Separator and secondary battery

Abstract

Provide is a separator used for a secondary battery. The separator may be provided on a surface of the secondary battery that is in contact with a negative electrode, and may include a functional layer containing a nitrate. The porosity of the functional layer may be 5-95%, and the basis density of the nitrate is 0.01 g / cm3 to 3.0 g / cm3. The nitrate may include at least one selected from lithium nitrate, potassium nitrate, cesium nitrate, sodium nitrate, silver nitrate, calcium nitrate, zinc nitrate, copper nitrate, magnesium nitrate, indium nitrate, aluminum nitrate, ammonium nitrate, barium nitrate, and iron nitrate.

Description

Separators and secondary batteries

[0001] This invention relates to a separator and a secondary battery.

[0002] Patent Document 1 discloses a secondary battery comprising a separator having a functional resin layer coated with a lithium salt filler. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent No. 5853639 General disclosure

[0003] In a first embodiment of the present invention, a separator for use in a secondary battery is provided. The separator is provided on the surface in contact with the negative electrode of the secondary battery and may include a functional layer containing a nitrate. The porosity of the functional layer may be 5% or more and 95% or less, and the basis density of the nitrate is 0.01 g / cm³. ３ Above, 3.0g / cm ３ The following is acceptable:

[0004] In the above separator, the nitrate may include at least one selected from lithium nitrate, potassium nitrate, cesium nitrate, sodium nitrate, silver nitrate, calcium nitrate, zinc nitrate, copper nitrate, magnesium nitrate, indium nitrate, aluminum nitrate, ammonium nitrate, barium nitrate, and iron nitrate.

[0005] In any of the above-mentioned separators, the basis weight of the nitrate contained in the functional layer may be 0.1% or more and 100% or less of the mass of the functional layer.

[0006] In any of the above-mentioned separators, the thickness of the separator may be 0.1 μm or more and 100 μm or less.

[0007] In any of the above-mentioned separators, the thickness of the separator may be 0.2 μm or more and 50 μm or less.

[0008] In any of the above-mentioned separators, the thickness of the separator may be 0.5 μm or more and 20 μm or less.

[0009] In any of the above separators, the basis density of the nitrate is 0.1 g / cm³. ３ Above, 3.0g / cm ３The following is acceptable:

[0010] In any of the above separators, the basis density of the nitrate is 1.0 g / cm³. ３ Above, 3.0g / cm ３ The following is acceptable:

[0011] In any of the above separators, the surface density of the nitrate in the functional layer is 0.01 mg / cm². ２ Above, 100mg / cm ２ The following is acceptable:

[0012] In any of the above-mentioned separators, the porosity of the functional layer may be 20% or more and 85% or less.

[0013] In any of the above-mentioned separators, the porosity of the functional layer may be 35% or more and 75% or less.

[0014] In any of the above separators, the functional layer may contain an inorganic material whose mass is 0.1% or more and 80% or less of the mass of the functional layer. The inorganic material may contain at least one selected from alumina, boehmite, silica, and titania.

[0015] Any of the above separators may include a binder for supporting the nitrate on the separator. The mass of the binder may be 0.1% or more and 20% or less of the mass of the functional layer.

[0016] In any of the above separators, the binder may contain at least one selected from polyvinylidene fluoride (PVDF), acrylic latex, acrylic resin, polyacrylic acid, polyacrylic acid-styrene copolymer, styrene-butadiene rubber, polyvinyl alcohol, epoxy resin, sodium polyacrylate, polytetrafluoroethylene, polysiloxane, polyoxyethylene-methylpolysiloxane copolymer, polyimide, polyamide, polyamideimide, polyester, carboxymethylcellulose, cellulose derivatives, and polysulfone.

[0017] Any of the above separators may contain fibers for supporting the nitrate on the separator. The mass of the fibers may be 0.5% or more and 30% or less of the mass of the nitrate.

[0018] In any of the above separators, the fiber may be at least one selected from hollow fibers, nanofibers, porous polymer fibers, and cellulose fibers.

[0019] In any of the above-mentioned separators, a buffer layer containing an inorganic material and a binder may be provided on the surface in contact with the positive electrode of the secondary battery.

[0020] In a second aspect of the present invention, a secondary battery is provided comprising any of the above-mentioned separators, a negative electrode in contact with the functional layer, and a positive electrode disposed at a distance from the negative electrode.

[0021] In the above-described secondary battery, the functional layer may also be provided on the surface of the separator that is in contact with the positive electrode.

[0022] In any of the above secondary batteries, the negative electrode may be a lithium metal negative electrode, a graphite negative electrode, a silicon oxide negative electrode, or a silicon negative electrode.

[0023] It should be noted that the above summary of the invention does not enumerate all of its features. Furthermore, subcombinations of these features may also constitute an invention.

[0024] A schematic diagram of the internal structure of the battery 100 is shown. A schematic diagram of the positive electrode 120 is shown. A schematic diagram of the negative electrode 140 is shown. A schematic diagram of the separator 130 is shown. A schematic diagram of a modified separator 130 is shown. A schematic diagram of the electrode structure 610 is shown. A schematic diagram of the manufacturing method of the battery 100 is shown.

[0025] The present invention will be described below through embodiments, but these embodiments are not intended to limit the scope of the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0026] In this specification, when a numerical range is expressed as "A to B", this expression means A or more and B or less. Further, "substituted or unsubstituted" means "substituted with any substituent or not substituted with a substituent". The type of the above-mentioned substituent is not particularly limited unless otherwise mentioned in the specification. Also, the number of the above-mentioned substituents is not particularly limited unless otherwise mentioned in the specification.

[0027] (Outline of the storage battery 100) FIG. 1 schematically shows an example of the internal structure of the storage battery 100. FIG. 1 may be an example of a cross-sectional view of the storage battery 100. In this example, the details of the storage battery 100 are described by taking the case where the storage battery 100 is a rectangular secondary battery as an example.

[0028] In this example, the storage battery 100 stores electrical energy. Also, the storage battery 100 supplies the stored electrical energy to the outside. A power source can be produced by connecting a plurality of storage batteries 100 in series and / or in parallel.

[0029] The type of the storage battery 100 is not particularly limited, but the storage battery 100 may be an insertion-type storage battery or a reserve-type storage battery. The storage battery 100 may be a metal negative electrode battery using a metal as a negative electrode active material. Thereby, a storage battery 100 having a large energy density can be obtained. Examples of the metal negative electrode battery include an alkali metal negative electrode storage battery which is a secondary battery using an alkali metal as a negative electrode material, and a magnesium metal storage battery which is a secondary battery using magnesium metal (sometimes referred to as metallic magnesium) as a negative electrode material. Examples of the alkali metal negative electrode storage battery include a lithium metal storage battery which is a secondary battery using lithium metal (sometimes referred to as metallic lithium) as a negative electrode material.

[0030] The storage battery 100 may be a lithium ion storage battery using an inorganic material as a negative electrode active material. As the negative electrode active material, artificial or natural graphite, silicon oxide (SiO ｘ ) or silicon (Si) may be included.

[0031] (Outline of parts of the storage battery 100) In this example, the storage battery 100 includes an electrode structure 110. In this example, the electrode structure 110 includes a positive electrode 120, a separator 130, and a negative electrode 140. As shown in Figure 1, in this example, the electrode structure 110 includes a laminate in which at least the negative electrode 140, the first separator 130, the positive electrode 120, and the second separator 130 are stacked in this order.

[0032] In this example, the details of the electrode structure 110 will be described using the case where one of the outermost layers of the electrode structure 110 is a positive electrode 120 and the other of the outermost layers of the electrode structure 110 is a negative electrode 140 as an example. However, the structure of the electrode structure 110 is not limited to this example. The electrode structure 110 may have various structures in which the positive electrode 120 and the negative electrode 140 are arranged opposite each other via a separator 130. For example, in a modified example, both of the outermost layers of the electrode structure 110 may be positive electrodes 120, or both of the outermost layers of the electrode structure 110 may be negative electrodes 140.

[0033] In this example, a positive electrode tab 122 is provided at the end of the positive electrode 120. In this example, a negative electrode tab 142 is provided at the end of the negative electrode 140. In this example, the storage battery 100 comprises a non-aqueous electrolyte 150, a battery case 160, a positive electrode terminal 162, a negative electrode terminal 164, a positive electrode lead 172, and a negative electrode lead 174.

[0034] In this example, the electrode structure 110 has a structure in which a positive electrode 120 and a negative electrode 140 are alternately stacked with a separator 130 in between. The separator 130 may be made up of a single sheet that has been folded, or it may be made up of multiple sheets.

[0035] In the storage battery 100 according to this example, the positive electrode 120 and the negative electrode 140 are arranged such that the positive electrode active material of the positive electrode 120 and the negative electrode active material of the negative electrode 140 face each other with a separator 130 in between. The negative electrode 140 has the function of directly exchanging charge in conjunction with the reaction of the positive electrode active material, for example. In contrast, depending on the type of battery, a third type of electrode may be provided in addition to the positive and negative electrodes.

[0036] For example, depending on the type of lithium-ion battery, a lithium electrode having lithium metal foil may be provided separately from the negative electrode. The lithium-ion battery described above includes, for example, an electrode stacking unit with a stacked structure of positive electrode / first separator / negative electrode / first separator / positive electrode / second separator / lithium electrode. In this case, the positive electrode and the lithium electrode are arranged so that the current collector of the positive electrode and the lithium metal foil of the lithium electrode face each other via the second separator. On the other hand, the positive electrode and the negative electrode are arranged so that the positive electrode active material of the positive electrode and the negative electrode active material of the negative electrode face each other with a separator in between. In this respect, the lithium electrode and the negative electrode can be distinguished.

[0037] (Positive electrode) The positive electrode 120 is positioned away from the negative electrode 140. In this example, the positive electrode 120 is electrically connected to the positive electrode terminal 162 via a positive electrode tab 122 and a positive electrode lead 172. In this example, the positive electrode tab 122 is positioned to protrude from the positive electrode 120. Details of the positive electrode 120 and the positive electrode tab 122 will be described later.

[0038] (Separator) In this example, the separator 130 is positioned between the positive electrode 120 and the negative electrode 140, separating them. This prevents the positive electrode 120 and the negative electrode 140 from directly contacting each other and causing a short circuit. The separator 130 ensures ionic conductivity between the positive electrode 120 and the negative electrode 140, for example, by holding the non-aqueous electrolyte 150.

[0039] In this example, the separator 130 is provided with a functional layer 135 on the surface that contacts the negative electrode 140. Details of the functional layer 135 will be described later.

