Battery

Abstract

The present invention addresses the problem of providing a battery in which a polymer electrolyte can be used regardless of the potential window. The present invention provides a battery which comprises: a positive electrode; a negative electrode; a first electrolyte layer that is positioned between the positive electrode and the negative electrode; and a second electrolyte layer that is positioned between the first electrolyte layer and the positive electrode and / or between the first electrolyte layer and the negative electrode. The first electrolyte layer contains a polymer electrolyte. The polymer electrolyte contains at least a polymer and an alkali metal salt. The alkali metal salt is contained in an amount of 5 parts by mass to 200 parts by mass inclusive relative to 100 parts by mass of the polymer. The second electrolyte layer contains a porous base material and a nonaqueous electrolyte solution.

Description

battery

[0001] The present invention relates to batteries containing polymer electrolytes.

[0002] In recent years, lithium-ion secondary batteries (hereinafter sometimes referred to as LIBs) have been used in a variety of applications, such as mobile devices such as smartphones and mobile phones, hybrid vehicles, electric vehicles, and home storage batteries, and research and development related to these batteries has been actively conducted.

[0003] There is a strong demand for improved safety in LIBs, especially for applications such as electric vehicles. Conventional LIBs use flammable electrolytes, which can lead to battery combustion or explosion. For this reason, research into solid electrolytes that can contribute to improved safety is gaining momentum.

[0004] Solid electrolytes are solids that readily conduct ions and are generally classified into oxide-based solid electrolytes, sulfide-based solid electrolytes, and polymer-based solid electrolytes. Polymer-based solid electrolytes (hereinafter sometimes referred to as polymer electrolytes) have attracted attention due to their superior productivity and flexibility compared to sulfide-based and oxide-based solid electrolytes. Polymer electrolytes are broadly classified into three types: solid polymer electrolytes that conduct ions without the use of an ionizing agent, semi-solid polymer electrolytes that conduct ions in the presence of an ionizing agent, and gel polymer electrolytes that contain a high content of ionizing agent.

[0005] JP 2007-87958 A JP 2002-42872 A

[0006] Polymer electrolytes have increasing ionizing agent content and decreasing mechanical strength in the order of solid polymer electrolyte, semi-solid polymer electrolyte, and gel polymer electrolyte. Therefore, Patent Document 1 discloses a battery having a configuration of a positive electrode / gel polymer electrolyte / porous membrane / gel polymer electrolyte / negative electrode. The polymer electrolyte described in Patent Document 1 contains more than 200 parts by mass of ionizing agent per 100 parts by mass of polymer contained in the polymer electrolyte, and is therefore a gel polymer electrolyte as defined herein. Patent Document 2 also discloses a battery having a configuration of a positive electrode / microporous membrane / gel polymer electrolyte made of acrylonitrile copolymer / negative electrode. The polymer electrolyte described in Patent Document 2 also contains more than 200 parts by mass of ionizing agent per 100 parts by mass of polymer contained in the polymer electrolyte, and is therefore a gel polymer electrolyte as defined herein.

[0007] However, in the batteries having a structure in which a polymer electrolyte is in contact with an electrode as disclosed in Patent Documents 1 and 2, the design of the battery is limited by the potential window of the polymer electrolyte. For example, a polymer electrolyte using polyethylene oxide has a potential window of 4 V (vs. Li / Li ＋ It is known that at voltages above 1000 kJ / cm2, polyethylene oxide is oxidized, resulting in a decrease in charge / discharge efficiency.

[0008] In view of the above, an object of the present invention is to provide a battery in which the design of the battery is not limited by the potential window of the polymer electrolyte, that is, in which various polymer electrolytes can be used regardless of the potential window.

[0009] As a result of extensive research aimed at solving the above problems, the inventors have found a battery that can use various polymer electrolytes regardless of the potential window, and have arrived at the present invention.

