Single cells and battery modules

Abstract

To provide a single cell that prevents wear of collectors and prevents the occurrence of electrolyte leakage.SOLUTION: A single cell has: a lamination unit composed of a set of a positive electrode collector, a positive electrode active material layer, a separator, a negative electrode active material layer, and a negative electrode collector, which are laminated in order; and an annular frame member that is arranged around the positive electrode active material layer and the negative electrode active material layer between the positive electrode collector and the negative electrode collector. The ratio of an electrode part thickness obtained by adding up the thicknesses of the positive electrode collector, the positive electrode active material layer, the separator, the negative electrode active material layer, and the negative electrode collector to a frame part thickness obtained by adding up the thicknesses of the positive electrode collector, the frame member, the separator, and the negative electrode collectors (electrode part thickness / frame part thickness) is 1.0-5.3.SELECTED DRAWING: Figure 3

Description

[Technical Field] 【0001】 This invention relates to a single cell and a battery module. [Background technology] 【0002】 Lithium-ion batteries are rechargeable batteries that can achieve high energy density and high power density, and have been widely used in various applications in recent years. A typical lithium-ion battery is constructed by first providing a positive electrode active material layer and a negative electrode active material layer on one side of a current collector, then sandwiching a separator between the active material layers to stack the positive electrode active material and the negative electrode active material, and sealing the outer edges of the positive electrode current collector, separator, and negative electrode current collector with a frame member to produce a roughly flat lithium rechargeable single cell, and stacking multiple such single cells. 【0003】 In a lithium-ion battery formed by stacking multiple single cells, if there is a difference between the electrode thickness, which is the sum of the thicknesses of the positive electrode current collector, positive electrode active material layer, separator, negative electrode active material layer, and negative electrode current collector of each single cell, and the frame thickness, which is the sum of the thicknesses of the positive electrode current collector, frame member, separator, and negative electrode current collector (i.e., the electrode thickness is considerably larger than the frame thickness), pressure is applied to the inner edge of the frame during stacking, and current concentrates in this area, making it easy for the current collector to wear down and electrolyte leakage to occur. 【0004】 To prevent such electrolyte leakage, methods have been proposed for bipolar batteries in which multiple lithium secondary single cells are stacked in the stacking direction of the positive and negative electrodes, and in a plan view of the bipolar battery, the sealing layer is exposed to the outside of the single cell, and furthermore, adjacent sealing layers in the stacking direction are bonded to each other (see Patent Document 1), and for single cells in which an electrolyte absorber is provided in the frame (see Patent Document 2). [Prior art documents] [Patent Documents] 【0005】 [Patent Document 1] Japanese Patent Publication No. 2005-190713 [Patent Document 2] Japanese Patent Application Laid-Open No. 2018-125213 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0006】 However, for the purpose of increasing the energy capacity, as the area of a single cell increases and the number of stacked layers increases, even with these measures, there has been a problem that electrolyte leakage occurs at the inner edge of the frame portion. 【0007】 The present invention has been made in view of the above problems, and an object thereof is to provide a single cell that suppresses the loss of a current collector and does not cause electrolyte leakage. 【Means for Solving the Problems】 【0008】 As a result of intensive studies, the present inventors have reached the present invention. That is, the present invention is a single cell having a stacked unit composed of a set of a positive electrode current collector, a positive electrode active material layer, a separator, a negative electrode active material layer, and a negative electrode current collector stacked in order, and an annular frame member disposed around the positive electrode active material layer and the negative electrode active material layer between the positive electrode current collector and the negative electrode current collector, and a ratio (electrode portion thickness / frame portion thickness) of the total thickness of the electrode portions obtained by summing the thicknesses of each of the positive electrode current collector, the positive electrode active material layer, the separator, the negative electrode active material layer, and the negative electrode current collector to the total thickness of the frame portions obtained by summing the thicknesses of each of the positive electrode current collector, the frame member, the separator, and the negative electrode current collector is 1.0 to 5.3, and relates to a battery module formed by stacking single cells. 【Effects of the Invention】 【0009】 According to the present invention, it is possible to provide a single cell that suppresses the loss of a current collector and does not cause electrolyte leakage. 【Brief Description of the Drawings】 【0010】 [Figure 1] FIG. 1 is a partially cutaway perspective view schematically showing an example of the configuration of a lithium ion battery as a single cell. [Figure 2]Figure 2 is an enlarged cross-sectional view of the single cell shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view schematically showing an example of a single cell with different electrode part thickness / frame part thickness. [Figure 4] Figure 4 is a cross-sectional view schematically showing an example of a single cell with different electrode part thickness / frame part thickness. [Figure 5] Figure 5 is a cross-sectional view schematically showing an example of a single cell with different electrode part thickness / frame part thickness. [Figure 6] Figure 6 is a top view of the single cell shown in Figure 1. [Figure 7] Figure 7 is a cross-sectional view schematically showing an example of a battery module. 