[0040] The separator 130 includes, for example, one or more polymer materials, one or more inorganic materials, and combinations thereof. Examples of materials for the separator 130 include cellulose, polyethylene terephthalate (PET), polyolefin, glass, and composites thereof. Examples of polyolefins include polyethylene, polypropylene, and ethylene-propylene copolymer.

[0041] Examples of the shape of the separator 130 include microporous films, nonwoven fabrics, and filters. The separator 130 may also be a laminate of these films or the like. The thickness of the separator 130 is not particularly limited, but is preferably 10 to 50 μm. The aperture ratio of the separator 130 is not particularly limited, but is preferably 30 to 70%.

[0042] The separator 130 may include multiple layers. At least two of the multiple layers may be layers with different materials, structures, and / or physical properties.

[0043] The separator 130 may include at least one layer of polyolefin film. The polyolefin film may be an unoriented film or an oriented film. The polyolefin film may be a porous oriented film. The oriented film may be a uniaxially oriented film or a biaxially oriented film.

[0044] The method for producing a porous polyolefin membrane that can be used as a separator 130 is not particularly limited, but dry and wet methods are examples of such methods. In the dry method, first, the resin material is heated, causing the resin material to melt. Next, the molten resin material is formed into a film. Then, the filmized resin is heat-treated, and after that, the resin is stretched under specific conditions. This produces a film-like resin with pores formed in it.

[0045] According to the wet process, first, a mixture of resin material and plasticizer is heated. This melts the mixture. The mixture may also contain inorganic fillers. Next, the molten mixture is formed into a film. Then, the film is stretched under specific conditions. After that, a process to extract the plasticizer and a washing process are carried out. This produces a film-like resin with pores formed on it.

[0046] (Functional layer) The functional layer 135 is a layer containing nitrate. In this example, the functional layer 135 is provided on the surface of the separator 130 that is in contact with the negative electrode 140. The functional layer 135 may be formed by coating the separator 130 with a slurry in which a metal salt, metal oxide, or polymer compound is dispersed in an organic solvent.

[0047] In this example, the basis density of nitrate in functional layer 135 is 0.01 g / cm³. ３ Above, 3.0g / cm ３ The following is the basis density of nitrates in functional layer 135: 0.1 g / cm³ ３ The above is acceptable, and 1.0 g / cm³ ３ That's all.

[0048] The basis density of nitrates in the functional layer 135 is the weight of nitrates per unit volume of the functional layer 135. ３ ) is the basis weight (g) of nitrate in the functional layer, and the volume (cm³) of the functional layer. ３ The amount of nitrate (g) can be calculated by dividing by the volume of nitrate contained in the functional layer (cm³). ３ ) and the literature value for nitrate density (g / cm³) ３ You can calculate it by multiplying by ).

[0049] In this example, the porosity of the functional layer 135 is 5% or more and 95% or less. The porosity of the functional layer 135 may be 20% or more and 35% or more. The porosity of the functional layer 135 may be 85% or less and 75% or less.

[0050] Porosity in the functional layer 135 refers to the void ratio of the material supported by the functional layer 135. In this example, the functional layer 135 is formed by coating the separator 130 with a coating solution in which nitrates, a binder, inorganic materials, a dispersant, etc., are dispersed in water or an organic solvent. At this time, not all of the material contained in the coating solution is supported on the functional layer 135. Therefore, the theoretical density of the functional layer 135 calculated by means of a calculation differs from the measured actual density of the functional layer 135. In this specification, the porosity of the functional layer 135 is calculated by dividing the measured density of the functional layer 135 by the theoretical density and subtracting this from 1.

[0051] The basis weight (g) of nitrate in the functional layer 135 may be 0.1% or more and 100% or less of the mass of the functional layer 135. The basis weight (g) of nitrate is the volume (cm³) of nitrate contained in the functional layer 135. ３ ) and the density of nitrates (g / cm³) ３ It was calculated by multiplying by the literature value of ).

[0052] The surface density of nitrates in functional layer 135 of this example (mg / cm²) ２ ) is 0.01 (mg / cm³) ２ ) or more, 100 (mg / cm ２ ) or less. Surface density of nitrate in functional layer 135 (mg / cm³) ２ ) is 0.1 (mg / cm³) ２ ) or more, and 0.2 (mg / cm³ ２ ) or more is acceptable. Surface density of nitrate in functional layer 135 (mg / cm³) ２ ) is 20 (mg / cm³). ２ ) may be less than or equal to 10 (mg / cm³). ２ It may be less than or equal to (mg / cm³). Surface density of nitrate ２ ) is calculated by dividing the weight (mg) of nitrates contained in the functional layer 135 by the bottom area (cm²) of the functional layer 135. ２ You can calculate it by dividing by ).

[0053] The nitrate contained in the functional layer 135 may be a nitrate of the carrier metal of the storage battery 100. The nitrate may be an alkali metal nitrate or an alkaline earth metal nitrate. The nitrate may be at least one selected from lithium nitrate, potassium nitrate, cesium nitrate, sodium nitrate, silver nitrate, calcium nitrate, zinc nitrate, copper nitrate, magnesium nitrate, indium nitrate, aluminum nitrate, ammonium nitrate, barium nitrate, and iron nitrate.

[0054] The functional layer 135 may contain an inorganic material in an amount of 0.1% or more and 80% or less of the mass of the functional layer 135. The inorganic material may be a metal oxide. The inorganic material may contain at least one selected from alumina, boehmite, silica, and titania. By including an inorganic material in the functional layer 135, the heat resistance of the functional layer 135 can be improved.

[0055] The functional layer 135 contains a binder for supporting nitrate on the separator 130. The mass of the binder contained in the functional layer 135 may be 0.1% or more and 20% or less of the mass of the functional layer 135. By including the binder in the functional layer 135, a flexible electrolytic film can be formed that follows the volume change of the negative electrode 140.

[0056] The binder only needs to be chemically stable in the storage battery 100, and its type is not particularly limited. A thermoplastic resin or a thermosetting resin may be used as the binder. The binder may contain at least one selected from polyvinylidene fluoride (PVDF), acrylic latex, acrylic resin, polyacrylic acid, polyacrylic acid-styrene copolymer, styrene-butadiene rubber, polyvinyl alcohol, epoxy resin, sodium polyacrylate, polytetrafluoroethylene, polysiloxane, polyoxyethylene-methylpolysiloxane copolymer, polyimide, polyamide, polyamideimide, polyester, carboxymethylcellulose, cellulose derivatives, and polysulfone.

[0057] The functional layer 135 contains fibers for supporting the nitrate on the separator 130. The mass of the fibers may be 0.5% or more and 30% or less of the mass of the nitrate to be supported.

[0058] The fiber has multiple fibers or bundles of fibers (these may be referred to as filaments). The multiple filaments form one or more voids that extend within the fiber. The fiber may be at least one selected from hollow fibers, nanofibers, porous polymer fibers, and cellulose fibers. The fiber may be a natural fiber, synthetic fiber, glass fiber, metal fiber, ceramic fiber, pulp, carbon fiber, etc.

[0059] (Negative electrode) In this example, the negative electrode 140 is electrically connected to the negative electrode terminal 164 via the negative electrode tab 142 and the negative electrode lead 174. In this example, the negative electrode tab 142 is positioned to protrude from the negative electrode 140.

[0060] If the storage battery 100 is a lithium metal battery using lithium metal as the negative electrode active material, lithium metal may dissolve and leach from the negative electrode 140. If the storage battery 100 is a lithium metal battery using lithium metal as the negative electrode active material, the electrode potential of the negative electrode 140 with respect to Li / Li+ may be 0.5V or less. The above electrode potential may be 0.2V or less, and preferably 0.1V or less. Details of the negative electrode 140 and the negative electrode tab 142 will be described later.

[0061] (Non-aqueous electrolyte) The non-aqueous electrolyte 150 forms an electrolytic film on the negative electrode 140 when the storage battery 100 is being charged. The non-aqueous electrolyte 150 enables ion conduction between the positive electrode active material and the negative electrode active material through the electrolyte contained in the non-aqueous electrolyte 150. A known organic electrolyte may be used as the non-aqueous electrolyte 150. The non-aqueous electrolyte 150 includes, for example, a metal salt as an electrolyte and a polar solvent. The polar solvent may be an organic solvent.

[0062] The metal salt contained in the non-aqueous electrolyte 150 may be a salt of the carrier metal of the storage battery 100. The carrier metal may be an alkali metal. Examples of metal salts include lithium salt, sodium salt, potassium salt, cesium salt, magnesium salt, calcium salt, aluminum salt, zinc salt, silver salt, indium salt, ammonium salt, barium salt, and iron salt. A single type of metal salt may be used, or a combination of multiple types of metal salts may be used.

[0063] The metal salt may include alkali metal salts or alkaline earth metal salts. The metal salt may include alkali metal or alkaline earth metal nitrates. The metal salt may be one or more selected from nitrates such as lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, magnesium nitrate, calcium nitrate, aluminum nitrate, zinc nitrate, silver nitrate, lead nitrate, indium nitrate or copper nitrate, at least one alkali metal salt selected from the group consisting of alkali metal fluoride salts, chloride salts, bromide salts, iodide salts, nitrates, nitrites, borates, fluoroborates, phosphates, fluorophosphates, sulfates or fluorosulfates, and at least one alkaline earth metal salt selected from the group consisting of alkaline earth metal fluoride salts, chloride salts, bromide salts, iodide salts, nitrates, nitrites, borates, fluoroborates, phosphates, fluorophosphates, sulfates or fluorosulfates.

[0064] The organic solvent contained in the non-aqueous electrolyte 150 is not limited in type, as long as it dissolves the metal salts mentioned above and is unlikely to cause side reactions such as decomposition within the voltage range used as a battery. A single type of organic solvent may be used as the organic solvent, or a combination of multiple organic solvents may be used.

[0065] The organic solvent is an ether-based or ester-based solvent that can be solvated with the metal salt described above. The organic solvent may be at least one selected from ethylene carbonate (EC), fluoroethylene carbonate (FEC), and dimethyl carbonate (DMC).

