode active material within the above range, both high energy density and manufacturability of the positive electrode active material layer 42 can be achieved.

[0067] (Any ingredients)

[0068] There are no particular limitations on conductive agents, as long as they are materials that conduct electricity. Examples of such conductive agents include carbonaceous materials, metals, and conductive ceramics. Examples of carbonaceous materials include graphitized carbon, non-graphitized carbon, and graphene-based carbon. Examples of non-graphitized carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black.

[0069] Examples of carbon black include furnace black, acetylene black, and Ketjen black. Examples of graphene-based carbons include graphene, carbon nanotubes (CNTs), and fullerenes. Examples of conductive agents include powder and fibrous forms. These materials can be used alone or in combination. Furthermore, these materials can be composited. For example, a composite of carbon black and CNTs can be used. Among these, carbon black is preferred from the viewpoint of electronic conductivity and coatability, with acetylene black being the most preferred.

[0070] When using a conductive agent, the content of the conductive agent in the positive electrode active material layer 42 is preferably 1% to 10% by mass, more preferably 3% to 9% by mass. By setting the content of the conductive agent within the above range, the energy density of the secondary battery can be increased.

[0071] Examples of adhesives include fluoropolymers (such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)), thermoplastic resins such as polyethylene, polypropylene, polyacrylic acid, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers. Among these, solvent-based adhesives such as fluoropolymers (such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)) are preferred.

[0072] When using a binder, the binder content in the positive electrode active material layer 42 is preferably 1% to 10% by mass, more preferably 3% to 9% by mass. By setting the binder content within the above range, the active material can be stably maintained.

[0073] When using thickeners, examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. If the thickener has functional groups that react with lithium, these functional groups can be deactivated beforehand through methylation or similar methods.

[0074] There are no particular limitations on the filler material. When using filler material, examples include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silica, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, insoluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, and substances derived from mineral resources or their artificial forms such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica.

[0075] The positive electrode active material layer 42 may contain typical non-metallic elements such as B, N, P, F, Cl, Br, I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W as components other than positive electrode active material, conductive agent, binder, thickener, and filler.

[0076] (negative electrode)

[0077] The negative electrode 50 has a negative electrode substrate 51 and a negative electrode active material layer 52 disposed on the negative electrode substrate 51 directly or via an intermediate layer. The composition of the intermediate layer is not particularly limited, and can be selected from the composition exemplified in the positive electrode 40 described above.

[0078] In this embodiment, negative electrode active material layers 52 are overlapped on both sides of the negative electrode substrate 51.

[0079] The edge of the negative electrode active material layer 52 is positioned further outward than the edge of the positive electrode active material layer 42, which is separated by the separator 60.

[0080] The negative electrode substrate 51 is conductive. The material of the negative electrode substrate 51 can be copper, nickel, stainless steel, nickel-plated steel, aluminum, or their alloys.

[0081] Among these, copper or copper alloy is preferred. Examples of negative electrode substrate 51 include foil and vapor-deposited film; from a cost perspective, foil is preferred. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate 51. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0082] The average thickness of the negative electrode substrate 51 is preferably 2 μm to 35 μm, more preferably 3 μm to 30 μm, even more preferably 4 μm to 25 μm, and particularly preferably 5 μm to 20 μm. By making the average thickness of the negative electrode substrate 51 within the above range, the strength of the negative electrode substrate 51 can be improved, thereby increasing the energy density per unit volume of the secondary battery.

[0083] The negative electrode active material layer 52 contains a negative electrode active material. The negative electrode active material layer 52 may also contain any components such as conductive agents, binders, thickeners, and fillers, as needed. These components can be selected from the materials exemplified in the positive electrode 40 described above.

[0084] The negative electrode active material layer 52 may contain typical non-metallic elements such as B, N, P, F, Cl, Br, I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W as components other than negative electrode active material, conductive agent, binder, thickener, and filler.

[0085] As the negative electrode active material, a suitable selection can be made from known negative electrode active materials. For lithium-ion secondary batteries, materials capable of adsorbing and releasing lithium ions are typically used as the negative electrode active material. In this embodiment, the negative electrode active material is a carbonaceous material or lithium titanate. Examples of negative electrode active materials include Li₄Ti₅O. 12Lithium titanate such as Li2TiO3 and LiTiO2; carbonaceous materials such as graphite and non-graphite carbon (easily graphitized carbon or difficult-to-graphitize carbon). In the negative electrode active material layer 52, one of these materials can be used alone, or two or more can be used in combination.

[0086] In this embodiment, since the negative electrode active material is at least one of carbonaceous material or lithium titanate, the expansion of the negative electrode accompanying charging can be suppressed. Therefore, the expansion of the electrode body 2 during charging and discharging can be suppressed. Therefore, the compressive force on the inner surface of the housing 3 that causes the electrode body 2 to be compressed by the reaction force of expansion can be reduced. Therefore, the increase in the air permeability of the separator with a wet membrane can be suppressed.

[0087] "Graphite" refers to the average lattice spacing (d) of the (002) planes, determined by X-ray diffraction before or during charging and discharging. 002 The graphite material is a carbonaceous material with a wavelength greater than 0.33 nm and less than 0.34 nm. Examples of graphite include natural graphite and synthetic graphite. From the viewpoint of obtaining a material with stable physical properties, synthetic graphite is preferred.