【Mode for Carrying Out the Invention】 【0011】 Hereinafter, the present invention will be described in detail. In this specification, when referring to a lithium ion battery, it is a concept that also includes a lithium ion secondary battery. 【0012】 The single cell of the present invention is a single cell having a laminated unit composed of a set of a positive electrode current collector, a positive electrode active material layer, a separator, a negative electrode active material layer, and a negative electrode current collector laminated in order, and an annular frame member disposed around the positive electrode active material layer and the negative electrode active material layer between the positive electrode current collector and the negative electrode current collector, wherein the ratio (electrode part thickness / frame part thickness) of the total thickness of each of the positive electrode current collector, the positive electrode active material layer, the separator, the negative electrode active material layer, and the negative electrode current collector to the total thickness of each of the positive electrode current collector, the frame member, the separator, and the negative electrode current collector is 1.0 to 5.3. 【0013】 Figure 1 is a partially cutaway perspective view schematically showing an example of the configuration of a lithium ion battery as a single cell. Figure 2 is an enlarged cross-sectional view of the single cell shown in Figure 1. 【0014】 A lithium-ion battery cell 1 is constructed by stacking a positive electrode 2, which has a positive electrode active material layer 5 formed on the surface of a roughly rectangular flat positive electrode current collector 7, and a negative electrode 3, which has a negative electrode active material layer 6 formed on the surface of a similarly roughly rectangular flat negative electrode current collector 9, with a roughly flat separator 4 in between. The entire cell is formed in a roughly rectangular flat shape. These positive and negative electrodes function as the positive and negative electrodes of a lithium-ion battery. In other words, a stacked unit consisting of a set of positive electrode current collectors, positive electrode active material layer, separator, negative electrode active material layer, and negative electrode current collector, stacked in sequence, is the unit that functions as a single cell. 【0015】 In addition to the stacked units described above, the single cell 1 has an annular frame member 8 positioned between the positive electrode current collector 7 and the negative electrode current collector 9, and around the positive electrode active material layer 5 and the negative electrode active material layer 6. The frame member 8 fixes the peripheral edge of the separator 4 and seals the positive electrode active material layer 5, the separator 4, and the negative electrode active material layer 6. The frame members 8 are assembled for the positive electrode 2 and the negative electrode 3 during the manufacturing process and then joined together. The frame member in contact with the positive electrode current collector 7 is the positive electrode frame member 8a, and the frame member in contact with the negative electrode current collector 9 is the negative electrode frame member 8b. 【0016】 In a single cell 1, the ratio (electrode thickness / frame thickness) between the electrode thickness (indicated by the double arrow T1 in Figure 2), which is the sum of the thicknesses of the positive electrode current collector 7, positive electrode active material layer 5, separator 4, negative electrode active material layer 6, and negative electrode current collector 9, and the frame thickness (indicated by the double arrow T2 in Figure 2), which is the sum of the thicknesses of the positive electrode current collector 7, frame member 8, separator 4, and negative electrode current collector 9, is between 1.0 and 5.3. 【0017】 By setting the electrode thickness / frame thickness to 1.0 to 5.3 mm, wear on the current collector can be suppressed, and a single cell can be made that does not leak electrolyte. This effect will be explained by referring to several configurations with different electrode thickness / frame thicknesses. The single cell shown in Figure 2 is an example where the electrode thickness / frame thickness is 1.0 (T1=T2). FIG. 3, FIG. 4, and FIG. 5 are cross-sectional views schematically showing examples of single cells with different electrode part thicknesses / frame part thicknesses. The single cell shown in FIG. 3 is an example where the electrode part thickness / frame part thickness exceeds 1.0 and is 5.3 or less (1.0 < T1 / T2 ≤ 5.3). The single cell shown in FIG. 4 is an example where the electrode part thickness / frame part thickness exceeds 5.3 (T1 / T2 > 5.3). The single cell shown in FIG. 5 is an example where the electrode part thickness / frame part thickness is less than 1.0 (T1 / T2 < 1.0). 【0018】 The single cell 22 shown in FIG. 4 is an example where the electrode part thickness is considerably thicker than the frame part thickness. In such an example, when stacking the single cells, pressure is applied to the inner edge of the frame part (the part indicated by X in FIG. 4), and the current concentrates. Therefore, the current collector is worn out at this part, and electrolyte leakage is likely to occur. Even in the single cell 21 shown in FIG. 3, pressure is applied to the inner edge of the frame part when stacking the single cells, but the degree of this pressure is smaller than that of the single cell 22 shown in FIG. 4. Therefore, it does not reach the wear of the current collector, and electrolyte leakage does not occur. In the single cell of the present invention, in order to prevent the wear of the current collector when stacking the single cells, the value of the electrode part thickness / frame part thickness is set to 5.3 or less. 【0019】 The single cell 23 shown in FIG. 5 is an example where the electrode part thickness is thinner than the frame part thickness. In such an example, when stacking the single cells, only the frame parts contact each other, and the electrode parts do not contact each other. Therefore, it cannot be made into a stacked battery. 【0020】 FIG. 6 is a top view of the single cell shown in FIG. 1. FIG. 6 shows the positions of the frame part and the electrode part when the single cell is viewed from above. The electrode part 10 is located inside the single cell 1, and the frame part 11 is located around the electrode part 10. In the single cell of the present invention, the width of the frame member constituting the frame part (the width indicated by double-headed arrow W in FIG. 6) is 3 to 15 mm, and the ratio of the top view area of the frame part (the area indicated by area S1 in FIG. 6) to the inner area of the frame part surrounded by the frame part (the area indicated by area S2 in FIG. 6) (frame part top view area S1 / frame part inner area S2) is preferably 0.03 to 0.20. Meeting these conditions prevents changes in the shape of individual cells during stacking. In Figure 6, the dimensions of the frame members are indicated by the double-headed arrow MD for the vertical length and the double-headed arrow TD for the horizontal length. 