[0066] The electrolyte contained in the non-aqueous electrolyte 150 acts as a transport medium for ions involved in electrochemical reactions within the secondary battery. The electrolyte is lithium hexafluoride phosphate (LiPF). ６ ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiBF ４ LiClO ４ LiC (CF ３ SO ２ ) ３ LiCH (CF ３SO ２ ), ２ LiF, LiCl, LiBr, LiI, or Li ２ S, including at least one selected from the above. The electrolyte is LiB １２ F １２ LiAsF ６ LiFSO ３ Li ２ SiF ６ LiCF ３ CO ２ LiCH ３ CO ２ LiCF ３ SO ３ LiC ４ F ９ SO ３ LiCF ３ CF ２ SO ３ LiCF ３ (CF ２ ) ７ SO ３ LiCF ３ CF ２ (CF ３ ) ２ CO, Li(CF ３ SO ２ ) ２ CH, LiNO ３ LiN(CN) ２ LiN(FSO ２ ) ２ LiN(F ２ SO ２ ) ２ LiN(CF ３ SO ２ ) ２ LiN(C ２ F ５ SO ２ ) ２ LiP(CF ３ ) ６ LiPF(CF ３ ) ５ LiPF ２ (CF<00000,89>)<, ４ LiPF ３ (CF ３ ) ３ LiPF ４ (CF ３ )２ , LiPF ４ (C ２ F ５ ) ２ , LiPF ４ (CF ３ SO ２ ) ２ , LiPF ４ (C ２ F ５ SO ２ ) ２ , LiBF ２ C ２ O ４ , LiBO ４ O ８ , LiBF ２ (CF ３ ) ２ , LiBF ２ (C ２ F ５ ) ２ , LiBF ２ (CF ３ SO ２ ) ２ , LiBF ２ (C ２ F ５ SO ２ ) ２ , LiSbF ６ , LiAlO ４ , LiAlF ４ , LiSCN or LiAlCl ４ etc. may be included.

[0067] The non-aqueous electrolyte 150 may contain additional additives. Examples of additives include hydrofluoroethers (HFE). Hydrofluoroethers include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OTE), 3,3,4,4-tetrafluorotetrahydrofuran (FTHF), 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane (HFE-7300), hexafluoroisopropyl methyl ether, and methyl nonafluorobutyl It may contain at least one selected from ether, methyl 2,2,3,3,3-pentafluoropropyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, methyl 1,1,2,2-tetrafluoroethyl ether, or ethyl 1,1,2,2-tetrafluoroethyl ether.

[0068] (Housing) The battery case 160 houses the electrode structure 110 and the non-aqueous electrolyte 150. The electrode structure 110 and the non-aqueous electrolyte 150 may be sealed.

[0069] (An example of another embodiment) In this example, an example of a storage battery 100 has been described using the case where the storage battery 100 is a rectangular battery. However, the storage battery 100 is not limited to this example. In the modified example, the storage battery 100 may be a cylindrical battery, a laminated battery (sometimes called a pouch battery), or a coin cell battery.

[0070] In this example, an example of an electrode structure 110 was described, in which the electrode structure 110 has a laminated structure in which the positive electrode and negative electrode are alternately stacked with a separator in between. However, the electrode structure 110 is not limited to this example. In a modified example, the electrode structure 110 may have a wound type (sometimes referred to as a jelly roll type) in which the positive electrode, separator and negative electrode are stacked and wound into a roll.

[0071] (Electrochemical performance of the battery 100) The electrochemical performance of the battery 100 is influenced by the chemical reactions on the negative electrode 140 during charging and discharging of the battery 100. Specifically, it is desirable that an electrolytic film with good ion carrier conductivity and electrical conductivity be formed on the negative electrode 140 during charging and discharging of the battery 100.

[0072] Patent Document 1, listed in the prior art documents, discloses a separator having a base layer, on the side in contact with the negative electrode, a functional resin layer made of a material having a different through-hole diameter than the base layer, and a lithium salt filler being coated onto the functional resin layer. The present inventors conducted further tests on the disclosure of Patent Document 1 and confirmed that simply coating the surface of the separator in contact with the negative electrode does not improve the charge-discharge cycle life of the storage battery in some cases.

[0073] The inventors have found that when a functional layer 135 containing nitrate is placed on the surface where the separator 130 and the negative electrode 140 are in contact, the charge-discharge cycle life of the storage battery 100 is improved when both the basis density of nitrate in the functional layer 135 and the porosity of the functional layer 135 are within a predetermined range. In particular, they have found that the basis density of nitrate and the porosity can be adjusted by changing the composition of the coating liquid used to form the functional layer 135.

[0074] The inventors have found that the electrolyte within the functional layer 135 can be homogenized by adjusting the porosity of the functional layer 135. When the porosity of the functional layer 135 is high, the contact area between the functional layer 135 and the non-aqueous electrolyte increases. Conversely, when the porosity of the functional layer 135 is low, the contact area between the functional layer 135 and the non-aqueous electrolyte decreases.

[0075] The inventors have further discovered that, in addition to porosity, the basis density of nitrate in the functional layer 135 can be changed to adjust the dissolution rate of nitrate from the functional layer 135 into the electrolyte. This results in a property where the nitrate is released into the electrolyte more slowly than when nitrate alone is coated, i.e., sustained release properties are exhibited. In this way, the sustained release properties of the nitrate coated on the functional layer 135 suppress the rapid change in the concentration of carrier metal ions at the interface of the negative electrode 140 during the charge-discharge process. As a result, the resistance value at the interface of the negative electrode 140 can be kept constant, improving the charge-discharge cycle life of the storage battery 100.

[0076] Furthermore, Patent Document 1 does not mention the basis density and porosity of nitrates in the functional resin layer. Therefore, with the configuration of Patent Document 1, it is not possible to improve the charge-discharge cycle life of the storage battery 100 by adjusting the porosity and basis density of nitrates in the functional layer 135, as in this example.

[0077] (Positive electrode) Figure 2 schematically shows an example of a positive electrode 120. In this example, the positive electrode 120 comprises a positive electrode current collector 220 and a positive electrode active material layer 240. The positive electrode 120 may comprise a laminate in which the positive electrode current collector 220 and the positive electrode active material layer 240 are stacked in this order. In this example, the positive electrode current collector 220 has a first main surface 222, a second main surface 224, and a side surface 226 connecting the first main surface 222 and the second main surface 224.

[0078] In this example, for the purpose of simplifying the explanation, the details of the positive electrode 120 will be described using the example where the positive electrode active material layer 240 is arranged on one side of the positive electrode current collector 220. However, the positive electrode 120 is not limited to this example. In a modified example, the positive electrode active material layer 240 may be arranged on both sides of the positive electrode current collector 220.

[0079] In this example, one end of the positive electrode current collector 220 has a region where the positive electrode active material layer 240 is not formed. This region is used as the positive electrode tab 122. In a modified example, a conductive terminal member may be provided on at least a part of the positive electrode tab 122. The material of the terminal member is not particularly limited, but examples include nickel, iron, copper, and aluminum.

[0080] In this example, the positive electrode current collector 220 holds the positive electrode active material layer 240. The material of the positive electrode current collector 220 can be any chemically stable electron conductor in the storage battery 100, and its type is not particularly limited. Examples of materials for the positive electrode current collector 220 include nickel, copper, iron, aluminum, stainless steel, nickel, titanium, or alloys thereof. Examples of shapes for the positive electrode current collector 220 include foil, mesh, punched metal, expanded metal, etc. The thickness of the positive electrode current collector 220 is not particularly limited, but is preferably 5 to 200 μm. The thickness of the positive electrode current collector 220 may be 6 to 20 μm.

[0081] In this example, the positive electrode active material layer 240 is formed on at least one surface of the positive electrode current collector 220. The thickness of the positive electrode active material layer 240 may be 1 to 300 μm or 2 to 200 μm per side of the positive electrode current collector 220. The positive electrode active material layer 240 includes, for example, a positive electrode active material and a binder. The positive electrode active material layer 240 may also contain a conductive additive.

[0082] In one embodiment, the positive electrode active material layer 240 is formed by applying a paste containing the materials constituting the positive electrode active material layer 240 and an organic solvent to at least one surface of the positive electrode current collector 220, and then drying the paste. The type of organic solvent is not particularly limited, but examples of such organic solvents include N-methylpyrrolidone (NMP). In a modified example, the positive electrode active material layer 240 is formed by mixing the materials constituting the positive electrode active material layer 240, molding them into a sheet, and then pressing the sheet-like mixture onto at least one surface of the positive electrode current collector 220.

[0083] As the positive electrode active material, for example, a material that can insert and remove metal ions that act as charge carriers and has a higher potential than the negative electrode active material is used. For example, if the storage battery 100 is a lithium battery, insertion-type transition metal oxides such as lithium layered oxide systems, olivine systems, and spinel systems are used as the positive electrode active material. Examples of lithium batteries include lithium-ion batteries and lithium metal batteries.

[0084] A high-capacity conversion-type positive electrode active material may be used as the positive electrode active material. Examples of high-capacity conversion-type positive electrode active materials include sulfur, sulfur compounds, iron fluoride, and transition metal oxides. Conversion-type positive electrode active materials do not contain metals that act as charge carriers in their initial state. Therefore, when a positive electrode containing a conversion-type positive electrode active material is combined with a metal negative electrode, the energy density of the battery 100 is greatly improved.

[0085] In this example, the binder binds the materials constituting the positive electrode active material layer 240 (e.g., positive electrode active material, conductive additive, etc.) and maintains the electrode shape of the positive electrode 120. The binder only needs to be chemically stable in the storage battery 100, and its type is not particularly limited. A thermoplastic resin or a thermosetting resin may be used as the binder. Examples of binders include polyethylene, polypropylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, and styrene-butadiene rubber.

[0086] In this example, the conductive additive reduces the resistance of the positive electrode 120. The conductive additive can be any material that is chemically stable in the battery 100 and has the desired electronic conductivity, and its type is not particularly limited. Inorganic materials or organic materials may be used as the conductive additive. Carbon materials are examples of conductive additives. Examples of carbon materials include graphite, carbon black (e.g., acetylene black, Ketjenblack, etc.), coke, amorphous carbon, carbon fibers, carbon nanotubes, and graphene. These conductive additives may be used alone or in combination of two or more types.

[0087] (Negative Electrode) In the embodiment shown in Figure 3, the negative electrode 140 comprises, for example, a negative electrode current collector 320 and a negative electrode active material layer 340. The negative electrode 140 may comprise a laminate in which the negative electrode current collector 320 and the negative electrode active material layer 340 are stacked in this order. This separates the positive electrode active material layer 240 of the positive electrode 120 and the negative electrode active material layer 340 of the negative electrode 140 by at least a separator 130. As a result, an electrode structure 110 with excellent short-circuit resistance, chemical stability, and / or physical stability is obtained. The negative electrode 140 may have other layers between the negative electrode current collector 320 and the negative electrode active material layer 340.

[0088] In this example, for the purpose of simplifying the explanation, the details of the negative electrode 140 will be described using the example where the negative electrode active material layer 340 is arranged on one side of the negative electrode current collector 320. However, the negative electrode 140 is not limited to this example. In a modified example, the negative electrode active material layer 340 may be arranged on both sides of the negative electrode current collector 320. In this case, the negative electrode 140 is formed by stacking, for example, the negative electrode active material layer 340, the negative electrode current collector 320, and the negative electrode active material layer 340 in that order.