[0010] That is, to solve the above problems, the present invention has the following configurations. (1) A battery having a positive electrode, a negative electrode, a first electrolyte layer located between the positive electrode and the negative electrode, and a second electrolyte layer located at least between the first electrolyte layer and the positive electrode and between the first electrolyte layer and the negative electrode, wherein the first electrolyte layer contains a polymer electrolyte, and the polymer electrolyte contains at least a polymer and an alkali metal salt, with the alkali metal salt content being 5 parts by mass to 200 parts by mass per 100 parts by mass of the polymer, and the second electrolyte layer contains a porous substrate and a non-aqueous electrolyte solution. (2) The battery described in (1) is preferably one in which the polymer electrolyte is a solid polymer electrolyte or a semi-solid polymer electrolyte. (3) The battery described in (1) or (2) is preferably one in which the glass transition temperature of the polymer contained in the polymer electrolyte is 40°C or higher. (4) Preferably, the battery according to (1) or (2) is one in which the polymer contained in the polymer electrolyte is one selected from the group consisting of polyether, polyarylene sulfide, polycarbonate, and copolymers containing these. (5) Preferably, the battery according to (1) or (2) is one in which the polymer contained in the polymer electrolyte is polyarylene sulfide. (6) Preferably, the battery according to (5) is one in which the polyarylene sulfide is a polyarylene sulfide copolymer having a unit represented by the chemical formula -(Ar-S)- (Ar is an arylene group) as a constituent unit, and the constituent unit includes a constituent unit having Ar represented by chemical formula (A) and a constituent unit having Ar represented by at least one selected from the group consisting of chemical formulas (B) to (G).

[0011]

[0012] (R1 and R2 are substituents selected from an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R1 and R2 may be the same or different. R3 and R4 are substituents selected from a hydrogen atom, an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R3 and R4 may be the same or different. Y is an alkylene group, O, CO, SO, SO２ Selected from.)

[0013] According to the present invention, it is possible to provide a battery that can use various polymer electrolytes regardless of the potential window.

[0014] FIG. 1 is a schematic cross-sectional view of a structure provided in a battery according to one embodiment of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the embodiments described below.

[0016] (Polymer Electrolyte) The first electrolyte layer used in the battery of the present invention contains a polymer electrolyte, and the polymer electrolyte contains at least a polymer and an alkali metal salt. In the present invention, the polymer electrolyte refers to a substance that is in a solid state at room temperature and easily migrates ions when an external electric field is applied. In the present invention, the term "solid" refers to a substance that maintains its shape regardless of the shape of the container.

[0017] From the viewpoint of ionic conductivity as an electrolyte for battery applications and charge / discharge performance of the battery, the ionic conductivity of the polymer electrolyte of the present invention at 25° C. is 10 －６ It is preferable that the viscosity is 10 S / cm or more, and more preferably 10 －５ S / cm or more, more preferably 10 －４ S / cm or more.

[0018] On the other hand, for example, in a non-aqueous electrolyte secondary battery disclosed in JP 2005-129480 A, which is composed of a separator film and a non-aqueous electrolyte (i.e., an ionizing agent and an alkali metal salt), the ionic conductivity of the solid portion of the separator film (i.e., the portion composed of the polymer contained in the separator film) is 10 －８ S / cm, which is significantly different from the ionic conductivity of the solid-state polymer electrolyte of the present invention.

[0019] This difference is presumed to be due to the difference in the degree of dispersion of the polymer and alkali metal salt in the solid portion. Due to the difference in ionic conductivity of the solid portion, the Gurley air permeability of the separator film, etc., is 10,000 sec / 100 cm in the Gurley air permeability measurement (JIS P8117:2009). ３ If the porosity is insufficient, the non-aqueous electrolyte will not pass through the separator film and the separator film cannot be used as a separator. However, in the case of a polymer electrolyte, the Gurley air permeability is 10,000 sec / 100 cm. ３ Even in the above cases, alkali metal ions pass through the polymer electrolyte, and the polymer electrolyte can be used as a separator.

[0020] The polymer electrolyte used in the battery of the present invention may be impregnated with an ionizing agent as described below.

[0021] The polymer electrolytes used in the battery of the present invention are classified into three types depending on the amount of ionizing agent contained therein: solid polymer electrolytes, semi-solid polymer electrolytes, and gel polymer electrolytes.

[0022] The solid polymer electrolyte does not contain an ionizing agent, or if it does contain an ionizing agent, the content of the ionizing agent is less than 1 part by mass per 100 parts by mass of the polymer contained in the polymer electrolyte. The semi-solid polymer electrolyte intentionally contains an ionizing agent, and the content of the ionizing agent is 1 part by mass or more and 200 parts by mass or less per 100 parts by mass of the polymer contained in the polymer electrolyte. The gel polymer electrolyte contains an ionizing agent in an amount greater than 200 parts by mass per 100 parts by mass of the polymer contained in the polymer electrolyte.

[0023] The polymer electrolyte used in the present invention is preferably a solid polymer electrolyte or a semi-solid polymer electrolyte because of the ease of laminating the electrolyte layer.