【0021】 Furthermore, the dimensional relationship between the frame and electrode portions shown above must be satisfied for both the positive electrode using the positive electrode frame member and the negative electrode using the negative electrode frame member. By satisfying the above relationship for both the positive and negative electrodes, it is possible to effectively prevent changes in the shape of the single cell during stacking. If the width of the frame members differs depending on the section of the frame (the side that makes up the frame), the width of the frame member with the shorter width shall be used as the representative value. 【0022】 In the drawings of this application, the internal frame area of ​​the positive electrode and the internal frame area of ​​the negative electrode are depicted as being the same; however, the internal frame areas of the positive electrode and the negative electrode do not necessarily have to be the same. The relationship between the internal frame areas of the positive and negative electrodes in each drawing is merely an example. In the embodiment shown below, the internal area of ​​the negative electrode frame is made slightly larger than the internal area of ​​the positive electrode frame. The internal surface area of ​​the positive electrode frame may be larger than the internal surface area of ​​the negative electrode frame. 【0023】 The following describes preferred embodiments of each component that make up a single cell. First, let's explain the individual elements that make up the stacking unit of a single cell. In the single cell of the present invention, it is preferable that the positive electrode active material layer and / or negative electrode active material layer include coated electrode active material particles in which at least a portion of the surface of the electrode active material particles is covered with a coating layer, and that the coated electrode active material particles are non-bound. When the positive electrode active material layer and / or the negative electrode active material layer is an unbound body of coated electrode active material particles and is flexible under pressure, the coated electrode active material particles can flow according to the pressure of the pressing. Therefore, unevenness will not be formed on the surface of the single cell. When there is no unevenness on the surface of the single cell, the loss of the current collector is more suppressed, and the effect of the single cell of the present invention is more exerted. In the description of the positive electrode active material layer and the negative electrode active material layer, the above aspect will be described. 【0024】 The positive electrode active material layer contains positive electrode active material particles. Examples of the positive electrode active material particles include composite oxides of lithium and transition metals {composite oxides with one transition metal (such as LiCoO2, LiNiO2, LiAlMnO4, LiMnO2, and LiMn2O4), composite oxides with two transition metal elements (for example, LiFeMnO4, LiNi 1-x Co x O2, LiMn 1-y Co y O2, LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O2 and LiNi 0.8 Co 0.15 Al 0.05 O2) and composite oxides with three or more metal elements [for example, LiM a M’ b M’’ c O2 (M, M’, and M’’ are different transition metal elements respectively, and satisfy a + b + c = 1. For example, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2) etc.] etc., lithium-containing transition metal phosphates (such as LiFePO4, LiCoPO4, LiMnPO4, and LiNiPO4), transition metal oxides (such as MnO2 and V2O5), transition metal sulfides (such as MoS2 and TiS2), and conductive polymers (such as polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole) etc. may be mentioned, and two or more kinds may be used in combination. Furthermore, lithium-containing transition metal phosphates may also be those in which some of the transition metal sites are substituted with other transition metals. 【0025】 The positive electrode active material particles are preferably coated positive electrode active material particles that are coated with a coating layer. The coating layer is a layer consisting of a conductive additive and a polymer compound. When the positive electrode active material particles are covered with a coating layer, the volume change of the electrode is mitigated, and the expansion of the electrode can be suppressed. 【0026】 Examples of conductive additives include metal-based conductive additives [aluminum, stainless steel (SUS), silver, gold, copper, and titanium, etc.], carbon-based conductive additives [graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, and thermal lamp black, etc.)], and mixtures thereof. These conductive additives may be used individually or in combination of two or more. They may also be used as alloys or metal oxides. In particular, from the viewpoint of electrical stability, aluminum, stainless steel, silver, gold, copper, titanium, carbon-based conductive additives, and mixtures thereof are more preferred, even more preferably silver, gold, aluminum, stainless steel, and carbon-based conductive additives, and especially preferably carbon-based conductive additives. Furthermore, these conductive additives may be made by coating a particulate ceramic material or resin material with a conductive material [preferably a metallic conductive additive from the above-mentioned conductive additives] by plating or the like. 【0027】 The shape (form) of the conductive additive is not limited to particle form, but may also be in a form other than particle form, such as carbon nanofibers or carbon nanotubes, which are already in practical use as so-called filler-type conductive additives. 【0028】 The ratio of polymer compound to conductive additive is not particularly limited, but from the viewpoint of the internal resistance of the battery, the weight ratio of polymer compound (resin solids weight):conductive additive is preferably 1:0.01 to 1:50, and more preferably 1:0.2 to 1:3.0. 【0029】 As for polymer compounds, those described in Japanese Patent Publication No. 2017-054703 as resins for coating non-aqueous secondary battery active materials can be suitably used. 