[0089] In this example, the negative electrode current collector 320 has a first main surface 322, a second main surface 324, and a side surface 326 connecting the first main surface 322 and the second main surface 324. In this example, the negative electrode active material layer 340 has a first main surface 342, a second main surface 344, and a side surface 346 connecting the first main surface 342 and the second main surface 344.

[0090] In this example, the main surface of each layer may be a surface substantially perpendicular to the thickness direction of the negative electrode 140. In each layer, one of the two main surfaces may be a smooth surface (sometimes called a shiny surface or S surface). The other of the two main surfaces may be a rough surface (sometimes called a matte surface or M surface). The side surface of each layer may be a surface that extends in the thickness direction of the negative electrode 140.

[0091] For the purpose of simplifying the explanation, in this example, an example of the negative electrode 140 is described using the case where the negative electrode current collector 320 and the negative electrode active material layer 340 have a rectangular plate shape or a rectangular prism shape. However, the shape of the negative electrode current collector 320 and the negative electrode active material layer 340 is not limited to this example.

[0092] (Negative electrode current collector) In this example, the negative electrode current collector 320 electrically connects the negative electrode lead 174 and the negative electrode active material layer 340. As the negative electrode current collector 320, a material that does not react with lithium or a material with poor reactivity with lithium is used.

[0093] In one embodiment, the negative electrode current collector 320 is composed of one or more metal materials, one or more conductive resins, one or more carbon materials, and combinations thereof. Examples of the above-mentioned metal materials include copper, aluminum, stainless steel, nickel, titanium, or alloys thereof.

[0094] In a modified example, the negative electrode current collector 320 comprises a resin support layer and a metal layer disposed on the surface of the support layer. Examples of the resin include polyethylene, polypropylene, polyethylene terephthalate, and polyimide. The metal layer may be made of copper, aluminum, stainless steel, nickel, titanium, or an alloy thereof. The metal layer may include a layer made of copper, aluminum, stainless steel, nickel, titanium, or an alloy thereof. The metal layer may be a foil or a plated layer.

[0095] Examples of the shape of the negative electrode current collector 320 include foil, mesh, punched metal, expanded metal, and combinations thereof. The thickness of the negative electrode current collector 320 is not particularly limited, but may be 5 to 200 μm. Preferably, the thickness of the negative electrode current collector 320 is 6 to 20 μm.

[0096] (Negative electrode active material layer) In this example, the negative electrode active material layer 340 is disposed on at least one surface of the negative electrode current collector 320. In this example, the negative electrode active material layer 340 is disposed on the first main surface 322 of the negative electrode current collector 320. The second main surface 344 of the negative electrode active material layer 340 may be in contact with the first main surface 322 of the negative electrode current collector 320.

[0097] In this example, the negative electrode active material layer 340 contains a negative electrode active material. The negative electrode active material layer 340 may be composed of foil-like or film-like negative electrode active material. Various metals are exemplified as negative electrode active material. The negative electrode active material may contain at least one metal selected from the group consisting of alkali metals, magnesium metals, zinc metals, and aluminum metals.

[0098] In one embodiment, the negative electrode active material may be at least one selected from the group consisting of alkali metals, alloys containing alkali metals, and composite oxides containing alkali metals. In a modified example, the negative electrode active material may be an alkali metal and / or a composite oxide containing alkali metals. In a further modified example, the negative electrode active material may be an alkali metal. The alkali metal may be lithium metal and / or sodium metal. As described above, these negative electrode active materials may have a foil-like or film-like shape.

[0099] The alkali metal may be lithium metal. The negative electrode 140 may be a lithium metal negative electrode. In this case, the storage battery 100 is the lithium metal storage battery described above, and the electrode potential of the negative electrode 140 with respect to Li / Li+ is, for example, 0.5V or less. The above electrode potential may be 0.2V or less, or 0.1V or less. If the storage battery 100 is a lithium-ion battery, the electrode potential of the negative electrode 140 with respect to Li / Li+ is, for example, 0.05V or more and 3.0V or less.

[0100] In one embodiment, the alkali metal is configured to deposit and dissolve alkali metal ions in the negative electrode 140. For example, if the storage battery 100 is a non-aqueous electrolyte secondary battery, alkali metal is deposited on the negative electrode 140 when the storage battery 100 is charged. For example, alkali metal is deposited on the surface of the negative electrode current collector 320. On the other hand, when the storage battery 100 is discharged, the alkali metal of the negative electrode 140 dissolves in the non-aqueous electrolyte 150. In this case, for example, one or more metal materials are used as the negative electrode current collector 320.

[0101] In one embodiment, the alkali metal is configured in the negative electrode 140 to absorb and release alkali metal ions. For example, if the storage battery 100 is a non-aqueous electrolyte secondary battery, the negative electrode 140 absorbs alkali metal ions when the storage battery 100 is being charged. For example, the negative electrode active material layer 340 absorbs alkali metal ions (this may be referred to as alkali metal ions being inserted into the negative electrode active material layer 340). On the other hand, when the storage battery 100 is being discharged, the negative electrode 140 releases alkali metal ions into the non-aqueous electrolyte 150.

[0102] In one embodiment, one or more carbon materials may be used as the negative electrode active material layer 340. That is, the negative electrode 140 may be a graphite negative electrode. In a modified example, one or more silicon materials may be used as the negative electrode active material layer 340. That is, the negative electrode 140 may be a silicon oxide negative electrode or a silicon negative electrode.

[0103] The negative electrode active material layer 340 may consist of a single layer or multiple layers. If the negative electrode active material layer 340 consists of multiple layers, it may include a first layer containing negative electrode active material and a second layer made of a conductive material. The second layer may contain less negative electrode active material than the first layer, or may not contain negative electrode active material at all. In this case, the second layer may be in contact with the negative electrode current collector 320, and the first layer may be electrically connected to the negative electrode current collector 320 via the second layer.

[0104] If the negative electrode active material layer 340 is composed of multiple layers, the negative electrode active material layer 340 may include a resin support layer and a layer containing the negative electrode active material. In this case, the layer containing the negative electrode active material may be formed on one surface of the support layer or on both surfaces of the support layer.

[0105] The thickness of the negative electrode active material layer 340 may be 1 to 500 μm, 10 to 200 μm, or 50 to 100 μm. When a foil-like or film-like alkali metal (sometimes referred to as alkali metal foil) is used as the negative electrode active material layer 340, the thickness of the alkali metal foil may be 10 to 200 μm or 50 to 100 μm. The thickness and / or mass of the alkali metal foil may be determined according to the content of the positive electrode active material in the positive electrode active material layer 240.

[0106] In one embodiment, the negative electrode active material layer 340 is made by processing the material used as the negative electrode active material into a foil or sheet. In a modified example, the negative electrode active material layer 340 is formed by depositing the material constituting the negative electrode active material layer 340 on at least one surface of a resin support layer by (i) slurry coating, (ii) physical vapor deposition (PVD) methods such as sputtering, vapor deposition, and ion plating, (iii) chemical vapor deposition (CVD), or (iv) atomic layer deposition (ALD).

[0107] In the electrode structure 110, the positive electrode 120 is positioned on the side of the first main surface 132 of the separator 130. On the other hand, the negative electrode 140 is positioned on the side of the second main surface 134 of the separator 130. In this case, the first main surface 342 of the negative electrode active material layer 340 may be in contact with the second main surface 134 of the separator 130. The negative electrode 140 is in contact with the functional layer 135 provided on the second main surface 134 of the separator 130.

[0108] (Example of modification) The negative electrode 140 does not have a negative electrode current collector 320. If the negative electrode 140 does not have a negative electrode current collector 320, the negative electrode active material layer 340 may have the function of the negative electrode current collector 320. Such a negative electrode 140 is used, for example, in a battery having an electrolyte containing alkali metal ions, or a battery using alkali metal ions as carriers. The above battery is manufactured, for example, by assembling a battery structure including the above negative electrode 140 and an electrolyte containing alkali metal ions into a battery housing. The above battery may also be a metal negative electrode battery.

[0109] When the above-described negative electrode 140 is incorporated into, for example, a storage battery 100 that uses alkali metal ions as a carrier, alkali metal is deposited on the surface of the negative electrode current collector 320 during charging of the storage battery 100. The alkali metal is derived, for example, from alkali metal ions contained in the electrolyte of the storage battery 100. This forms an alkali metal negative electrode active material layer 340. As a result, a negative electrode 140 is manufactured having a laminate in which the negative electrode current collector 320 and the negative electrode active material layer 340 are stacked in this order.

[0110] Figure 4 schematically shows an example of a separator 130. In this example, the separator 130 comprises a functional layer 135 and a base layer 440. The functional layer 135 contains nitrate-containing particles 138. The separator 130 has a first main surface 132 and a second main surface 134.

[0111] In this example, for the purpose of simplifying the explanation, the details of the separator 130 will be described using the example where the functional layer 135 is arranged on one side of the base layer 440. However, the separator 130 is not limited to this example. In a modified example, the functional layer 135 may be arranged on both sides of the base layer 440.

[0112] The base layer 440 is a region of the separator 130 that does not contain nitrate-containing particles 138. In other words, the base layer 440 may be a region of the separator 130 that remains uncoated with the coating liquid. In the example shown in Figure 4, since the coating liquid is applied from the second main surface 134 side of the separator 130, the base layer 440 remains on the first main surface 132 side of the separator 130.

[0113] In the modified example, the base layer 440 may not be provided. The entire separator 130 may be coated with the coating liquid to form the functional layer 135.

[0114] The thickness of the separator 130 may be less than the thickness of the negative electrode 140. The thickness of the separator 130 may be 0.1 μm or more, 0.2 μm or more, or 0.5 μm or more. The thickness of the separator 130 may be 20 μm or less, 50 μm or less, or 100 μm or less.

[0115] The separator 130 is positioned so that it is in contact with the functional layer 135 and the negative electrode 140. In the example shown in Figure 4, the first main surface 342 of the negative electrode 140 and the second main surface 134 of the separator 130 are facing each other.

[0116] Figure 5 schematically shows a modified example of the separator 130. In this example, the separator 130 includes a buffer layer 510.

[0117] The buffer layer 510 may be an area to which the coating liquid is applied and which does not contain nitrate-containing particles 138. The buffer layer 510 may be formed by applying a coating liquid that does not contain nitrates.

[0118] The buffer layer 510 may contain an inorganic material and a binder. The buffer layer 510 may contain only the inorganic material and / or only the binder.