[0088] "Non-graphitic carbon" refers to the average lattice spacing (d) of the (002) plane, as determined by X-ray diffraction before or during charging and discharging. 002 Carbonaceous materials with a wavelength of 0.34 nm to 0.42 nm can be categorized as non-graphitic carbon, including difficult-to-graphitize carbon and easily-graphitize carbon. Examples of non-graphitic carbon include materials derived from resins, petroleum asphalt or materials derived from petroleum asphalt, petroleum coke or materials derived from petroleum coke, plant-derived materials, and materials derived from alcohols.

[0089] Here, "discharge state" refers to a state in a monopolar cell where the open-circuit voltage is 0.7V or higher, using a negative electrode 50 containing carbonaceous material as the negative electrode active material as the working electrode and metallic Li as the counter electrode. The potential of the metallic Li counter electrode in the open-circuit state is essentially equal to the redox potential of Li. Therefore, the open-circuit voltage in the aforementioned monopolar cell is essentially equal to the potential of the negative electrode 50 containing carbonaceous material, which has a redox potential opposite to that of Li. In other words, an open-circuit voltage of 0.7V or higher in the aforementioned monopolar cell indicates that lithium ions that could be absorbed or released during charging and discharging have been sufficiently released from the carbonaceous material serving as the negative electrode active material.

[0090] "Difficult-to-graphitize carbon" refers to the aforementioned d 002 It is a carbonaceous material with a wavelength of 0.36 nm to 0.42 nm.

[0091] "Easily graphitizable carbon" refers to the aforementioned d 002 It is a carbonaceous material with a wavelength greater than 0.34 nm and less than 0.36 nm.

[0092] The negative electrode active material is preferably non-graphite carbon. By using non-graphite carbon as the negative electrode active material, which has a smaller expansion rate during charging, the expansion of the electrode body 2 during charging and discharging can be better suppressed. Therefore, the compressive force on the inner surface of the housing 3 that causes the electrode body 2 to be compressed by the reaction force of expansion can be better reduced. Therefore, the increase in the air permeability of the separator with a wet membrane can be better suppressed.

[0093] The negative electrode active material is typically in the form of particles (powder). The average particle size of the negative electrode active material can be, for example, set to 1 nm to 100 μm. By setting the average particle size of the negative electrode active material to the lower limit or above, the manufacture or processing of the negative electrode active material becomes easier. By setting the average particle size of the negative electrode active material to the upper limit or below, the electronic conductivity of the negative electrode active material layer is improved. To obtain powder with a specified particle size, a pulverizer, classifier, etc., can be used. The pulverization method and classification method can be selected, for example, from the methods exemplified in the positive electrode 40 described above.

[0094] The content of the negative electrode active material in the negative electrode active material layer 52 is preferably 60% to 99% by mass, more preferably 90% to 98% by mass. By setting the content of the negative electrode active material within the above range, both high energy density and manufacturability of the negative electrode active material layer 52 can be achieved.

[0095] (Isolation component)

[0096] The spacer 60 can be appropriately selected from known spacers. For example, spacers 60 consisting solely of a substrate layer, or spacers with a heat-resistant layer containing heat-resistant particles and a binder formed on one or both sides of the substrate layer, can be used. From a strength point of view, a porous resin membrane is preferred as the material of the substrate layer of the spacer 60. From a shutdown function point of view, polyolefins such as polyethylene and polypropylene are preferred as the material of the substrate layer of the spacer 60; from a resistance to oxidative decomposition point of view, polyimide and polyaromatic amide are preferred as the material of the substrate layer of the spacer 60. Materials in which these resins are combined can also be used as the substrate layer of the spacer 60.

[0097] The separator 60 has a substrate layer (separator substrate). The substrate layer of the separator 60 is a wet film.

[0098] The wet membrane of the separator can be manufactured by known manufacturing methods. The following shows an example of a manufacturing method for a separator formed solely from a wet membrane as a substrate layer.

[0099] For example, polymers such as polyethylene and polypropylene, along with desired additives and extractants such as liquid paraffin, are mixed and heated to melt. The melt is ejected, for example, from a T-die and cast onto a temperature-controlled cooling roller. This forms a sheet where the polymer and liquid paraffin have separated into phases. The sheet is then placed on a biaxial stretching machine and biaxially stretched at a specified elongation to form a film. Biaxial stretching can be performed simultaneously or separately. The film is placed in a solvent (e.g., dichloromethane, methyl ethyl ketone, etc.) to dissolve the extractants in the film, and the extractants are extracted and removed. The film is then dried to remove the solvent. Next, the film is guided to a TD stretching heat-fixing machine and heat-fixed at a specified temperature to produce a wet film.

[0100] The pores of the wet membrane manufactured in the above manner are formed by extracting and removing the extractant. Therefore, the pores of the wet membrane can be formed in a three-dimensional manner, regardless of the membrane's thickness or planar direction. Consequently, the pores of the wet membrane are more easily damaged when subjected to compressive forces in the thickness direction, for example, compared to the pores of a dry membrane. Therefore, the permeability of a separator with a wet membrane tends to increase after being subjected to compressive forces.

[0101] It should be noted that the air permeability of the separator 60 can be measured, for example, according to JIS P-8117. For example, using a Görle breathability meter, the air permeability (seconds / 100cc) is measured as the time (seconds) it takes for 100cc of air to pass through a circle of a specified area.