【0030】 Furthermore, the positive electrode active material layer may contain conductive additives other than those included in the coated positive electrode active material. As the conductive additive, one similar to the conductive additive contained in the coated positive electrode active material described above can be suitably used. 【0031】 The coating layer may further contain ceramic particles. Examples of ceramic particles include metal carbide particles, metal oxide particles, and glass ceramic particles. 【0032】 Examples of metal carbide particles include silicon carbide (SiC), tungsten carbide (WC), molybdenum carbide (Mo2C), titanium carbide (TiC), tantalum carbide (TaC), niobium carbide (NbC), vanadium carbide (VC), and zirconium carbide (ZrC). 【0033】 Examples of metal oxide particles include zinc oxide (ZnO), aluminum oxide (Al2O3), silicon dioxide (SiO2), tin oxide (SnO2), titania (TiO2), zirconia (ZrO2), indium oxide (In2O3), Li2B4O7, and Li4Ti5O. 12Examples include perovskite-type oxide particles represented as Li2Ti2O5, LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li3PO4, Li2MoO4, Li3BO3, LiBO2, Li2CO3, Li2SiO3, and ABO3 (where A is at least one selected from the group consisting of Ca, Sr, Ba, La, Pr, and Y, and B is at least one selected from the group consisting of Ni, Ti, V, Cr, Mn, Fe, Co, Mo, Ru, Rh, Pd, and Re). As metal oxide particles, zinc oxide (ZnO), aluminum oxide (Al2O3), silicon dioxide (SiO2), and lithium tetraborate (Li2B4O7) are preferred from the viewpoint of effectively suppressing side reactions that occur between the electrolyte and the coated positive electrode active material particles. 【0034】 As for the ceramic particles, glass ceramic particles are preferable from the viewpoint of effectively suppressing side reactions that occur between the electrolyte and the coated positive electrode active material particles. These may be used individually or in combination of two or more types. 【0035】 The glass ceramic particles are preferably lithium-containing phosphate compounds having a rhombohedral crystal system, and their chemical formula is Li x M"2P3O 12 It can be expressed as (X = 1 to 1.7). Here, M'' is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Cr, Ca, Mg, Sr, Y, Sc, Sn, La, Ge, Nb, and Al. Furthermore, some of the P may be substituted with Si or B, and some of the O may be substituted with F, Cl, etc. For example, Li 1.15 Ti 1.85 Al 0.15 Si 0.05 P 2.95 O 12 Li 1.2 Ti 1.8 Al 0.1 Ge 0.1 Si 0.05 P 2.95 O 12 The following can be used. Furthermore, materials of different compositions may be mixed or compounded, and the surface may be coated with a glass electrolyte or the like. Alternatively, it is preferable to use glass ceramic particles that precipitate a crystalline phase of a lithium-containing phosphate compound having a NASICON-type structure by heat treatment. Examples of glass electrolytes include the glass electrolyte described in Japanese Patent Publication No. 2019-96478. 【0036】 Here, it is preferable that the proportion of Li2O in the glass ceramic particles is 8% by mass or less in terms of oxide. Even if it is not a NASICON-type structure, it is composed of Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, and F, and has liSICON-type, perovskite-type, β-Fe2(SO4)3-type, and Li3In2(PO4)3-type crystal structures, and Li ions can be released at room temperature in a quantity of 1 × 10⁻¹⁶. -5 A solid electrolyte with conductivity of S / cm or higher may also be used. 【0037】 The ceramic particles described above may be used individually or in combination of two or more types. 【0038】 The volume-average particle diameter of the ceramic particles is preferably 1 to 1000 nm, more preferably 1 to 500 nm, and even more preferably 1 to 150 nm, from the viewpoint of energy density and electrical resistance. In this specification, volume-average particle diameter refers to the particle size at 50% of the integrated value in the particle size distribution determined by the microtrac method (laser diffraction / scattering method) (Dv50). The microtrac method is a method for determining the particle size distribution using scattered light obtained by irradiating particles with laser light. For measuring the volume-average particle diameter, a microtrac manufactured by Nikkiso Co., Ltd. or similar can be used. 【0039】 The weight percentage of ceramic particles is preferably 0.5 to 5.0% by weight, based on the weight of the coated positive electrode active material particles. By including ceramic particles within the above range, side reactions occurring between the electrolyte and the coated positive electrode active material particles can be effectively suppressed. The weight percentage of ceramic particles is more preferably 2.0 to 4.0% by weight, based on the weight of the coated positive electrode active material particles. 【0040】 The positive electrode active material layer is preferably a non-binding body that contains positive electrode active material but does not contain a binder that binds the positive electrode active material together. Here, "non-bound" means that the positive electrode active materials are not bonded to each other, while "bonded" means that the positive electrode active materials are irreversibly fixed to each other. 【0041】 The positive electrode active material layer may contain an adhesive resin. Suitable adhesive resins include, for example, a resin for coating non-aqueous secondary battery active materials described in Japanese Patent Publication No. 2017-054703, which is prepared by mixing a small amount of organic solvent with the resin to adjust its glass transition temperature to below room temperature, and an adhesive described in Japanese Patent Publication No. 10-255805. Adhesive resins, in this context, refer to resins that retain their adhesive properties (the ability to bond with slight pressure without the use of water, solvents, or heat) even after drying by volatilizing the solvent components, without solidifying. On the other hand, solution-drying electrode binders used as binders refer to materials that dry and solidify by volatilizing the solvent components, thereby firmly bonding and fixing the active materials together. Therefore, solution-drying electrode binders (binding agents) and adhesive resins are different materials. 【0042】 The thickness of the positive electrode active material layer is not particularly limited, but from the viewpoint of battery performance, it is preferably 100 to 500 μm, and more preferably 150 to 450 μm. 