[0119] The separator 130 is arranged so that the buffer layer 510 and the positive electrode 120 are in contact. In the example shown in Figure 5, the second main surface 224 of the positive electrode 120 and the first main surface 132 of the separator 130, on which the buffer layer 510 is provided, are facing each other.

[0120] Figure 6 schematically shows an example of the electrode structure 610. The electrode structure 610 is another example of the electrode structure 110. The electrode structure 610 differs from the electrode structure 110 in that it has a wound structure. The electrode structure 610 may have the same configuration as the electrode structure 110, except for the above-mentioned difference.

[0121] In this example, the electrode structure 610 is manufactured by winding a sheet in which a positive electrode 120, a separator 130, a negative electrode 140, and another separator 130 are stacked in this order into a roll. Although not shown in Figure 6, in this example as well, a functional layer 135 is provided on the surface of the separator 130 that is in contact with the negative electrode 140. The separator 130 may have a buffer layer 510 on the surface that is in contact with the positive electrode 120. In this example, a positive electrode tab 122 is provided at one end of the positive electrode 120. A negative electrode tab 142 is provided at one end of the negative electrode 140.

[0122] (Example of Modification) In this example, an example of an electrode structure 610 has been described, in which the electrode structure 610 comprises a single positive electrode tab 122 and a single negative electrode tab 142. However, the electrode structure 610 is not limited to this example. In a modification, the electrode structure 610 may have a plurality of negative electrode tabs 142. Also, the electrode structure 610 may have a plurality of positive electrode tabs 122.

[0123] Figure 7 schematically shows an example of a method for manufacturing a storage battery 100. In this example, an example of a method for manufacturing a storage battery 100 equipped with a separator 130, as described in relation to Figures 4 and 5, is described.

[0124] In this example, first, in step 710 (the step may be referred to as S), the negative electrode 140 is prepared. Specifically, for example, a foil-like or film-like active material containing an alkali metal is prepared. As described above, examples of the active material included in the negative electrode 140 include at least one selected from the group consisting of alkali metals, alloys containing alkali metals, and composite oxides containing alkali metals. The above active material may be an alkali metal or a composite oxide containing an alkali metal.

[0125] In this example, in step S720, the positive electrode 120 and the separator 130 are prepared. Specifically, a coating solution containing a dispersed nitrate is applied to a polyethylene film or the like, and after drying, it is cut to a predetermined size to prepare the separator 130 having a functional layer 135.

[0126] In this example, in step S730, the electrode structure 110 is assembled using the positive electrode 120, the separator 130, and the negative electrode 140. Specifically, the negative electrode 140 is placed on the side of the separator 130 that has the functional layer 135, and the positive electrode 120 is placed on the side opposite to the side with the functional layer 135. In this example, the negative electrode 140 is placed on the side of the second main surface 134 of the separator 130. The positive electrode 120 is also placed on the side of the first main surface 132 of the separator 130. The electrode structure 110 is assembled by repeating the above process. This results in an electrode structure 110 comprising the positive electrode 120, the separator 130, and the negative electrode 140.

[0127] In S730, if the functional layer 135 is provided on both sides of the separator 130, the orientation of the first main surface 132 and the second main surface 134 of the separator is irrelevant. When the functional layer 135 is provided on both sides of the separator 130, the side with the thicker functional layer 135 may be in contact with the negative electrode 140, or the side with the higher basis density of nitrate may be in contact with the negative electrode 140.

[0128] Next, in S740, the battery 100 is assembled using the electrode structure 110. Specifically, the electrode structure 110 and the non-aqueous electrolyte 150 are housed inside the battery case 160. For example, after the electrode structure 110 is placed inside the battery case 160, the non-aqueous electrolyte 150 is filled inside the battery case 160. This completes the battery 100.

[0129] Step 710 may be an example of a method for producing electrodes. Steps 710 to 740 may be an example of a method for producing a battery structure.

[0130] For the purpose of further explaining the storage battery 100, the details of the storage battery 100 will be described by the following embodiment. However, various modifications or improvements may be made to the following embodiment, and the storage battery 100 is not limited to the following embodiment.

[0131] (Preparation of coating solution 1-1) 0.1 g of carboxymethylcellulose (CMC, weight-average molecular weight 1 million, purity 98% or higher) and 9 g of deionized water were mixed and ultrasonically treated. Then, alumina (D) was added to the solution. ５０ Coating solution 1-1 was prepared by mixing 1 g of (0.2 μm particle, purity 98% or higher) and 0.001 g of ammonium polyacrylate solution (PAAAA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 44 w / w%), and then sonicating the mixture.

[0132] (Preparation of coating solution 1-2) As an inorganic material, boehmite (D ５０ Coating solution 1-2 was prepared in the same manner as coating solution 1-1, except that a particle with a value of 0.2 μm and a purity of 98% or higher was used.

[0133] (Preparation of coating solution 2-1) Lithium nitrate (LiNO) ３ A mixture of 2 g of Fujifilm Wako Pure Chemical Industries (98% purity) and 7 g of ion-exchanged water was prepared and subjected to ultrasonic treatment to obtain coating solution 2-1.

[0134] (Preparation of coating solution 2-2) 0.1 g of carboxymethylcellulose (CMC, weight-average molecular weight 1,000,000, purity 98% or higher) and 7 g of deionized water were mixed and sonicated. Then, lithium nitrate (LiNO) was added to the solution. ３ Coating solution 2-2 was obtained by adding 2g of Fujifilm Wako Pure Chemical Industries, Ltd. (98% purity) and subjecting it to ultrasonic treatment.

[0135] (Preparation of coating solution 2-7 from coating solution 2-3) Coating solution 2-7 was prepared from coating solution 2-3 in the same manner as the preparation of coating solution 2-2, except that the amounts of lithium nitrate and carboxymethylcellulose were changed.

[0136] (Preparation of coating solution 3-1) 0.1 g of carboxymethylcellulose (CMC, weight-average molecular weight 1,000,000, purity 98% or higher) and 7 g of deionized water were mixed and sonicated. Then, lithium nitrate (LiNO) was added to the solution. ３ Coating solution 3-1 was obtained by mixing 2 g of Fujifilm Wako Pure Chemical Industries, Ltd. (98% purity) with 0.01 g of polyether-modified silicone (PolySi, manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-355A) and then subjecting the mixture to ultrasonic treatment.

[0137] (Preparation of coating solution 3-2) Coating solution 3-2 was prepared in the same manner as coating solution 2-2, except that acrylic latex (ARL, manufactured by Murayama Chemical Research Institute, product name F-35) was used as the binder instead of carboxymethylcellulose.

[0138] (Preparation of coating solution 4-1) 0.1 g of carboxymethylcellulose (CMC, weight-average molecular weight 1,000,000, purity 98% or higher) and 7 g of deionized water were mixed and sonicated. Then, lithium nitrate (LiNO) was added to the solution. ３ , Fujifilm Wako Pure Chemical Industries, Ltd., 98% purity, 2g, alumina (D ５０ Coating solution 4-1 was prepared by mixing 1 g of (0.2 μm particle, purity 98% or higher) and 0.001 g of ammonium polyacrylate solution (PAAAA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 44 w / w%), and then sonicating the mixture.

[0139] (Preparation of coating solution 4-2) As an inorganic material, boehmite (D ５０ Coating solution 4-2 was prepared in the same manner as coating solution 4-1, except that a particle with a value of 0.2 μm and a purity of 98% or higher was used.

[0140] (Preparation of coating solution 4-3) 0.1 g of carboxymethylcellulose (CMC, weight-average molecular weight 1,000,000, purity 98% or higher) and 7 g of deionized water were mixed and sonicated. Then, lithium nitrate (LiNO) was added to the solution. ３ 2g of Fujifilm Wako Pure Chemical Industries, Ltd., 98% purity; 0.01g of polyether-modified silicone (PolySi, manufactured by Shin-Etsu Chemical Co., Ltd., product name KF-355A); alumina (D ５０ Coating solution 4-3 was prepared by mixing 1 g of (0.2 μm particle, purity 98% or higher) and 0.001 g of ammonium polyacrylate solution (PAAAA, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 44 w / w%), and then sonicating the mixture.

[0141] (Preparation of coating solution 4-4) As an inorganic material, boehmite (D ５０ Coating solution 4-4 was prepared in the same manner as coating solution 4-3, except that a particle with a value of 0.2 μm and a purity of 98% or higher was used.

[0142] (Preparation of coating solutions 4-5 and 4-6) Coating solutions 4-5 and 4-6 were prepared in the same manner as the preparation of coating solutions 4-1 and 4-2, except that acrylic latex (manufactured by ARL Murayama Chemical Research Institute, product name F-35) was used as the binder instead of carboxymethylcellulose.

[0143] (Preparation of coating solutions 5-2, 6-2, 7-2 and 8-2) As nitrate, lithium nitrate (LiNO) ３ Instead of ) cesium nitrate (CsNO) ３ ), silver nitrate (AgNO) ３ ), calcium nitrate (Ca(NO) ３ ) ２ ), indium nitrate (In(NO ３ ) ３ Coating solutions 5-2, 6-2, 7-2, and 8-2 were prepared in the same manner as the preparation of coating solution 2-2, except for the use of ).

[0144] (Production of nitrate 1) Lithium nitrate (LiNO) ３ A mixture of 6 g of lithium nitrate (98% purity, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 100 g of 1,2-dimethoxyethane was prepared and heated to 40°C to dissolve lithium nitrate. When this solution was cooled to 25°C, crystals precipitated. The precipitated crystals were filtered, washed with dimethyl carbonate (DMC), and dried at 80°C to obtain needle-shaped crystals of lithium nitrate. The obtained crystals were crushed in a mortar to obtain a fine powder of nitrate 1.

[0145] (Production of nitrate 5 from nitrate 2) As nitrate, lithium nitrate (LiNO) ３ Instead of ) cesium nitrate (CsNO) ３ ), silver nitrate (AgNO) ３ ), calcium nitrate (Ca(NO) ３ ) ２ ), indium nitrate (In(NO ３ ) ３ Except for using ), the fine powder of nitrate 5 was obtained from nitrate 2 by the same method as in the production of nitrate 1.

[0146] (Preparation of coating solution 9-1) 0.02 g of polyvinylidene fluoride (PVDF) and 4 g of N-methyl-2-pyrrolizinone (NMP) were mixed to obtain an NMP binder solution. Then, 0.2 g of fine powder of nitrate 1 was added to the solution and ultrasonic treatment was performed to prepare coating solution 9-1.