[0024] (Polymer contained in polymer electrolyte) As long as the polymer electrolyte used in the battery of the present invention exhibits ionic conductivity, the polymer contained in the polymer electrolyte (hereinafter sometimes referred to as the polymer of the polymer electrolyte) is not limited.

[0025] Preferred examples of the polymer of the polymer electrolyte include polyether, polyester, acrylic resin, polyarylene sulfide, polycarbonate, polyamide, polyimide, and fluororesin. More preferred examples include polyethylene oxide, polypropylene oxide, polyethylene terephthalate, polyacrylonitrile, polymethyl methacrylate, polyphenylene sulfide, polyethylene carbonate, polypropylene carbonate, nylon 6, nylon 66, and polyvinylidene fluoride, as well as copolymers containing at least one of the above-mentioned polymers.

[0026] The polymer of the polymer electrolyte is preferably one selected from the group consisting of polyether, polyarylene sulfide, polycarbonate, polyimide, polyamide, and copolymers containing any of these, from the viewpoint that it is preferable to form a solid polymer electrolyte or a semi-solid polymer electrolyte.

[0027] Furthermore, the polymer of the polymer electrolyte is preferably one selected from the group consisting of polyether, polyarylene sulfide, polycarbonate, and copolymers containing these.

[0028] From the viewpoint of heat resistance, the glass transition temperature of the polymer in the polymer electrolyte is preferably 40° C. or higher. When the glass transition temperature of the polymer is 40° C. or higher, the heat resistance of the first electrolyte layer is high, and as a result, the heat resistance of the battery is high. Preferred examples of polymers having a glass transition temperature of 40° C. or higher include polyarylene sulfide, polyimide, and polyamide.

[0029] The polymer of the polymer electrolyte is preferably polyarylene sulfide.

[0030] Furthermore, it is particularly preferable that the polyarylene sulfide is a polyarylene sulfide copolymer having as a constituent unit a unit represented by the chemical formula --(Ar--S)-- (Ar is an arylene group).

[0031] The structural unit preferably includes a structural unit having Ar represented by the following chemical formula (A), and a structural unit having Ar represented by at least one selected from the group consisting of chemical formulas (B) to (G):

[0032]

[0033] (R1 and R2 are substituents selected from an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R1 and R2 may be the same or different. R3 and R4 are substituents selected from a hydrogen atom, an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R3 and R4 may be the same or different. Y is an alkylene group, O, CO, SO, SO ２ In the polyarylene sulfide copolymer, the copolymerization rate of the structural units having Ar represented by at least one selected from the group consisting of chemical formulas (B) to (G) is preferably 1 mol% or more and 50 mol% or less, relative to 100 mol% of the structural units. When the copolymerization rate is 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, the melting point of the polyarylene sulfide is significantly lowered, allowing for lower processing temperatures when producing a polymer electrolyte, leading to improved ionic conductivity and quality stability of the polymer electrolyte. On the other hand, when the copolymerization rate is 50 mol% or less, more preferably 40 mol% or less, recovery of the polyarylene sulfide copolymer from the reaction solution after completion of the polymerization reaction of the polyarylene sulfide copolymer tends to be more efficient.

[0034] The copolymerization rate is the same as the molar ratio of the amount of the dihalogenated aromatic compounds corresponding to Ar represented by formulas (B) to (G) added to the total molar amount of the dihalogenated aromatic compounds represented by the chemical formula Cl-(Ar)-Cl added during polymerization.

[0035] The polyarylene sulfide may contain branched units or crosslinked units represented by the following formulas (H) to (J) as long as it contains a unit represented by the chemical formula -(Ar-S)- as a main constituent unit.

[0036]

[0037] The copolymerization rate of these branched units or crosslinked units is preferably in the range of 0 to 1 mol % relative to 100 mol % of the structural unit represented by the chemical formula --(Ar--S)--.

[0038] The polyarylene sulfide copolymer may be any of a random copolymer, a block copolymer, and a mixture thereof.

[0039] The synthesis method of the polyarylene sulfide copolymer is not particularly limited, and examples thereof include a method of reacting a sulfidizing agent with a dihalogenated aromatic compound in an organic polar solvent, a method of melt-reacting a diiodo aromatic compound with sulfur in the absence of a solvent, etc. Among these, the former polymerization method, which is industrially adopted, is preferred from the viewpoint of versatility.