【0043】 The negative electrode active material layer contains negative electrode active material particles. As negative electrode active material particles, known negative electrode active materials for lithium-ion batteries can be used, including carbon-based materials [graphite, non-graphitizable carbon, amorphous carbon, resin-fired bodies (e.g., phenolic resin and furan resin, etc., that have been fired and carbonized), cokes (e.g., pitch coke, needle coke and petroleum coke, etc.) and carbon fibers, etc.], silicon-based materials [silicon, silicon oxide (SiOx), silicon-carbon composites (carbon particles with the surface coated with silicon and / or silicon carbide, silicon particles or silicon oxide particles with the surface coated with carbon and / or silicon carbide, and silicon carbide, etc.)], and Examples include silicon alloys (silicon-aluminum alloys, silicon-lithium alloys, silicon-nickel alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys, and silicon-tin alloys, etc.), conductive polymers (e.g., polyacetylene and polypyrrole), metals (tin, aluminum, zirconium, and titanium, etc.), metal oxides (titanium oxide and lithium-titanium oxide, etc.), and metal alloys (e.g., lithium-tin alloys, lithium-aluminum alloys, and lithium-aluminum-manganese alloys, etc.), as well as mixtures of these with carbon-based materials. 【0044】 Furthermore, the negative electrode active material particles may be coated negative electrode active material particles coated with a coating layer similar to that of the coated positive electrode active material particles described above. As the conductive additives, polymer compounds, and ceramic particles constituting the coating layer, the same conductive additives, polymer compounds, and ceramic particles as those described above for the coated positive electrode active material particles can be suitably used. 【0045】 Furthermore, the negative electrode active material layer may contain conductive additives other than those contained in the coated negative electrode active material particles. Suitable conductive additives include those similar to those contained in the coated positive electrode active material particles described above. 【0046】 The negative electrode active material layer is preferably a non-binding material that does not contain a binder to bond the negative electrode active materials together, similar to the positive electrode active material layer. Furthermore, like the positive electrode active material layer, it may contain an adhesive resin. 【0047】 The thickness of the negative electrode active material layer is not particularly limited, but from the viewpoint of battery performance, it is preferably 100 to 550 μm, preferably 100 to 500 μm, and preferably 220 to 550 μm. 【0048】 The thickness of the positive electrode active material layer and the negative electrode active material layer may be the same or different, but the thickness of the negative electrode active material layer may be greater than the thickness of the positive electrode active material layer. 【0049】 Materials that constitute the positive electrode current collector and the negative electrode current collector (hereinafter collectively referred to simply as current collectors) include metallic materials such as copper, aluminum, titanium, stainless steel, nickel and their alloys, as well as calcined carbon, conductive polymer materials, conductive glass, and the like. Of these materials, aluminum is preferred as the positive electrode current collector and copper is preferred as the negative electrode current collector, from the viewpoint of weight reduction, corrosion resistance, and high conductivity. 【0050】 Furthermore, the current collector is preferably a resin current collector made of a conductive polymer material. The shape of the current collector is not particularly limited and may be a sheet-like current collector made of the above material, or a deposited layer made of fine particles composed of the above material. The thickness of the current collector is not particularly limited, but it is preferably 50 to 500 μm for both the positive electrode current collector and the negative electrode current collector. 【0051】 As the conductive polymer material constituting the resin current collector, for example, a conductive polymer or a resin to which a conductive agent is added as needed can be used. As the conductive agent constituting the conductive polymer material, the same conductive additive as that contained in the coated positive electrode active material described above can be suitably used. 【0052】 Examples of resins that constitute conductive polymer materials include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyethernitrile (PEN), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resins, silicone resins, or mixtures thereof. From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), and polycycloolefin (PCO) are preferred, and more preferably polyethylene (PE), polypropylene (PP), and polymethylpentene (PMP). 【0053】 Examples of separators include known separators for lithium-ion batteries such as porous films made of polyethylene or polypropylene, laminated films of porous polyethylene film and porous polypropylene, nonwoven fabrics made of synthetic fibers (polyester fibers and aramid fibers, etc.) or glass fibers, and those on which ceramic fine particles such as silica, alumina, and titania are attached to the surface. 【0054】 The positive electrode active material layer and the negative electrode active material layer contain an electrolyte. As the electrolyte, a known electrolyte containing an electrolyte and a non-aqueous solvent, which is used in the manufacture of known lithium-ion batteries, can be used. 【0055】 As the electrolyte, electrolytes used in known electrolytes can be used, such as lithium salts of inorganic anions such as LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, and LiN(FSO2)2, and lithium salts of organic anions such as LiN(CF3SO2)2, LiN(C2F5SO2)2, and LiC(CF3SO2)3. Of these, LiN(FSO2)2 is preferred from the viewpoint of battery output and charge / discharge cycle characteristics. 【0056】 As the solvent, any non-aqueous solvent used in known electrolytes can be used. For example, lactone compounds, cyclic or linear carbonate esters, linear carboxylic acid esters, cyclic or linear ethers, phosphate esters, nitrile compounds, amide compounds, sulfones, sulfolanes, and mixtures thereof can be used. 【0057】 Next, we will explain the frame members. The material constituting the frame member is not particularly limited as long as it is durable against the electrolyte, but polymer materials are preferred. Specifically, it is preferable that it consists of one or more materials selected from the group consisting of ethylene-vinyl acetate copolymer, maleic anhydride-modified polyethylene, and acid-modified polypropylene. 