[0102] For the heat-resistant particles contained in the heat-resistant layer, it is preferable that the mass reduction is 5% or less when heated from room temperature to 500°C in an air atmosphere at 1 atm, and the mass reduction is further preferably 5% or less when heated from room temperature to 800°C in an air atmosphere at 1 atm. Inorganic compounds can be cited as materials for which the mass reduction during heating is less than the specified value. 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 aluminosilicates; 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; insoluble ionic crystals such as calcium fluoride and barium fluoride; covalently bonded crystals such as silicon and diamond; and substances derived from mineral resources or their artificial products such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica. As inorganic compounds, these substances, either as elements or in combination, can be used alone, or two or more can be mixed. Among these inorganic compounds, from the viewpoint of the safety of the energy storage element 1, silicon oxide, aluminum oxide, or aluminosilicates are preferred.

[0103] From a strength perspective, the porosity of the separator 60 is preferably 80% by volume or less, and from a discharge performance perspective, it is preferably 20% by volume or more. Here, "porosity" is a volume-based value, referring to the value measured using a mercury porosimeter.

[0104] (isolation material)

[0105] like Figure 2 and Figure 3 As shown, the separator 70 is disposed between the inner surface of the housing 3 (housing body 31) and the electrode body 2, and is housed inside the housing 3. Figure 1 (The spacer 70 is not shown in the diagram). The spacer 70 may be in the shape of a sheet, for example. Two spacers 70 may also be housed within the housing 3.

[0106] Two spacers 70, 70 can be disposed within the housing 3, for example, by contacting the flat outer surfaces of the two sides of the flat electrode body 2. The spacers 70 can be fixed to the inner surface of the housing by adhesive or heat fusion, or they can be held by pressure from both sides by simply clamping the electrode body 2 and the inner surface of the housing.

[0107] For example, the entire surface of one side of the sheet-like spacer 70 may be fixed to the inner surface of the housing (surface bonding, etc.), or a portion of one side of the sheet-like spacer 70 may be fixed to the inner surface of the housing, for example, by point bonding.

[0108] The energy storage element 1 of this embodiment may have an insulating sheet 80 disposed inside the housing 3 to insulate the electrode body 2 from the housing 3 and to cover the inner surface of the housing body 31. The insulating sheet 80 is, for example, made of resin. The insulating sheet 80 is disposed between the inner surface of the housing body 31 and the electrode body 2. The insulating sheet 80 may be disposed to cover the electrode body 2.

[0109] The material of the insulating sheet 80 is not particularly limited as long as it is electrically insulating (non-conductive). For example, it can be made of polyolefin resins such as polyethylene and polypropylene, or resins such as polyimide resin or polyamide resin. From the viewpoint of ease of manufacture, the material of the insulating sheet 80 is preferably polyolefin resin, and more preferably at least one of polyethylene (PE) and polypropylene (PP).

[0110] The insulating sheet 80 is formed into a bag shape by bending sheet-like components or fusing or welding multiple sheet-like components, and is disposed within the housing body 31.

[0111] It should be noted that the spacer 70 can be fixed to the insulating sheet 80 by the same surface bonding or spot bonding as described above. Preferably, the spacer 70 and the insulating sheet 80 fixed in this manner are made of the same material. By using the same material, the spacer 70 and the insulating sheet 80 can be easily fixed together by surface bonding or spot bonding.

[0112] The size of the spacer 70 is not particularly limited, as long as it can be accommodated within the housing 3. Figure 3 As shown, when the flat electrode body 2 and the spacer 70 are housed within the housing 3 in the thickness direction of the electrode body 2, the size of a single sheet-like spacer 70 can be smaller than or equal to the size of the electrode body 2. In this case, the spacer 70 can be disposed within the housing 3 such that one side of the sheet-like spacer 70 is entirely in contact with the flat outer surface of the flat electrode body 2.

[0113] Similarly, as Figure 3 When viewing the electrode body 2 and the separator 70 as shown, the area of ​​the separator 70 can be 0.6 or more of the area of ​​the electrode body 2, preferably 0.8 or more.

[0114] By making the size of the separator 70 within the range described above, the space z of the winding center portion of the electrode body 2 can be reduced more effectively.

[0115] It should be noted that, as Figure 3 When viewing the electrode body 2 and the separator 70 as shown, the area of ​​the separator 70 can be less than 1.0 times the area of ​​the electrode body 2.

[0116] In the flat electrode body 2, the positive electrode active material layer 42 and the negative electrode active material layer 52 are positioned opposite each other with a separator 60 between them. In the winding axis direction of the electrode body 2, the two edges of the negative electrode active material layer 52 are positioned further outward than the two edges of the positive electrode active material layer 42. In other words, the two ends of the negative electrode active material layer 52 in the winding axis direction have portions that are not opposite to the positive electrode active material layer 42.

[0117] Therefore, when viewed from the thickness direction, the flat electrode body 2 has opposing regions where the positive electrode active material layer 42 and the negative electrode active material layer 52 face each other. Preferably, the length of the separator 70 in the winding axis direction is greater than or equal to the length of the opposing regions, and the separator 70 is arranged in such a way that it completely covers the opposing regions in the winding axis direction. In other words, the two edges of the separator 70 in the winding axis direction preferably overlap with the two edges of the opposing regions or protrude further outward than the two edges of the opposing regions when the electrode body is viewed from the thickness direction.

[0118] With this configuration, the distance between the positive electrode active material layer 42 and the negative electrode active material layer 52 can be more effectively suppressed by the separator 70. Therefore, uneven charging and discharging reactions in the energy storage element can be suppressed.