[0040] The polyarylene sulfide preferably has a melting point of 300°C or lower. By setting the melting point of the polyarylene sulfide to 300°C or lower, more preferably 270°C or lower, and even more preferably 250°C or lower, the processing temperature during film formation can be lowered. Furthermore, film formation becomes possible in a temperature range lower than the decomposition temperature of the alkali metal salt. The lower limit of the melting point is not particularly limited, but if the amount of copolymerization component of polyarylene sulfide increases due to a lower melting point, the recoverability of the polyarylene sulfide copolymer from the reaction solution after polyarylene sulfide polymerization tends to decrease, so the melting point is preferably 150°C or higher, more preferably 200°C or higher.

[0041] The lower the crystallinity of the polyarylene sulfide, the more preferable. This is because the ionizing agent is impregnated into the amorphous regions of the polyarylene sulfide, forming ion conduction paths and achieving high ion conductivity. Specifically, the crystallinity is preferably 30% or less. More preferably, it is 15% or less. The lower limit of the crystallinity is not particularly limited, and the crystallinity may be 0%, i.e., the polyarylene sulfide may be composed only of amorphous regions. The crystallinity is calculated by dividing the heat of fusion (J / g) determined from the melting peak area detected by a differential scanning calorimeter (DSC) by the heat of fusion of 146.2 (J / g) when PPS is completely crystallized.

[0042] The method for identifying the polymer contained in the polymer electrolyte is not particularly limited, and the following methods can be used in combination. Only the first electrolyte layer, i.e., the polymer electrolyte layer, is recovered from the battery. The polymer electrolyte may be analyzed as is, or the insoluble matter after extraction of the alkali metal salt and the ionizing agent may be used for analysis. Infrared absorption spectroscopy (IR), NMR, GC-MS, etc. can be used to identify the polymer.

[0043] (Alkali Metal Salt) From the viewpoint of ionic conductivity, it is important that the polymer electrolyte used in the battery of the present invention contains an alkali metal salt. The alkali metal salt is a salt formed by ionic bonding between an alkali metal ion and a counter anion.

[0044] Examples of the alkali metal ions include lithium ions, sodium ions, potassium ions, magnesium ions, and calcium ions.

[0045] The alkali metal salt preferably includes lithium or sodium salts, specifically lithium hydroxide (LiOH), lithium carbonate (Li ２ CO ３ ), lithium perchlorate (LiClO ４ ), lithium tetrafluoroborate (LiBF ４ ), lithium hexafluorophosphate (LiPF ６), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), sodium hexafluorophosphate (NaPF ６ ), sodium tetrafluoroborate (NaBF ４ ), sodium perchlorate (NaClO ４ The alkali metal salt contained in the polymer electrolyte more preferably contains at least one selected from the group consisting of LiTFSI and LiFSI, from the viewpoint of high ionic dissociation.

[0046] The alkali metal salt may be a mixture of several types of alkali metal salts in any ratio.

[0047] The content of the alkali metal salt in the polymer electrolyte needs to be 5 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the polymer contained in the polymer electrolyte. When the content of the alkali metal salt is 5 parts by mass or more and 200 parts by mass or less, the ionic conductivity of the polymer electrolyte is exhibited. From the viewpoint of good ionic conductivity, the content of the alkali metal salt is preferably 10 parts by mass or more and 150 parts by mass or less, and more preferably 20 parts by mass or more and 120 parts by mass or less.

[0048] The analytical and quantitative analysis method for the alkali metal salt contained in the polymer electrolyte is not particularly limited, and the following methods can be used in combination. Only the first electrolyte layer, i.e., the polymer electrolyte layer, is recovered from the battery. The alkali metal salt may be extracted from the polymer electrolyte with a solvent and analyzed as needed. Depending on the type of polymer, the polymer electrolyte may be freeze-pulverized before extraction. The alkali metal salt may be quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES), nuclear magnetic resonance (NMR), liquid chromatography mass spectrometry (LC-MS), ion chromatography (IC), or the like.

[0049] (Ionizing Agent) The ionizing agent can bond with an alkali metal salt in the amorphous portion of the polymer electrolyte to form a phase composed of a polymer, an alkali metal salt, and the ionizing agent, which has higher ionic conductivity than a phase composed of a polymer and an alkali metal salt.