【0058】 Furthermore, it is preferable that the surface of the frame member that contacts the positive electrode current collector or the negative electrode current collector is made of one or more materials selected from the group consisting of ethylene-vinyl acetate copolymer, maleic anhydride-modified polyethylene, and acid-modified polypropylene. It is preferable that the surface of the frame member that contacts the positive electrode current collector or the negative electrode current collector is made of such a material because it improves the adhesion between the frame member and the current collector. 【0059】 The frame member consists of a positive electrode frame member and a negative electrode frame member. The positive electrode frame member and the negative electrode frame member may be made of different materials, or they may be made of the same material. The thickness of the positive electrode frame member and the negative electrode frame member is preferably 100 to 500 μm, respectively. Furthermore, the dimensions of the positive electrode frame member and the negative electrode frame member, such as thickness and width, may be the same or different. When the thicknesses of the positive electrode frame member and the negative electrode frame member are different, it is preferable that the thickness of the negative electrode frame member is greater than the thickness of the positive electrode frame member. 【0060】 The method for manufacturing a single cell of the present invention is not particularly limited, but it can be manufactured by separately fabricating a positive electrode and a negative electrode, stacking them with a separator in between, and sealing the surrounding area. For example, the following method can be used. [1] Fabrication of the positive electrode A positive electrode frame member is placed on the positive electrode current collector, and a positive electrode active material composition, which will form the positive electrode active material layer, is applied to the internal space of the positive electrode frame member. At this time, the amount of positive electrode active material composition applied is adjusted so that the thickness of the positive electrode active material layer is a predetermined thickness. In addition, an electrolyte is poured into the positive electrode active material layer. [2] Fabrication of the negative electrode A negative electrode frame member is placed on the negative electrode current collector, and a negative electrode active material composition, which will form the negative electrode active material layer, is applied to the frame portion of the negative electrode frame member. At this time, the amount of negative electrode active material composition applied is adjusted so that the thickness of the negative electrode active material layer is a predetermined thickness. In addition, an electrolyte is poured into the negative electrode active material layer. [3] Making a single cell A separator is placed between the positive electrode active material layer and the negative electrode active material layer, and the positive and negative electrodes are stacked so that the positive electrode active material layer and the negative electrode active material layer face each other with the separator in between. The overlapping portion of the positive electrode frame member and the negative electrode frame member is heated and pressurized, and the area around the stacked unit (electrode portion) is heat-sealed to seal the stacked unit. Heat sealing causes the positive electrode frame member and the negative electrode frame member to become an integrated frame member. A single cell can be manufactured through the process described above. 【0061】 The single cells of the present invention can be used as a battery module by stacking them. A battery module formed by stacking the single cells of the present invention is the battery module of the present invention. Figure 7 is a schematic cross-sectional view showing an example of a battery module. Figure 7 shows a battery module 101 in which four single cells 21, as shown in Figure 3, are stacked. In the battery module 101, the upper surfaces of the negative electrode current collectors 9 and the lower surfaces of the positive electrode current collectors 7 of adjacent single cells 21 are stacked in series, and the four stacked single cells 21 are housed in the container 120. 【0062】 A positive electrode lead-out section 107 is provided on the lower surface of the container 120, and a negative electrode lead-out section 109 is provided on the upper surface of the container 120. The positive electrode lead-out section 107 is electrically connected to the positive electrode current collector 7 of the lowest cell 21, and the negative electrode lead-out section 109 is electrically connected to the negative electrode current collector 9 of the uppermost cell 21. 【0063】 In this way, by stacking multiple single cells to form a battery module, it is possible to use a module with improved battery capacity and voltage. The single cells of the present invention suppress wear of the current collector due to stacking and do not leak electrolyte, thus providing a highly reliable battery module. [Examples] 【0064】 The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples unless it deviates from the spirit of the invention. Unless otherwise specified, parts refer to parts by weight, and % refers to % by weight. 【0065】 [Preparation of polymer compounds for coating] 150 parts of DMF were placed in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel, and nitrogen gas inlet tube, and the temperature was raised to 75°C. Next, a monomer composition containing 91 parts acrylic acid, 9 parts methyl methacrylate, and 50 parts DMF, along with an initiator solution containing 0.3 parts 2,2'-azobis(2,4-dimethylvaleronitrile) and 0.8 parts 2,2'-azobis(2-methylbutyronitrile) dissolved in 30 parts DMF, were continuously added dropwise over 2 hours using a dropping funnel while blowing nitrogen into the four-necked flask under stirring to carry out radical polymerization. After the dropwise addition was complete, the reaction was continued at 75°C for 3 hours. Next, the temperature was raised to 80°C and the reaction was continued for 3 hours to obtain a copolymer solution with a resin concentration of 30%. The obtained copolymer solution was transferred to a Teflon® vat and dried under reduced pressure at 150°C and 0.01 MPa for 3 hours, and the DMF was removed by distillation to obtain the copolymer. This copolymer was coarsely ground with a hammer, and then further ground in a mortar to obtain a powdered polymer compound for coating. 