[0119] The flat, coiled electrode body 2 has a flat portion 21 where sheet-like positive electrodes 40 and negative electrodes 50 are overlapped in a flat state, and a folded portion 22 where the overlapped sheet-like positive electrodes 40 and negative electrodes 50 are folded. In the folded portion 22, the positive electrodes 40 and negative electrodes 50 are bent around a winding axis. When viewed from the winding axis direction, the electrode body 2 has folded portions 22 at both ends of the flat portion 21. In the portion of the flat portion 21 where the overlapped positive electrodes 40 and negative electrodes 50 begin to bend along the winding circumferential direction, there is a boundary portion y (refer to...). Figure 2 and Figure 3 The boundary portion y exists at 4 locations in a straight line extending in the direction of the winding axis.

[0120] When viewed from the winding axis direction, the flat, wound electrode body 2 is preferably positioned such that the two edges of the spacer 70 are located further inward than the boundary portion y between the flat portion 21 and the folded portion 22. In other words, the spacer 70 is preferably positioned in such a way that the boundary portion y between the flat portion 21 and the folded portion 22 is not subjected to direct compressive force through the spacer 70.

[0121] The boundary portion y between the flat portion 21 and the folded portion 22 is a portion that is difficult to compress even when subjected to compressive force in the thickness direction of the electrode body 2. In other words, the flat portion 21 is more prone to compressive deformation than the boundary portion y between the flat portion 21 and the folded portion 22. Therefore, by positioning the edge of the separator 70 closer to the inside than the boundary portion y between the flat portion 21 and the folded portion 22, the separator 70 can more easily apply a compressive force to the electrode body 2 from the outside.

[0122] The shape of the spacer 70 is as described above, for example, sheet-like, preferably a flat plate without any bent or twisted portions. By making the spacer 70 flat, the number of sheets or the thickness of the spacer 70 can be easily changed according to the tolerance (difference relative to the reference size) of the internal space of the electrode body 2 or the housing 3. Therefore, it is possible to appropriately adjust to the desired standard design, and thus it is easy to reduce the space z of the winding center portion.

[0123] The material of the separator 70 is not particularly limited. The separator 70 can be, for example, a resin product such as polyethylene, polypropylene or other polyolefin resins, polyimide resin or polyamide resin. Based on its good stability to the electrolyte, and also based on its ease of handling, the material of the separator 70 is preferably a polyolefin resin such as polyethylene (PE) or polypropylene (PP).

[0124] The separator 70 is harder than the separator 60 (the substrate layer of the wet membrane). The hardness can be quantified by measuring the displacement of the separator 70 and the separator 60 when compressed under a specified load (details below).

[0125] The smaller the displacement, the stiffer the material; the larger the displacement, the softer the material. Therefore, the displacement in the spacer 70 is smaller than the displacement in the spacer 60.

[0126] As described above, the separator 70 is harder than the separator 60, and therefore the separator 70 is less prone to deformation. Thus, when the inner surface of the housing compresses the electrode body 2 through the separator 70 due to the reaction force during the expansion of the electrode body 2, the separator 70 can better suppress the outward expansion of the electrode body 2. Therefore, expansion is more likely to occur inward, reducing the space z at the center of the coiled portion of the electrode body 2.

[0127] The hardness values ​​of the spacer 70 and the spacer 60 can be quantified using methods such as those described below, or the hardness difference can also be quantified.

[0128] Specifically, when the separator 70 and the separator 60 are compressed under a load of 7 kN, the displacement of the separator 60 can be greater than or equal to the displacement of the separator 70. It should be noted that the difference in displacement can be less than or equal to 0.3 mm / mm.

[0129] As described above, by making the difference in displacement greater than 0.1 mm / mm, the separator 70 is made harder than the separator 60. Therefore, based on the above reasons, the outward expansion of the electrode body 2 can be better suppressed.

[0130] It should be noted that the displacement mentioned above is expressed in units of 1 mm thickness. Therefore, the thickness of the separator 70 or the separator 60 when measuring the displacement can be different, as long as they are basically the same thickness.

[0131] For example, multiple insulating sheets 70 or insulating elements 60 can be overlapped to apply a load of 7kN with a total thickness of approximately 1mm to 2mm. The area of ​​the pressure head when applying the load can be 3000mm². 2 The above can be 4000mm 2 The surface area of ​​the pressure head is preferably 3680 mm². 2 .

[0132] It should be noted that the spacer 70 can be arranged in two in the housing 3 as described above, in a way that clamps the electrode body 2, or it can be arranged in the housing 3 in a way that only contacts the flat part (one side of the flat part) of the flat electrode body 2.

[0133] The housing 3 can house the electrode body 2 in the internal space as described above and be held in a way that makes it a fixed size.

[0134] "Energy storage elements that are held in a fixed size" are provided, for example, in an energy storage device 100 in which multiple energy storage elements 1 are arranged in a manner that faces one side.

[0135] Whether the energy storage element 1 in the energy storage device 100 is held in a fixed size can be determined by comparing it with an energy storage device 100 of the same design. An energy storage device 100 of the same design means an energy storage device 100 that is configured such that the number of multiple energy storage elements 1 arranged facing one side is the same as that of the energy storage device being compared, and the fixture for fixing the multiple energy storage elements 1 in a predetermined position is of the same shape as that of the energy storage device being compared.