[0147] (Preparation of coating solution 9-5 from coating solution 9-2) Except for using fine powder of nitrates 2 to 5 obtained from (production of nitrate 5 from nitrate 2) instead of nitrate 1, coating solution 9-5 was prepared from coating solution 9-2 in the same manner as coating solution 9-1. Table 1 shows the prepared coating solutions 1-1 to 9-5. [Table 1]

[0148] (Separator Fabrication 1-1) After applying coating liquid 2-1 to the coated surface 1 (the surface in contact with the negative electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, the solvent was removed by vacuum drying at 80°C for 10 minutes, and the film was cut into a planar shape of 45 mm in length and 45 mm in width to fabricate a separator 1-1 with a functional layer.

[0149] (Separator preparation 1-2 to Separator preparation 4-5) Separators 1-2 to 4-5 were prepared using the same method as in separator preparation 1-1, except that coating liquids 2-2 to 9-5 shown in Table 2 were used instead of coating liquid 2-1. Subsequently, the thickness, porosity, and basis density of the functional layer of the prepared separators were measured. The measured thickness, porosity, and basis density of the functional layer are shown in Table 2.

[0150] (Measurement of Functional Layer Thickness) The thickness of the separator (45 mm x 45 mm) after applying each coating solution and the separator (45 mm x 45 mm) before coating were measured, and the difference was defined as the thickness of the functional layer. A contact-type thickness gauge was used for thickness measurement.

[0151] (Measured density of the functional layer) The measured density of the functional layer was calculated by dividing the weight of the functional layer by the volume of the functional layer. The weight of the functional layer was measured using an electronic balance to determine the weight of the separator (45 mm x 45 mm) after coating with each coating liquid and the separator (45 mm x 45 mm) before coating, and the difference was taken as the weight of the functional layer. The volume of the functional layer was calculated by multiplying the cross-sectional area of ​​the functional layer by the measured thickness of the functional layer.

[0152] (Theoretical density of the functional layer) The theoretical density of the functional layer was calculated using the ratio of the constituent components contained in the coating solution and the literature values ​​for the densities of the constituent components. The literature value for density was lithium nitrate = 2.38 g / cm³. ３ Cesium nitrate = 3.68 g / cm³ ３ , silver nitrate = 4.35g / cm ３ Calcium nitrate = 2.36 g / cm³ ３ Indium nitrate = 4.35 g / cm³ ３ Alumina = 3.9 g / cm³ ３ Boehmite = 3.0 g / cm³ ３ , CMC=1.5g / cm ３ , ARL=1.4g / cm ３ I used it.

[0153] (Porosity of the functional layer) The porosity of the functional layer was calculated using the following formula: Porosity = (1 - (Measured density of the functional layer) / (Theoretical density of the functional layer)) × 100 (%)

[0154] (Basis density of the functional layer) Basis density of the functional layer (g / cm³) ３ ) is the basis weight (g) of nitrate in the functional layer, and the volume (cm³) of the functional layer. ３ The amount of nitrate (g) was calculated by dividing by the volume of nitrate contained in the functional layer (cm³). ３ ) and the literature value for nitrate density (g / cm³) ３ It was calculated by multiplying by ). [Table 2]

[0155] (Separator Fabrication 2-1) Coating solution 1-1 was applied to the coated surface 2 (the surface in contact with the positive electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Next, coating solution 3-1 was applied to the coated surface 1 (the surface in contact with the negative electrode) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Separator 2-1, which has a functional layer and a buffer layer, was fabricated by cutting it into a planar shape of 45 mm in length and 45 mm in width.

[0156] (Separator preparation 2-2 to separator preparation 2-5) Separator 2-5 was prepared using the same method as in separator preparation 2-1, except that coating liquids 1-2 to 4-4 shown in Table 3 were used instead of coating liquid 1-1.

[0157] (Separator Fabrication 3-1) Coating liquid 1-1 was applied to the coated surface 1 (the surface in contact with the negative electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Next, coating liquid 3-1 was applied to the coated surface 1 using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Separator 3-1 with a functional layer was then fabricated by cutting it into a planar shape of 45 mm in length and 45 mm in width.

[0158] (Separator preparation 3-2) Separator 3-2 was prepared in the same manner as in separator preparation 3-1, except that coating liquid 1-2 was used instead of coating liquid 1-1.

[0159] (Separator Fabrication 3-3) Coating solution 1-1 was applied to the coated surface 1 (the surface in contact with the negative electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Next, coating solution 1-1 was applied to the coated surface 2 (the surface in contact with the positive electrode) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Furthermore, coating solution 3-1 was applied to the coated surface 1 using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Separator 3-3, which has a functional layer and a buffer layer, was fabricated by cutting it into a planar shape of 45 mm in length and 45 mm in width.

[0160] (Separator preparation 3-4) Separator 3-4 was prepared in the same manner as in separator preparation 3-3, except that coating liquid 1-2 was used instead of coating liquid 1-1.

[0161] (Separator Fabrication 3-5) Coating solution 1-1 was applied to the coated surface 1 (the surface in contact with the negative electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Next, coating solution 3-1 was applied to the coated surface 2 (the surface in contact with the positive electrode) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Furthermore, coating solution 3-1 was applied to the coated surface 1 using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Separator 3-5, which has functional layers on both sides, was fabricated by cutting it into a planar shape of 45 mm vertically and 45 mm horizontally.

[0162] (Separator preparation 3-6) Separator 3-6 was prepared in the same manner as in separator preparation 3-5, except that coating liquid 1-2 was used instead of coating liquid 1-1.

[0163] (Separator Fabrication 3-7) Coating solution 1-1 was applied to the coated surface 1 (the surface in contact with the negative electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Next, coating solution 1-1 was applied to the coated surface 2 (the surface in contact with the positive electrode) using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Furthermore, coating solution 3-1 was applied to the coated surface 1 using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. After that, coating solution 3-1 was applied to the coated surface 2 using the doctor blade method, and then the solvent was removed by vacuum drying at 80°C for 10 minutes. Separator 3-7, which has functional layers on both sides, was fabricated by cutting it into a planar shape of 45 mm vertically and 45 mm horizontally.

[0164] (Separator preparation 3-8) Separator 3-8 was prepared in the same manner as in separator preparation 3-7, except that coating liquid 1-2 was used instead of coating liquid 1-1.

[0165] (Separator preparation 4-6 to separator preparation 4-15) Separators 4-6 to 4-15 were prepared using the same method as in separator preparation 2-1 and 2-2, except that coating liquids 9-1 to 9-5 were used instead of coating liquid 3-1. [Table 3]

[0166] (Separator Fabrication 5-0) An uncoated separator was fabricated. Specifically, separator 5-0 shown in Table 4 was fabricated by cutting polyethylene film (Celgard, USA, #2320) into a flat shape of 45 mm in length and 45 mm in width.

[0167] (Separator preparation 5-1) After applying coating liquid 1-1 to the coated surface 2 (the surface in contact with the positive electrode) of a polyethylene film (Celgard, USA, #2320) using the doctor blade method, the solvent was removed by vacuum drying at 80°C for 10 minutes, and the separator 5-1 was prepared by cutting it into a flat shape of 45 mm in length and 45 mm in width.

[0168] (Separator preparation 5-2 to separator preparation 5-11) Separator 5-11 was prepared from separator 5-2 shown in Table 4, using the same method as in separator preparation 5-1, except that each coating liquid shown in Table 4 was applied to each coated surface of the polyethylene film. [Table 4]

[0169] (Preparation of test NCM cathode) An NCM cathode was prepared according to the following procedure. First, as the cathode active material, the median diameter (D) based on the number of particles was prepared. ５０ ) is 5 μm NCM (LiNi １／３ Mn １／３ Co １／３ O ２ We prepared the following: Carbon black and graphite as conductive additives. Polyvinylidene fluoride (PVDF) as a binder.

[0170] Next, PVDF and N-methyl-2-pyrrolidinone (NMP) were mixed to prepare 50 g of a PVDF-NMP solution. The PVDF content in the NMP solution was 10 wt%. Next, 85 g of NCM, 5 g of carbon black, and 5 g of graphite were mixed. Then, the above mixture was mixed with the 50 g of the PVDF-NMP solution to prepare 145 g of paint.

[0171] Next, the above-mentioned paint was applied to the surface of an aluminum foil with a thickness of 20 μm using the doctor blade method. By drying the above-mentioned paint at a temperature of 90°C, an aluminum foil with a positive electrode active material layer formed on it was obtained. After that, the above-mentioned aluminum foil was cut into a square of 40 mm in length and 40 mm in width, and terminals were welded to it. This created a positive electrode.

[0172] (Fabrication of Lithium Metal Anode) A lithium metal foil with a thickness of 100 μm and a purity of 99.5% or higher was prepared. The planar shape of the lithium metal foil was a square with dimensions of 40 mm in length and 40 mm in width. The lithium metal foil was placed on the anode current collector. Next, terminals were welded to the metal foil. This completed the fabrication of the lithium metal anode.

[0173] (Preparation of graphite anode) SCMG (registered trademark)-AR powder (manufactured by Showa Denko K.K.) was used as the artificial graphite, and natural graphite particles (average particle size 25 μm) (manufactured by Kansai Thermal Chemical Co., Ltd.) were used as the natural graphite. The artificial graphite and natural graphite were uniformly dispersed in NMP (polymeric polymer) in which PVDF (a binder) had been dissolved beforehand, and then NMP for viscosity adjustment was added to prepare a mixture paste of artificial graphite and natural graphite.

[0174] This paste was applied to copper foil (current collector), dried, and pressurized. After processing to a predetermined size (40 mm vertically, 40 mm horizontally), terminals were welded to obtain a graphite negative electrode. The solid content ratio in the negative electrode was set to artificial graphite powder:natural graphite powder:PVDF = 72:18:10 (mass ratio). The amounts of NMC positive electrode active material, artificial graphite, and natural graphite were adjusted so that the charging capacity of the graphite negative electrode was greater than that of the NMC positive electrode. The amount of coating was also adjusted to prevent lithium metal from precipitation on the graphite negative electrode during charging.

[0175] (Fabrication of silicon oxide anode) As silicon oxide powder, disproportionated silicon oxide powder (manufactured by Sigma-Aldrich Japan Co., Ltd., SiO2) is used. ｘ (x is 0.3 to 1.6, average particle size 5 μm), and MAG-D (particle size 20 μm or less) (manufactured by Hitachi Chemical Co., Ltd.) was used as the bulk artificial graphite powder. The mixed powder of silicon oxide powder and bulk artificial graphite powder was uniformly dispersed in NMP in which PVDF as a binder had been dissolved in advance, and Ketjenblack (conductive agent) was added and mixed. Furthermore, NMP for viscosity adjustment was added, and SiO ｘ A compound paste was prepared.