【0066】 [Preparation of electrolyte solution] An electrolyte was prepared by dissolving LiFSI (LiN(FSO2)2) at a ratio of 2.0 mol / L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (EC:PC volume ratio of 3:7). 【0067】 [Manufacturing of resin current collectors] A resin mixture was obtained by melt-kneading 70 parts of polypropylene [product name "Sun Allomer PL500A", manufactured by Sun Allomer Co., Ltd.], 25 parts of carbon nanotubes [product name "FloTube9000", manufactured by CNano], and 5 parts of dispersant [product name "Yumex 1001", manufactured by Sanyo Chemical Industries, Ltd.] in a twin-screw extruder at 200°C and 200 rpm. The obtained resin mixture was passed through a T-die extrusion film molding machine and stretched and rolled to obtain a conductive film for resin current collectors with a thickness of 50 μm. Next, the obtained conductive film for resin current collectors was cut to 400 mm x 500 mm, and nickel deposition was applied to one side to obtain resin current collectors. 【0068】 [Fabrication of coated negative electrode active material particles] One part of the coating polymer compound was dissolved in three parts of DMF to obtain a coating polymer compound solution. 76 parts of negative electrode active material particles (hard carbon powder, volume average particle size 25 μm) were placed in a universal mixer high-speed mixer FS25 [(manufactured by Earth Technica Co., Ltd.)], and while stirring at room temperature and 720 rpm, 9 parts of coating polymer compound solution were added dropwise over 2 minutes, and the mixture was stirred for a further 5 minutes. Next, while stirred, 9 parts of acetylene black [Denka Black® manufactured by Denka Co., Ltd.], 2 parts of carbon nanofiber [manufactured by Teijin Limited], and glass ceramic particles (product name "Lithium Ion Conductive Glass Ceramics LICGC") are added. TM PW-01 (1 μm) [manufactured by Ohara Co., Ltd.] (volume average particle size 1000 nm) was added in four portions over 2 minutes, and stirring was continued for 30 minutes. Subsequently, the pressure was reduced to 0.01 MPa while maintaining stirring, and then the temperature was raised to 140°C while maintaining stirring and reduced pressure. The stirring, reduced pressure, and temperature were maintained for 8 hours to remove volatile components by distillation. The obtained powder was classified using a sieve with a mesh size of 200 μm to obtain coated negative electrode active material particles. 【0069】 [Fabrication of coated cathode active material particles] One part of the coating polymer compound was dissolved in three parts of DMF to obtain a coating polymer compound solution. Positive electrode active material particles (LiNi 0.8 Co 0.15 Al 0.05 84 parts of O2 powder (volume average particle size 4 μm) were placed in a universal mixer high-speed mixer FS25 [(manufactured by Earth Technica Co., Ltd.)], and while stirring at room temperature and 720 rpm, 9 parts of the coating polymer compound solution were added dropwise over 2 minutes, and the mixture was stirred for a further 5 minutes. Next, while stirred, 3 parts of acetylene black [Denka Black (registered trademark) manufactured by Denka Co., Ltd.] and glass ceramic particles [product name: Lithium-ion conductive glass ceramics LICGC] are added. TM [PW-01 (1μm), manufactured by Ohara Corporation] was added in four portions over a period of 2 minutes, and stirring was continued for 30 minutes. Subsequently, the pressure was reduced to 0.01 MPa while maintaining stirring, and then the temperature was raised to 140°C while maintaining stirring and reduced pressure. The stirring, reduced pressure, and temperature were maintained for 8 hours to remove volatile components by distillation. The obtained powder was classified using a sieve with a mesh size of 200 μm to obtain coated cathode active material particles. 【0070】 (Manufacturing Examples 1-4) [Fabrication of negative electrode frame component] A negative electrode frame component was prepared by molding polyolefin resin into a ring shape. The width, MD length, TD length, top view area of ​​the frame, and internal area of ​​the frame are as shown in Table 1. The locations indicated by these dimensions are as shown in Figure 6. 【0071】 [Table 1] 【0072】 (Manufacturing examples 5-8) [Fabrication of positive electrode frame component] A positive electrode frame member was prepared by molding polyolefin resin into a ring shape. The width, MD length, TD length, top view area of ​​the frame section, and internal area of ​​the frame section are as shown in Table 2. The locations indicated by these dimensions are as shown in Figure 6. 【0073】 [Table 2] 【0074】 Note that Table 3 shows frame members with the same manufacturing example number but different thicknesses. Frame members with the same manufacturing example number have the same width, MD length, TD length, top view area of ​​the frame, and internal area of ​​the frame; they are shown as frame members with the same manufacturing example number even if their thicknesses are different. 【0075】 (Examples 1-6, Comparative Examples 1-4) [Fabrication of the negative electrode] 42 parts of electrolyte and 4.2 parts of carbon fiber [Donacarbo Milled S-243 manufactured by Osaka Gas Chemical Co., Ltd.: average fiber length 500 μm, average fiber diameter 13 μm: electrical conductivity 200 mS / cm] were mixed at 2000 rpm for 5 minutes using a planetary stirring type mixing and kneading device {Awatori Rentaro [manufactured by Shinky Co., Ltd.]}. Subsequently, 30 parts of the electrolyte and 206 parts of the coated negative electrode active material particles were added, and the mixture was further mixed at 2000 rpm for 2 minutes using the Awatori Rentaro. After adding another 20 parts of the electrolyte, the mixture was stirred at 2000 rpm for 1 minute using the Awatori Rentaro, and after adding another 2.3 parts of the electrolyte, the mixture was stirred at 2000 rpm for 2 minutes using the Awatori Rentaro to prepare the negative electrode active material composition. A negative electrode frame member according to one of the manufacturing examples 1 to 4 was placed on a resin current collector, and a negative electrode active material composition was applied to the frame portion of the negative electrode frame member. At this time, the amount of negative electrode active material composition applied was adjusted so that the thickness of the negative electrode active material layer was the predetermined thickness shown in Table 3. Furthermore, an electrolyte solution was injected into the negative electrode active material layer. 