[0136] When the difference in total length between the energy storage device 100 and the energy storage device 100 designed in the same manner is less than 3%, the energy storage elements 1 in the energy storage device 100 are each held in a fixed size manner. Here, the energy storage device 100 designed in the same manner and the energy storage device 100 being compared are properly discharged in a manner in which the voltage of the energy storage device 100 is the same.

[0137] It should be noted that when the energy storage device 100 is composed of a single energy storage element 1 and a fixing device, it is also possible to determine whether the energy storage element 1 is held in a fixed size by comparing it with an energy storage device 100 of the same design.

[0138] The energy storage element 1 that is held in a fixed size is, for example, each energy storage element 1 that constitutes the energy storage device as described above.

[0139] When the energy storage element 1 constituting the energy storage device 100 is held in a fixed size, it is difficult to individually adjust the pressure applied to each energy storage element. Therefore, a relatively large pressure is applied to the energy storage element 1. As a result, the pores of the wet membrane of the insulating member 60 included in the electrode body 2 are easily damaged, and the air permeability of the insulating member 60 easily increases.

[0140] In this embodiment, the flat electrode 2 is disposed within the housing 3 in such a way that there is no gap between it and the inner surface of the housing 3 in the thickness direction. Preferably, the housing 3 is one that is difficult to expand. In other words, in order to hold the energy storage element 1 at a fixed size, the housing 3 is preferably one whose volume increase rate after housing the electrode 2 is less than a predetermined percentage (e.g., less than 10%) compared to before housing. The difference between the length of the housing before housing the flat electrode 2 and the length of the housing after housing (the length of the housing in the thickness direction of the electrode 2) can be less than 20%. Such a housing 3 is, for example, a square-shaped (cubic prism-shaped) housing 3 made of a metal plate with a thickness of 0.3 mm or more. This housing 3 can be made of a metal plate with a thickness of 1.5 mm or less. Examples of such metals include aluminum (including aluminum alloys) and stainless steel.

[0141] By making the housing 3 difficult to expand, the electrode body 2 housed within the housing 3 is compressed from the outside. If the electrode body 2 is compressed from the outside, the space z of the coiled central portion of the electrode body 2 becomes narrow.

[0142] In the energy storage element 1 of this embodiment, with the flat electrode body 2 and the separator 70 housed in the housing 3, the preferred proportion of the electrode body 2 and the separator 70 in the thickness direction of the central portion of the electrode body 2 is as follows.

[0143] Specifically, the cross-section obtained by cutting the energy storage element 1 (with the electrode body 2 housed in the housing 3) in a plane perpendicular to the winding axis direction of the electrode body 2 is ( Figure 2 In the cross-section shown, the thickness (A) of the electrode body 2, the total thickness (B) of the separator 70, and the distance (C) between the opposing inner surfaces within the housing body 31 preferably satisfy the following relationship.

[0144] 0.95C≤A+B≤1.00C

[0145] B / A = 0.01~0.08

[0146] A / C = 0.90~0.99

[0147] B / C = 0.01~0.08

[0148] (Non-aqueous electrolyte)

[0149] As a non-aqueous electrolyte, a suitable selection can be made from known non-aqueous electrolytes. Non-aqueous electrolyte solutions can also be used. A non-aqueous electrolyte solution comprises a non-aqueous solvent and an electrolyte salt dissolved in that non-aqueous solvent.

[0150] As a non-aqueous solvent, a suitable selection can be made from known non-aqueous solvents. Examples of non-aqueous solvents include cyclic carbonates, chain carbonates, carboxylic acid esters, phosphate esters, sulfonates, ethers, amides, and nitriles. Solvents in which some of the hydrogen atoms in these compounds are replaced by halogens can also be used as non-aqueous solvents.

[0151] Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butene carbonate (BC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), chloroethylene carbonate, fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), styrene carbonate, 1-phenylethylene carbonate, and 1,2-diphenylethylene carbonate. Among these, EC or PC are preferred.

[0152] Examples of chain carbonates include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diphenyl carbonate, trifluoroethyl methyl carbonate, and bis(trifluoroethyl) carbonate. Among these, DMC or EMC is preferred.

[0153] As a non-aqueous solvent, cyclic carbonates or chain carbonates are preferred, and more preferably, a combination of cyclic and chain carbonates. Using cyclic carbonates promotes the dissociation of electrolyte salts, thereby increasing the ionic conductivity of the non-aqueous electrolyte. Using chain carbonates helps to keep the viscosity of the non-aqueous electrolyte low. When using a combination of cyclic and chain carbonates, the volume ratio of cyclic carbonate to chain carbonate (cyclic carbonate: chain carbonate) is preferably set, for example, in the range of 5:95 to 50:50.

[0154] As electrolyte salts, appropriate choices can be made from well-known electrolyte salts. Examples of electrolyte salts include lithium salts, sodium salts, potassium salts, and magnesium salts. Salts, etc. Among these, lithium salts are preferred.

[0155] Examples of lithium salts include inorganic lithium salts such as LiPF6, LiPO2F2, LiBF4, LiClO4, and LiN(SO2F)2, and lithium salts with halogenated hydrocarbon groups such as LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, and LiC(SO2C2F5)3. Among these, inorganic lithium salts are preferred, and LiPF6 is more preferred.