[0050] As the ionizing agent, cyclic esters, chain esters, cyclic ethers, chain ethers, etc. are used, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), γ-butyrolactone (γBL), 2-methyl-γ-butyrolactone, acetyl-γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane (DME), 1,2-ethoxyethane, diethyl ether, ethylene glycol dialkyl ether, diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether, dipropyl carbonate, methyl butyl carbonate, methyl propyl Preferred examples of the organic solvent include alkyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, alkyl propionate esters, dialkyl malonate esters, alkyl acetate esters, tetrahydrofuran (THF), alkyltetrahydrofuran, dialkylalkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran, 1,3-dioxolane, alkyl-1,3-dioxolane, 1,4-dioxolane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, methyl propionate, ethyl propionate, phosphate triesters, and N-methyl-2-pyrrolidone, as well as derivatives and mixtures thereof.

[0051] From the viewpoint of ionic conductivity, the molar ratio of the ionizing agent to the alkali metal salt is preferably 20 or less, more preferably 16 or less. There is no particular restriction on the lower limit, but it is preferably 1 or more, more preferably 3 or more.

[0052] Furthermore, for ease of laminating the electrolyte layer, it is preferable that the amount of ionizing agent is such that the polymer electrolyte does not become a gel polymer electrolyte, that is, the amount of ionizing agent is 200 parts by mass or less per 100 parts by mass of the polymer contained in the polymer electrolyte.

[0053] The method for analyzing and quantifying the ionizing agent contained in the polymer electrolyte is not particularly limited, and the following methods can be used in combination. Only the first electrolyte layer, i.e., the polymer electrolyte layer, is recovered from the battery. The ionizing agent may be extracted from the polymer electrolyte with a solvent and analyzed as needed. Depending on the type of polymer, the polymer electrolyte may be freeze-pulverized before extraction. Gas chromatography / mass spectrometry (GC-MS), NMR, etc. can be used to quantify the ionizing agent.

[0054] (Porous substrate) The second electrolyte layer used in the battery of the present invention includes a porous substrate and a non-aqueous electrolyte solution. The porous substrate is not particularly limited as long as it has through-holes, the non-aqueous electrolyte solution described below can penetrate the porous portion of the porous substrate, and the positive electrode or negative electrode does not come into direct contact with the first electrolyte layer. Preferred examples of the porous substrate include paper, nonwoven fabric, and microporous membrane. Preferred examples of the material include glass, polyolefin, polyimide, polyamide, polyphenylene sulfide, and cellulose.

[0055] From the viewpoints of productivity and availability, it is preferable to use a microporous membrane made of polyolefin, and it is more preferable to use a microporous membrane containing a polyethylene resin, a polypropylene resin, or at least one of them as the main component. Here, for example, a microporous membrane containing a polyethylene resin as the main component means that the mass of the polyethylene resin is more than 50% by mass and not more than 100% by mass, when the total mass of the microporous membrane is 100% by mass.

[0056] The polyethylene resin or the propylene resin means a polymer in which the total content of ethylene- or propylene-derived components is more than 50% by mass and not more than 100% by mass, when the total mass of the resin polymer is 100% by mass.

[0057] Preferred examples of the polyethylene resin include a homopolymer consisting of ethylene alone, and a copolymer in which a chain olefin (α-olefin) such as propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, or 1-eicosene is copolymerized with ethylene.

[0058] The polypropylene resin is preferably a homopolymer consisting of propylene alone, or an ethylene-propylene copolymer, an ethylene-propylene-butene copolymer, or a propylene-butene copolymer.

[0059] The polyolefin resin may be a single substance or a mixture of two or more different polyolefin resins.

[0060] The porous substrate may contain other resin components besides polyethylene and polypropylene as needed. Examples of the other resin components include heat-resistant resins. The porous substrate may also contain various additives, such as antioxidants, heat stabilizers, antistatic agents, ultraviolet absorbers, antiblocking agents, fillers, crystal nucleating agents, and crystallization retarders, as long as the effects of the present invention are not impaired.

[0061] The thickness of the porous substrate used in the present invention is not particularly limited, but is preferably 1 μm or more and 20 μm or less, more preferably 1 to 10 μm.

[0062] If the thickness of the porous substrate is 1 μm or more, adhesion to the electrode is ensured, and in the case of a microporous polyolefin membrane, melt shrinkage at or above the melting point can be prevented, and contact between the first electrolyte layer and the electrode can be prevented. If the thickness is 20 μm or less, the resistance of the second electrolyte layer can be suppressed, and a thinner thickness is preferred as long as it does not fall below the lower limit of 1 μm.