[0176] This paste was applied to copper foil (current collector), dried, and pressurized. After processing to a predetermined size (40 mm vertically, 40 mm horizontally), terminals were welded to obtain a silicon oxide negative electrode. The solid content ratio in the negative electrode was SiO ｘ The ratio of MAGD, conductive agent, and PVDF was set to 35:47:8:10 (mass ratio). Furthermore, the NMC cathode active material and SiO were adjusted so that the charging capacity of the silicon oxide anode was greater than that of the NMC cathode. ｘThe amount of powder was adjusted, and the coating amount was also adjusted to prevent lithium metal from depositing on the silicon oxide negative electrode during charging.

[0177] (Preparation of Silicon Anode) As the Si powder, a mixed powder of Si powder (average particle size: 10 μm / 6 μm = mass ratio 9 / 1) was used. The Si powder was uniformly dispersed in NMP in which PVDF, which is a binder, had been dissolved in advance, and then Ketjenblack (conductive agent 1) and vapor-phase carbon fiber (VGCF®, manufactured by Showa Denko) (conductive agent 2) were added and mixed. Furthermore, NMP for viscosity adjustment was added to prepare the Si mixture paste.

[0178] This paste was applied to copper foil (current collector), dried, and pressurized. After processing to a predetermined size (40 mm vertically, 40 mm horizontally), terminals were welded to obtain a silicon anode. The solid content ratio in the anode was Si powder:conductive agent 1:conductive agent 2:PVDF = 78:7:3:12 (mass ratio). The amounts of NMC positive electrode active material and Si powder were adjusted so that the charging capacity of the silicon anode was greater than that of the NMC positive electrode, and the amount of coating was adjusted so that lithium metal would not precipitate on the silicon anode during charging.

[0179] (Preparation of Electrolyte) The electrolyte used in Example 1 of the present invention was prepared by the following procedure. A mixed solvent of fluoroethylene carbonate (FEC, manufactured by Kishida Chemical Co., Ltd., purity 99.5%), dimethyl carbonate (DMC, manufactured by Kishida Chemical Co., Ltd., purity 99.5%), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE, manufactured by Tokyo Chemical Industry Co., Ltd., purity 95%) was mixed with lithium hexafluoride phosphate (LiPF6, manufactured by Kishida Chemical Co., Ltd., purity 99.9%) to a concentration of 12% by mass and dissolved to prepare the electrolyte used in Example 1.

[0180] (Example 1) Test pouch cells were prepared. Specifically, test pouch cells were prepared according to the following procedure.

[0181] (Preparation of test laminate) On the surface of the lithium metal negative electrode with the lithium foil, separator 1-1 was placed in a orientation such that the functional layer was in contact with the lithium foil. Next, the positive electrode was placed on separator 1-1 such that the surface of the positive electrode active material of the positive electrode was in contact with the side of separator 1-1 opposite to the functional layer. This resulted in a laminate in which the negative electrode, separator, and positive electrode were laminated in this order.

[0182] (Preparation of test pouch cell) First, the laminate described above was placed inside a bag-shaped aluminum laminate having an opening. Next, the electrolyte prepared in the above-mentioned electrolyte preparation was vacuum injected into the aluminum laminate. Then, the opening of the aluminum laminate was heated and sealed. This produced the test pouch cell described in Example 1 of Table 5.

[0183] (Examples 2 to 45) The test pouch cells described in Examples 2 to 45 in Table 5 were prepared by following the same procedure as in Example 1, except that the type of separator was changed. Specifically, instead of separator 1-1, separators 1-2 to 1-17, separators 2-1 to 2-5, separators 3-1 to 3-8, and separators 4-1 to 4-15 were used to prepare the test pouch cells described in Examples 2 to 45. [Table 5]

[0184] (Examples 46 to 57) The test pouch cells described in Examples 46 to 57 in Table 6 were prepared by following the same procedure as in Example 1, except that the type of negative electrode was changed. Specifically, a graphite negative electrode was used instead of a lithium metal negative electrode, and the test pouch cells described in Examples 46 to 57 were prepared using separators 1-2 to 1-7, separators 2-1 to 2-2, separators 4-6, 4-11, separators 3-3 and 3-4. [Table 6]

[0185] (Examples 58 to 69) The test pouch cells described in Examples 58 to 69 in Table 7 were prepared by following the same procedure as in Example 1, except that the type of negative electrode was changed. Specifically, a silicon oxide negative electrode was used instead of a lithium metal negative electrode, and the test pouch cells described in Examples 58 to 69 were prepared using separators 1-2 to 1-7, separators 2-1 to 2-2, separators 4-6, 4-11, separators 3-3 and 3-4. [Table 7]

[0186] (Examples 70 to 81) The test pouch cells described in Examples 70 to 81 in Table 8 were prepared by following the same procedure as in Example 1, except that the type of negative electrode was changed. Specifically, a silicon negative electrode was used instead of a lithium metal negative electrode, and the test pouch cells described in Examples 70 to 81 were prepared using separators 1-2 to 1-7, separators 2-1 to 2-2, separators 4-6, 4-11, separators 3-3 and 3-4. [Table 8]

[0187] (Comparative Example 1) A test pouch cell described in Comparative Example 1 of Table 9 was prepared by following the same procedure as in Example 1, except that the type of separator was changed. Specifically, the separator 5-0 obtained in (Separator Preparation 5-0) above, which was not coated with nitrate, was used.

[0188] (Comparative Examples 2 to 27) Except for changing the type of separator and the type of negative electrode, the test pouch cells described in Comparative Examples 2 to 27 in Table 9 were prepared following the same procedure as in Comparative Example 1. In Comparative Examples 2 to 4, separator 5-0, which is not coated with nitrate, was used, and the type of negative electrode was changed to prepare the test pouch cells. In Comparative Examples 5 to 15, separators 5-1 to 5-11 were used instead of separator 5-0, and lithium metal negative electrodes were used to prepare the test pouch cells. In Comparative Examples 16 to 27, separators 5-1, 5-3, 5-6, and 5-8 were used, and graphite negative electrodes, silicon oxide negative electrodes, or silicon negative electrodes were used instead of lithium metal negative electrodes to prepare the test pouch cells. [Table 9] (Evaluation) A cycle test was performed on each test pouch cell prepared in each example and comparative example. Specifically, the test pouch cells were charged and discharged at 0.1C in a 25°C environment, and the initial charge / discharge capacity was measured. Then, the ratio of the discharge capacity to the initial charge / discharge capacity after a predetermined number of charge / discharge cycles under the charge / discharge conditions shown in Tables 4 to 9 was calculated and defined as the discharge capacity retention rate (%). The evaluation results of the cycle tests in each example and comparative example are shown in Tables 4 to 9.

[0189] (1) Evaluation by porosity and basis density Comparative Examples 1 and 5 in Table 9 are examples using separators 5-0 and 5-1 that are not coated with nitrate. In contrast, Comparative Examples 6 and 7 in Table 9 are examples using separators 5-2 and 5-3 that have a functional layer containing nitrate, or nitrate and a binder, on the surface in contact with the negative electrode. Here, separators 5-2 and 5-3 used in Comparative Examples 6 and 7 both had a functional layer containing nitrate on the surface in contact with the negative electrode, but their cycle performance was worse than that of Comparative Examples 1 and 5.

[0190] The separator 5-2 used in Comparative Example 6 had a porosity of 96% in the functional layer, exceeding 95%. Furthermore, the separator 5-3 used in Comparative Example 7 had a porosity of 4% in the functional layer, below 5%, and a basis density of nitrate of 0.009 g / cm³. ３ And 0.01 g / cm³３ It is below that. On the other hand, the separators 1-1 to 1-7 used in Examples 1 to 7 in Table 5 all have a porosity in the functional layer in the range of 5% to 95%, and a basis density of nitrate of 0.01 g / cm³. ３ Above, 3.0g / cm ３ The range is as follows:

[0191] Examples 1 to 7 in Table 5 showed higher cycle characteristics than Comparative Examples 1, 5, 6, and 7. Thus, in this example, the cycle characteristics of the battery can be improved by setting the porosity and basis density of nitrate in the functional layer containing nitrate to values ​​within a predetermined range and arranging the functional layer on the surface in contact with the negative electrode.

[0192] (2) Evaluation by placing the functional layer on the surface in contact with the negative electrode. Comparative Examples 10, 11, and 15 in Table 9 all use separators 5-6, 5-7, and 5-11, where the functional layer containing nitrate is on the surface in contact with the positive electrode, and its porosity and basis density of nitrate are within the predetermined range described above. In contrast, Examples 1 to 45 in Table 5 all showed higher cycle characteristics than Comparative Examples 10, 11, and 15. Thus, the cycle characteristics of the storage battery can be improved by placing the functional layer on the surface in contact with the negative electrode rather than on the surface in contact with the positive electrode.

[0193] (3) Effects of inorganic materials Examples 8 to 13 in Table 4 contain inorganic materials in the functional layer containing nitrate. Examples 8 to 13 showed cycle characteristics equivalent to or better than Examples 1, 2 and 7, which do not contain inorganic materials. Thus, in this example, the cycle characteristics of the storage battery can be improved by including inorganic materials in the functional layer.

[0194] (4) Evaluation by type of salt Examples 14 to 17 in Table 4 use separators 1-14 to 1-17 containing cesium nitrate, silver nitrate, calcium nitrate, and indium nitrate as the functional layer nitrate, instead of lithium nitrate. Examples 14 to 17 all showed higher cycle efficiency than Comparative Examples 1, 6, and 7. Furthermore, Examples 14 to 17 showed cycle characteristics equivalent to or better than Example 2, which used separator 1-2 containing lithium nitrate. Thus, in this example, even when using nitrates other than lithium nitrate, the cycle characteristics of the storage battery can be improved by setting the porosity and basis density of the nitrate within a predetermined range.

[0195] (5) Evaluation by solvent of coating solution The batteries described in Examples 18 to 22 of Table 4 use NMP instead of water as the solvent for the coating solution and separators 4-1 to 4-5 using PDVF as the binder. Examples 18 to 22 all showed higher cycle efficiency than Comparative Examples 1, 6 and 7. Furthermore, Examples 18 to 22 showed cycle characteristics equivalent to or better than those of Examples 2 and 14 to 17. Thus, in this example, even when an organic solvent is used instead of water as the solvent for the coating solution, the cycle characteristics of the battery can be improved by keeping the porosity and basis density of nitrates within a predetermined range.