[0156] The electrolyte salt content in the non-aqueous electrolyte is preferably 0.1 mol / dm³ at 20°C and 1 atmosphere. 3 ~2.5mol / dm 3 More preferably 0.3 mol / dm3 ~2.0 mol / dm 3 Further preferably 0.5 mol / dm 3 ~1.7mol / dm 3 The preferred value is 0.7 mol / dm³. 3 ~1.5mol / dm 3 By maintaining the electrolyte salt content within the aforementioned range, the ionic conductivity of the non-aqueous electrolyte can be improved.

[0157] In addition to non-aqueous solvents and electrolyte salts, non-aqueous electrolytes may also contain additives. Examples of additives include halogenated carbonates such as fluoroethylene carbonate (FEC) and difluoroethylene carbonate (DFEC); oxalates such as lithium bis(oxalate)borate (LiBOB), lithium difluorooxalate borate (LiFOB), and lithium bis(oxalate)difluorophosphonate (LiFOP); imide salts such as lithium bis(fluorosulfonyl)imide (LiFSI); aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrides of terphenyl, cyclohexylbenzene, tert-butylbenzene, tert-amylbenzene, diphenyl ether, and dibenzofuran; partially halogenated compounds of the above aromatic compounds such as 2-fluorobiphenyl, o-cyclohexylfluorobenzene, and p-cyclohexylfluorobenzene; and halogenated benzenes such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole. Dimethyl ether compounds; vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, pentenic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride; vinyl sulfite, propylene sulfite, dimethyl sulfite, propane sulfonate lactone, propylene sulfonate lactone, butane sulfonate lactone, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, ethylene sulfate, sulfolane, dimethyl sulfone, diethyl sulfoxide, diethyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfide, 4,4'-bis(2,2-dioxa-1,3,2-dioxathiacyclopentane), 4-methylsulfonyloxymethyl-2,2-dioxa-1,3,2-dioxathiacyclopentane, thioanisole, diphenyl disulfide, dipyridine Disulfides, perfluorooctane, trimethylsilane borate, trimethylsilane phosphate, tetramethylsilane titanate, lithium monofluorophosphate, lithium difluorophosphate, etc. These additives can be used alone or in combination of two or more.

[0158] The content of additives in the non-aqueous electrolyte relative to the total mass of the non-aqueous electrolyte is preferably 0.01% to 10% by mass, more preferably 0.1% to 7% by mass, even more preferably 0.2% to 5% by mass, and particularly preferably 0.3% to 3% by mass. By setting the content of additives within the above range, the capacity maintenance performance or cycle performance after high-temperature storage can be improved, and the safety can be further enhanced.

[0159] The shape of the energy storage element 1 in this embodiment is not particularly limited. Examples include cylindrical batteries, laminated film batteries, square batteries, flat batteries, coin-shaped batteries, and button batteries.

[0160] Figure 1 The diagram shows an energy storage element 1 (non-aqueous electrolyte energy storage element) as an example of a square battery. An electrode body 2, having a positive electrode 40 and a negative electrode 50 wound around a clamping separator 60, is housed in a square casing 3 (container). The positive electrode 40 is electrically connected to the positive terminal 4 via a positive lead 45. The negative electrode 50 is electrically connected to the negative terminal 5 via a negative lead 55.

[0161] <Composition of Non-Aqueous Electrolyte Storage Devices>

[0162] In this embodiment, the energy storage element 1 serves as an energy storage unit 10 (battery module) composed of multiple energy storage elements 1, and can be installed in power supplies for automobiles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), as well as power supplies for electronic devices such as personal computers and communication terminals, or power storage devices. In this case, the technology of the present invention can be applied to at least one energy storage element 1 included in the energy storage device 100.

[0163] Figure 5 The diagram shows an example of an energy storage device 100 formed by further assembling energy storage units 10 composed of two or more electrically connected energy storage elements 1. The energy storage device 100 may include busbars (not shown) electrically connecting two or more energy storage elements 1, busbars (not shown) electrically connecting two or more energy storage units 10, etc. The energy storage unit 10 or the energy storage device 100 may include a status monitoring device (not shown) for monitoring the status of one or more energy storage elements 1.

[0164] It should be noted that the energy storage device 100 may have multiple fasteners for fixing the energy storage element 1 in a specific position. The energy storage element 1 in the energy storage device 100 is fixed by these fasteners, thereby maintaining it at a fixed size.

[0165] For example, the energy storage device 100 may include a pair of end plates arranged to clamp a plurality of energy storage elements 1, 1 arranged in one direction from both ends of the arrangement direction, and a membrane connecting the pair of end plates. Thus, the energy storage elements 1 can be held in a fixed size as described above.

[0166] <Manufacturing Method of Non-Aqueous Electrolyte Storage Components>

[0167] The manufacturing method of the energy storage element 1 in this embodiment can be appropriately selected from known methods. This manufacturing method includes, for example, a step of preparing an electrode body 2, a step of preparing a non-aqueous electrolyte, and a step of housing the electrode body 2 and the non-aqueous electrolyte in a housing 3. The step of preparing the electrode body 2 includes: preparing a positive electrode 40 and a negative electrode 50, and stacking or winding the positive electrode 40 and the negative electrode 50 through a separator 60 to form the electrode body 2.

[0168] The non-aqueous electrolyte can be housed in the housing 3 by a suitable method from known sources. For example, when using a non-aqueous electrolyte, the injection port can be sealed after injecting the non-aqueous electrolyte through the injection port formed on the housing 3.