【0076】 [Fabrication of the positive electrode] 42 parts of electrolyte and 4.2 parts of carbon fiber [Donacarbo Milled S-243 manufactured by Osaka Gas Chemical Co., Ltd.: average fiber length 500 μm, average fiber diameter 13 μm: electrical conductivity 200 mS / cm] were mixed at 2000 rpm for 5 minutes using a planetary stirring type mixing and kneading device {Awatori Rentaro [manufactured by Shinky Co., Ltd.]}. Subsequently, 30 parts of the electrolyte and 206 parts of the coated positive electrode active material particles were added, and the mixture was further mixed at 2000 rpm for 2 minutes using the Awatori Rentaro. After adding another 20 parts of the electrolyte, the mixture was stirred at 2000 rpm for 1 minute using the Awatori Rentaro, and after adding another 2.3 parts of the electrolyte, the mixture was stirred at 2000 rpm for 2 minutes using the Awatori Rentaro to prepare the positive electrode active material composition. A positive electrode frame member according to one of the manufacturing examples 5 to 8 was placed on a resin current collector, and a positive electrode active material composition was applied to the frame portion of the positive electrode frame member. At this time, the amount of positive electrode active material composition applied was adjusted so that the thickness of the positive electrode active material layer was the predetermined thickness shown in Table 3. Furthermore, an electrolyte solution was injected into the positive electrode active material layer. 【0077】 [Manufacturing of lithium-ion batteries] The manufactured negative and positive electrodes were stacked together with a separator, and the overlapping portion of the positive and negative electrode frame members was heat-sealed by heating and pressurizing to produce lithium-ion batteries of Examples 1-6 and Comparative Examples 1-4. Cellguard #3501 was used as the separator. The configuration of the lithium-ion battery is shown in Table 3. 【0078】 [Lamination Testing] Eight lithium-ion batteries manufactured in Examples 1-6 and Comparative Examples 1-4 were stacked and pressure-laminated. After pressurized lamination, we observed whether electrolyte seepage occurred from the inner edge of the frame (indicated by X in Figure 4). Furthermore, we visually observed whether any shape changes occurred in the individual cells during stacking (i.e., whether the edges of the individual cells were curled upwards). The results are shown in Table 3. 【0079】 [Table 3] 【0080】 In each of the examples, no electrolyte leakage occurred. In comparative examples 1-3, electrolyte leakage occurred because the electrode thickness / frame thickness ratio was large. In Comparative Example 4, the value of electrode thickness / frame thickness was less than 1.0, and the electrodes did not come into contact with each other, so it could not be made into a stacked battery. Furthermore, in Example 3, where the ratio of the top surface area of ​​the frame to the inner area of ​​the frame was within the range of 0.03 to 0.20 for both the positive and negative electrodes, it was possible to prevent changes in the shape of the single cell during stacking. [Industrial applicability] 【0081】 The single cell of the present invention is particularly useful as a single cell used to provide a high-capacity lithium-ion battery when stacked, as it can suppress wear of the current collector and prevent electrolyte leakage when stacked. [Explanation of symbols] 【0082】 1, 21, 22, 23 single cells 2 Positive electrode 3 negative electrode 4 Separators 5 Cathode active material layer 6 Negative electrode active material layer 7 Positive electrode current collector 8 Frame members 8a Positive electrode frame member 8b Negative electrode frame member 9 Negative electrode current collector 10 Electrode section 11 Frame section 101 Battery Module 107 Positive electrode lead section 109 Negative electrode lead section 120 containers

Claims

[Claim 1] A stacked unit consisting of a set of positive electrode current collectors, positive electrode active material layer, separator, negative electrode active material layer and negative electrode current collector stacked in order, Between the positive electrode current collector and the negative electrode current collector, the periphery of the positive electrode active material layer and the negative electrode active material layer A single cell having an annular frame member arranged around it, The ratio of the electrode portion thickness (electrode portion thickness / frame portion thickness), which is the sum of the thicknesses of the positive electrode current collector, the positive electrode active material layer, the separator, the negative electrode active material layer, and the negative electrode current collector, to the frame portion thickness (electrode portion thickness / frame portion thickness), which is the sum of the thicknesses of the positive electrode current collector, the frame member, the separator, and the negative electrode current collector, is between 1.0 and 5.

3. A single cell in which the width of the frame member is 3 to 15 mm, and the ratio of the top view area of ​​the frame to the inner area enclosed by the frame (top view area of ​​frame / inner area of ​​frame) is 0.03 to 0.

20. [Claim 2] The single cell according to claim 1, wherein the frame member comprises a positive electrode frame member in contact with the positive electrode current collector and a negative electrode frame member in contact with the negative electrode current collector, and the thickness of each of the positive electrode frame member and the negative electrode frame member is 100 to 500 μm. [Claim 3] The single cell according to claim 1 or 2, wherein the surface of the frame member in contact with the positive electrode current collector or the negative electrode current collector is made of one or more materials selected from the group consisting of ethylene-vinyl acetate copolymer, maleic anhydride modified polyethylene, and acid-modified polypropylene. [Claim 4] The single cell according to any one of claims 1 to 3, wherein the positive electrode active material layer and / or the negative electrode active material layer includes coated electrode active material particles in which at least a portion of the surface of the electrode active material particles is covered with a coating layer, and the coated electrode active material particles are non-bound. [Claim 5] A battery module comprising stacking single cells according to any one of claims 1 to 4.

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