[0196] (6) Evaluation by providing a buffer layer Examples 23 and 24 in Table 4 use separators 2-1 and 2-2 which have a buffer layer containing a binder or inorganic material on the surface in contact with the positive electrode. Examples 23 and 24 showed higher cycle characteristics than Example 6 which does not have a buffer layer. Thus, in this example, the cycle characteristics of the storage battery can be further improved by having a buffer layer on the surface of the separator in contact with the positive electrode.

[0197] Similarly, Examples 28 to 37 in Table 4 also use separators 4-6 to 4-15 having a buffer layer containing a binder or inorganic material on the surface in contact with the positive electrode. Examples 28 to 32 contain alumina as the inorganic material in the buffer layer. Examples 33 to 37 contain boehmite as the inorganic material in the buffer layer. Examples 28 to 37 exhibit higher cycle characteristics than Examples 18 to 22. Thus, in this example, even when an organic solvent is used instead of water as the solvent for the coating solution, the cycle characteristics of the battery can be further improved by having a buffer layer on the surface of the separator in contact with the positive electrode.

[0198] (7) Evaluation by multiple coatings of coating solution Examples 38 to 45 in Table 4 use separators 3-1 to 3-8 in which the coating solution was applied in two separate applications. Examples 38 to 45 all showed higher cycle efficiency than Comparative Examples 1, 6 and 7. Thus, in this example, by changing the order in which the coating solution is applied, the porosity and basis density of nitrates in the functional layer of the separator can be adjusted, thereby improving the cycle characteristics of the storage battery.

[0199] (8) Comparative Example 2 in Evaluation Table 9, when a graphite anode is used, is an example in which separator 5-0, which is not coated with nitrate, is used and a graphite anode is used instead of a lithium metal anode. In contrast, Comparative Example 17, which uses separator 5-3 having a functional layer coated with nitrate on the surface in contact with the anode, showed no change in cycle characteristics. Thus, even if the separator contains nitrate, if the porosity or basis density of nitrate is not within a predetermined range, it does not affect the cycle characteristics.

[0200] Examples 46 to 51 in Table 6 use separators 1-1 to 1-7 coated with nitrate such that the porosity and basis density of nitrate are within a predetermined range, and use a graphite anode instead of a lithium metal anode. All of Examples 46 to 51 exhibit higher cycle characteristics than Comparative Examples 2 and 17.

[0201] Examples 52 to 57 in Table 6 use separators 2-1, 2-2, 4-6, 4-11, 3-3, and 3-4, which are coated with nitrate so that the porosity and basis density of nitrate are within a predetermined range, and which also have a buffer layer, and use a graphite anode instead of a lithium metal anode. Examples 52 to 57 all show higher cycle characteristics than Comparative Examples 2 and 17. Thus, even when using a graphite anode, the cycle characteristics of the battery can be improved by using a separator coated with nitrate so that the surface in contact with the anode has a predetermined porosity and basis density of nitrate.

[0202] (9) Comparative Example 3 in Evaluation Table 9, when a silicon oxide anode is used, is an example in which a separator 5-0 without nitrate coating is used and a silicon oxide anode is used instead of a lithium metal anode. In contrast, Comparative Example 21, which uses a separator 5-3 having a functional layer coated with nitrate on the surface in contact with the anode, showed no change in cycle characteristics. Thus, even if the separator contains nitrate, if the porosity or basis density of nitrate is not within a predetermined range, it does not affect the cycle characteristics.

[0203] Examples 58 to 63 in Table 7 use separators 1-1 to 1-7 coated with nitrate such that the porosity and basis density of nitrate are within a predetermined range, and use a silicon oxide anode instead of a lithium metal anode. All of Examples 58 to 63 exhibit higher cycle characteristics than Comparative Examples 3 and 21.

[0204] Examples 64 to 69 in Table 7 use separators 2-1, 2-2, 4-6, 4-11, 3-3, and 3-4, which are coated with nitrate so that the porosity and basis density of nitrate are within a predetermined range, and which also have a buffer layer, and use a silicon oxide anode instead of a lithium metal anode. Examples 64 to 69 all show higher cycle characteristics than Comparative Examples 3 and 21. Thus, even when a silicon oxide anode is used, the cycle characteristics of the battery can be improved by using a separator coated with nitrate so that the surface in contact with the anode has a predetermined porosity and basis density of nitrate.

[0205] (10) Comparative Example 4 in Evaluation Table 9, when a silicon anode is used, is an example in which a separator 5-0 without nitrate coating is used and a silicon anode is used instead of a lithium metal anode. In contrast, Comparative Example 25, which uses a separator 5-3 having a functional layer coated with nitrate on the surface in contact with the anode, showed no change in cycle characteristics. Thus, even if the separator contains nitrate, if the porosity or basis density of nitrate is not within a predetermined range, it does not affect the cycle characteristics.

[0206] Examples 70 to 75 in Table 8 use separators 1-1 to 1-7 coated with nitrate such that the porosity and basis density of nitrate are within a predetermined range, and use a silicon anode instead of a lithium metal anode. All of Examples 70 to 75 exhibit higher cycle characteristics than Comparative Examples 4 and 25.

[0207] Examples 76 to 81 in Table 8 use separators 2-1, 2-2, 4-6, 4-11, 3-3, and 3-4, which are coated with nitrate so that the porosity and basis density of nitrate are within a predetermined range, and which also have a buffer layer, and use a silicon anode instead of a lithium metal anode. All of Examples 76 to 81 show higher cycle characteristics than Comparative Examples 4 and 25. Thus, even when using a silicon anode, the cycle characteristics of the battery can be improved by using a separator coated with nitrate so that the surface in contact with the anode has a predetermined porosity and basis density of nitrate.

[0208] (11) Comparing Examples 1 to 81 and Comparative Examples 1 to 27 described in Summary Tables 5 to 9, it can be seen that the test pouch cell according to this embodiment has superior cycle characteristics compared to the test pouch cells of Comparative Examples 1 to 27, which use separators in which at least one of the porosity or basis density of nitrate is not within the predetermined range, by using a separator whose surface in contact with the negative electrode has a predetermined porosity and basis density of nitrate. Furthermore, it can be seen that the cycle characteristics are further improved when the separator has a buffer layer in addition to the functional layer, or when it contains inorganic materials.

[0209] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0210] It should be noted that the execution order of operations, procedures, steps, and stages in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these can be performed in any order unless the output of a previous process is used in a later process. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," "next," etc. for convenience, this does not mean that it is mandatory to perform the operations in that order.

[0211] 100...Battery, 110...Electrode structure, 120...Positive electrode, 122...Positive electrode tab, 130...Separator, 132...First main surface, 134...Second main surface, 135...Functional layer, 138...Particles, 140...Negative electrode, 142...Negative electrode tab, 150...Electrolyte, 160...Battery case, 162...Positive electrode terminal, 164...Negative electrode terminal, 172...Positive electrode lead, 174...Negative Electrode lead, 220... Positive electrode current collector, 222... First main surface, 224... Second main surface, 226... Side surface, 240... Positive electrode active material layer, 320... Negative electrode current collector, 322... First main surface, 324... Second main surface, 326... Side surface, 340... Negative electrode active material layer, 342... First main surface, 344... Second main surface, 346... Side surface, 440... Base layer, 510... Buffer layer, 610... Electrode structure

Claims

1. A separator for use in a secondary battery, comprising a functional layer containing a nitrate, provided on the surface in contact with the negative electrode of the secondary battery, wherein the porosity of the functional layer is 5% or more and 95% or less, and the basis density of the nitrate is 0.01 g / cm³. ３ Above, 3.0g / cm ３ The separator is as follows:

2. The separator according to claim 1, wherein the nitrate comprises at least one selected from lithium nitrate, potassium nitrate, cesium nitrate, sodium nitrate, silver nitrate, calcium nitrate, zinc nitrate, copper nitrate, magnesium nitrate, and indium nitrate.

3. The separator according to claim 1, wherein the basis weight of the nitrate contained in the functional layer is 0.1% or more and 100% or less of the mass of the functional layer.

4. The separator according to claim 1, wherein the thickness of the separator is 0.1 μm or more and 100 μm or less.

5. The separator according to claim 1, wherein the thickness of the separator is 0.2 μm or more and 50 μm or less.

6. The separator according to claim 1, wherein the thickness of the separator is 0.5 μm or more and 20 μm or less.

7. The basis density of the nitrate is 0.1 g / cm³. ３ Above, 3.0g / cm ３ The separator according to claim 1, wherein the following applies:

8. The basis density of the nitrate is 1.0 g / cm³. ３ Above, 3.0g / cm ３ The separator according to claim 1, wherein the following applies:

9. The surface density of the nitrate in the functional layer is 0.01 mg / cm². ２ Above, 100mg / cm ２ The separator according to claim 1, which is as follows:

10. The separator according to claim 1, wherein the porosity of the functional layer is 20% or more and 85% or less.

11. The separator according to claim 1, wherein the porosity of the functional layer is 35% or more and 75% or less.

12. The separator according to any one of claims 1 to 11, wherein the functional layer comprises an inorganic material having a mass of 0.1% or more and 80% or less of the mass of the functional layer, and the inorganic material comprises at least one selected from alumina, boehmite, silica, and titania.

13. A separator according to any one of claims 1 to 11, comprising a binder for supporting the nitrate on the separator, wherein the mass of the binder is 0.1% or more and 20% or less of the mass of the functional layer.

14. The separator according to claim 13, wherein the binder comprises at least one selected from polyvinylidene fluoride, acrylic latex, acrylic resin, polyacrylic acid, polyacrylic acid-styrene copolymer, styrene-butadiene rubber, polyvinyl alcohol, epoxy resin, sodium polyacrylate, polytetrafluoroethylene, polysiloxane, polyoxyethylene-methylpolysiloxane copolymer, polyimide, polyamide, polyamideimide, polyester, carboxymethylcellulose, cellulose derivatives, and polysulfone.

15. A separator according to any one of claims 1 to 11, comprising fibers for supporting the nitrate on the separator, wherein the mass of the fibers is 0.5% or more and 30% or less of the mass of the nitrate.

16. The separator according to claim 15, wherein the fiber is at least one selected from hollow fibers, nanofibers, porous polymer fibers, and cellulose fibers.

17. The separator according to any one of claims 1 to 11, comprising a buffer layer containing an inorganic material and a binder on the surface in contact with the positive electrode of the secondary battery.

18. A secondary battery comprising a separator as described in claim 1, a negative electrode in contact with the functional layer, and a positive electrode disposed at a distance from the negative electrode.

19. The secondary battery according to claim 18, wherein the functional layer is also provided on the surface of the separator that is in contact with the positive electrode.

20. The secondary battery according to claim 18, wherein the negative electrode is one of a lithium metal negative electrode, a graphite negative electrode, a silicon oxide negative electrode, and a silicon negative electrode.

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