[0169] <Other Implementation Methods>

[0170] It should be noted that the energy storage element of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, structures of other embodiments can be added to the structure of a certain embodiment, or a part of the structure of a certain embodiment can be replaced with structures of other embodiments or known technologies. Furthermore, a part of the structure of a certain embodiment can also be deleted. In addition, known technologies can be added to the configuration of a certain embodiment.

[0171] In the above embodiments, the case where the energy storage element 1 is used as a rechargeable non-aqueous electrolyte secondary battery (e.g., a lithium-ion secondary battery) has been described, but the type, shape, size, capacity, etc., of the energy storage element are arbitrary. This invention can be applied to various secondary batteries, double-layer capacitors, or lithium-ion capacitors, etc.

[0172] Example

[0173] The present invention will now be further described in detail with reference to embodiments. The present invention is not limited to the following embodiments.

[0174] As shown below, non-aqueous electrolyte secondary batteries (lithium-ion secondary batteries) of various embodiments and comparative examples are manufactured.

[0175] <Battery Manufacturing>

[0176] On both sides of a 12μm thick aluminum foil, a positive electrode active material layer with a single-sided thickness of 81μm is formed (the positive electrode active material is a lithium transition metal composite oxide (LiNi)). 1 / 3 Co 1 / 3 Mn 1 / 3 O2)) is used to create the positive electrode.

[0177] A negative electrode is fabricated by forming a single-sided negative electrode active material layer with a thickness of 78 μm on both sides of an 8 μm thick copper foil (the negative electrode active material is non-graphitizable carbon, graphite or silicon as shown in Table 1).

[0178] By using a 20μm thick polyethylene wet film as a substrate layer separator, the positive and negative electrodes are overlapped and further wound to create a wound electrode body with dimensions of 116mm in width, 10.6mm in thickness, and 57mm in height.

[0179] Next, two spacers, each 0.15 mm thick and 96.0 mm wide x 56.3 mm high, are placed inside the main body of the housing (120 mm wide, 12.5 mm thick (with an internal thickness spacing of 11.5 mm), and 65 mm high). The two spacers are positioned inside the housing body such that the flat electrode is held in place by the two spacers from both sides when inserted into the housing body. Then, the electrode is inserted into the housing body with each flat surface in contact with one of the spacers, and the housing is sealed.

[0180] It should be noted that the non-aqueous electrolyte was prepared as follows: LiPF6 was dissolved in a non-aqueous solvent to a salt concentration of 1.2 mol / L, thereby preparing the non-aqueous electrolyte. Then, it was appropriately injected into the casing according to the following measurements. Here, as the non-aqueous solvent, in Example 1 and Comparative Example 2, a solvent in which propylene carbonate (PC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a PC:DMC:EMC ratio of 30:35:35 (volume %) was used. In Example 2 and Comparative Example 1, a solvent in which ethylene carbonate (EC), DMC, and EMC were mixed in a EC:DMC:EMC ratio of 30:35:35 (volume %) was used.

[0181] <Determination of the hardness of separators and separator components used in battery manufacturing>

[0182] With 10 sheets of 0.15mm thick spacer overlapped, the surface area of ​​3680mm² was measured using an Autograph universal testing machine (manufactured by Shimadzu Corporation, AG-X). 2 The displacement is calculated when a 7kN load is applied to the indenter and held for 1 minute. The displacement is then calculated relative to a thickness of 1mm.

[0183] As a result, the displacement (relative to 1 mm) of the spacer (solid polypropylene) used in Examples 1, 2 and Comparative Example 1 was 0.10 mm / mm.

[0184] The displacement (relative to 1 mm) of the separator (porous polyurethane) used in Comparative Example 2 was 0.77 mm / mm.

[0185] On the other hand, using an Autograph universal testing machine (manufactured by Shimadzu Corporation, AG-X) with 50 overlapping spacers of 20μm thickness (0.020mm) as a reference, the surface area of ​​3680mm² was measured. 2 The displacement is measured when a load of 7 kN is applied to the indenter and held for 1 minute. This measured value is taken as the displacement relative to a thickness of 1 mm.

[0186] As a result, the displacement of the spacer used in each embodiment and comparative example (relative to 1 mm) is 0.21 mm / mm.

[0187] (Examples 1 and 2)

[0188] Lithium-ion secondary batteries were manufactured using the negative electrode active materials shown in Table 1 in the manner described above. It should be noted that the separators and separators are the same as those in Examples 1 and 2.

[0189] (Compare Examples 1 and 2)

[0190] Lithium-ion secondary batteries are manufactured in the manner described above using the negative electrode active material, separator, and separator shown in Table 1.

[0191] In Comparative Example 1, the same separators and separators as those in Example 1 were used. However, a different negative electrode active material was used as the negative electrode active material compared to that in Example 1.

[0192] In Comparative Example 2, a porous material (of the same size) different from that in Example 1 was used as the separator.

[0193] The lithium-ion secondary batteries of Examples 1 and 2, and Comparative Examples 1 and 2, were evaluated as described later, and the results are shown in Table 1.

[0194] [Table 1]

[0195]

[0196] <Determination of the spatial width of the winding center portion of the electrode>

[0197] The housing is held at a fixed size such that the size of the housing after the electrode body is inserted is the same as the size before the electrode body is inserted. In this state, an X-ray CT image of the central portion of the wound electrode body is obtained using an X-ray CT scanning device (Shimadzu Corporation Micro Focus X-ray CT system inspeXio SMX-225CT FRD HR Plus). It should be noted that the obtained X-ray CT image is a cross-section obtained by cutting with a plane perpendicular to the direction in which the folds in the wound electrode body are connected to each other. In other words, the obtained image is a cross-section with the direction of the folds in the wound electrode body connected to each other. Figure 2 The cross-section when the electrode body is cut along the virtual plane in the vertical direction.

[0198] In the acquired X-ray CT images, image processing was performed on a 1mm wide region ranging from 34.5mm to 35.5mm from the edge of the negative electrode active material layer inwards. Specifically, the image was binarized to distinguish the space between the electrode and the spacer portion and the coiled center portion of the electrode body in this region.

[0199] The number of pixels in the space that appears as black after binarization is counted to calculate the spatial width of the center portion.

[0200] It should be noted that the spatial amplitude (size of the space) is calculated using a conversion value such as 1 pixel = 77 μm (1 mm = 13 pixels). For example, when the number of pixels counted is 200 pixels, the spatial width is (200 / 13) × 0.077 = 1.185 mm.

[0201] <Determination of the reaction force applied in conjunction with the expansion of the electrode>

[0202] Using a clamp equipped with a weighing sensor (LCX-A-ID manufactured by Kyowa Electric Co., Ltd.), the battery after acquiring X-ray CT images is held with the long side of the housing in contact with the clamp. At this time, the housing size with the electrodes housed is the same as the housing size before housing the electrodes. Then, constant current charging is performed until the utilization rate of the negative electrode active material reaches 0.5, thus entering a charging state. It should be noted that the capacity of the negative electrode active material is the value when the utilization rate is 1.0, which is 372 mAh / g in the case of non-graphitizable carbon, 372 mAh / g in the case of graphite, and 4200 mA / g in the case of Si.

[0203] The value measured by the weighing sensor is used as the reaction force applied to the electrode body during the charging state.

[0204] <Determination of the rate of increase in air permeability of the isolation component>

[0205] In addition to the battery manufactured as described above, the following are also prepared: an electrode body (with a wet membrane separator) of the battery designed in the same way as in Example 1, and an electrode body with a 20 μm thick dry membrane (a 3-layer structure of polypropylene / polyethylene / polypropylene) instead of the separator in Example 1.

[0206] Using the Autograph universal testing machine (AG-X manufactured by Shimadzu Corporation), apply a specified load (various loads) to each electrode body in its uninserted state for 1 minute, disassemble the electrode body after applying the load, and measure the air permeability of the insulating component.

[0207] The air permeability of the isolation components before the application of load (unused isolation components not used in the fabrication of the electrode body) was taken as 100%, and the air permeability of each isolation component after the application of load was calculated as a relative value. The results are shown in Tables 2 and 3.

[0208] Based on the coordinate graph showing the relationship between the calculated air permeability ratios and the load, an approximate curve (quadratic function, with the slice set to 100) is created using the least squares method.

[0209] The reaction force applied to the electrode body during charging is assumed to be the pressure applied to the separator. Using the above approximate curve, the air permeability ratio of the separator when subjected to the above reaction force is obtained. Subtracting 100% from this air permeability ratio, the air permeability increase rate of each cell is calculated (refer to Table 1).

[0210] [Table 2]

[0211] <Wet film>

[0212] Load[kN] 0 4 6 8 10 19 <![CDATA[Air permeability [sec·100cc -1 > 85.0 85.3 87.0 86.7 88.3 99.7 Air permeability ratio [%) 100.0 100.4 102.4 102.0 103.9 117.3

[0213] [Table 3]

[0214] Dry membrane

[0215] Load[kN] 0 4 6 8 10 15 19 <![CDATA[Air permeability [sec·100cc -1 > 164.0 163.5 163.0 163.5 164.0 164.0 164.5 Air permeability ratio [%) 100.0 99.7 99.4 99.7 100.0 100.0 100.3

[0216] As shown in Table 1, in the energy storage element of this embodiment, the space of the winding center portion of the electrode body is small, and the increase in the air permeability of the separator with a wet membrane can be suppressed.

[0217] It should be noted that, as shown in Tables 2 and 3, in energy storage elements (batteries) with a separator having a wet membrane as the substrate layer, the air permeability of the separator tends to increase compared to energy storage elements with a dry membrane separator.

Claims

1. An energy storage element, comprising: A wound electrode body having a negative electrode containing a negative electrode active material, a positive electrode, and a separator disposed between the positive electrode and the negative electrode. The housing that houses the electrode body, and An isolator is disposed inside the housing between the electrode body and the inner surface of the housing; The separator has a wet membrane. The negative electrode active material is a carbonaceous material or lithium titanate. The separator is harder than the separator. The isolation material and the isolation member are respectively measured with a surface area of ​​3680 mm². 2 When the pressure head is compressed with a load of 7kN, the displacement of the isolation member is more than 0.1mm / mm greater than the displacement of the isolation object.

2. The energy storage element according to claim 1, wherein, The negative electrode active material is non-graphitic carbon, which is used as the carbonaceous material.

3. The energy storage element according to claim 1 or 2, wherein, The housing is held in a way that makes it a fixed size.

4. The energy storage element according to any one of claims 1 to 3, comprising an insulating sheet covering the electrode body and insulating the electrode body from the housing. The casing is made of metal. The separator is disposed between the electrode body and the insulating sheet.

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