[0063] (Non-aqueous electrolyte) The non-aqueous electrolyte used in the present invention is composed of an ionizing agent and an alkali metal salt, but is not particularly limited, and ionizing agents and alkali metal salts used in conventional lithium ion batteries can be used. Preferred examples of the ionizing agent contained in the non-aqueous electrolyte include compounds similar to the ionizing agents used in the polymer electrolyte. Multiple types of ionizing agents can be mixed in any ratio.

[0064] The alkali metal salt contained in the non-aqueous electrolyte solution is preferably a compound similar to the alkali metal salt used in the polymer electrolyte. The alkali metal salt contained in the non-aqueous electrolyte solution more preferably contains at least one of lithium tetrafluoroborate and lithium hexafluorophosphate. A mixture of multiple types of alkali metal salts in any ratio may be used.

[0065] (Positive Electrode and Negative Electrode) The positive electrode and negative electrode used in the battery of the present invention are not particularly limited as long as they can absorb and release alkali metals. The positive electrode and negative electrode each contain at least a positive electrode active material and may also contain a conductive material, a binder, etc.

[0066] Preferred examples of the negative electrode active material include carbon materials such as activated carbon, natural graphite, artificial graphite, graphite, acetylene black, ketjen black, furnace black, channel black, thermal black, soft carbon, hard carbon, mesocarbon microbeads, mesocarbon microfiber, mesoporous carbon, carbon nanotubes, fullerene, graphene, and carbon fiber; alloy materials such as silicon, silicon oxide, tin, tin oxide, aluminum, and indium; oxide materials such as lithium titanate and lithium niobate; and lithium metal, and one or more of these can be used.

[0067] The positive electrode active material is LiAl ｘ Co ｙ Ni ｚ Mn ｗ O ２ and oxides represented by x + y + z + w = ​​1, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ w ≤ 1, LiFePO ４ , LiMn ｘ Fe １－ｘ O ４ and the like are preferred examples, and one or more of these can be used.

[0068] Preferred examples of the conductive material include acetylene black, ketjen black, carbon nanotubes, fullerenes, graphene, carbon fibers, etc., and one or more of these can be used. Alternatively, an active material having low conductivity and having a carbon coating applied to the surface thereof by a CVD method or the like may be used.

[0069] Preferred examples of the binder include styrene-butadiene copolymer, polyimide, polyamideimide, polyvinylidene fluoride, etc., and one or more of these can be used. Furthermore, a binder that acts as a thickener, such as carboxymethyl cellulose, can also be used, or these can be used in combination with the above binders.

[0070] The electrode of the present invention can be manufactured as follows, although there are no limitations as long as the effects of the present invention are not impaired. The active material, conductive material, and binder are coated on a current collector together with a solvent to form a slurry, which is then dried, pressed, and other processes to form a slurry, and slit into a predetermined length and width. The electrode used in the battery of the present invention may be a double-sided electrode having active materials on both sides of the current collector.

[0071] (Battery Configuration) The battery of the present invention has a positive electrode, a negative electrode, a first electrolyte layer located between the positive electrode and the negative electrode, and a second electrolyte layer located at least either between the first electrolyte layer and the positive electrode or between the first electrolyte layer and the negative electrode.

[0072] 1 is a schematic cross-sectional view of a structure of a battery according to one embodiment of the present invention. The battery of the present invention has a positive electrode 1 and a negative electrode 2, with a first electrolyte layer 3 between the positive electrode 1 and the negative electrode 2. The battery of the present invention further has a second electrolyte layer 4 located between the first electrolyte layer 3 and the positive electrode 1, and a second electrolyte layer 5 located between the first electrolyte layer 3 and the negative electrode 2.

[0073] By providing the second electrolyte layer between the positive electrode or negative electrode and the first electrolyte layer, the battery is one in which the first electrolyte layer is not exposed to the positive electrode potential or negative electrode potential, and various polymer electrolytes can be used regardless of the potential window of the first electrolyte layer, i.e., the polymer electrolyte.

[0074] In the present invention, the second electrolyte layer may be located at least one between the first electrolyte layer and the positive electrode or between the first electrolyte layer and the negative electrode. However, the second electrolyte layer may be located both between the first electrolyte layer and the positive electrode and between the first electrolyte layer and the negative electrode. This configuration is preferable because it suppresses exposure of the first electrolyte layer to both the positive electrode potential and the negative electrode potential. In this configuration, the battery of the present invention includes multiple second electrolyte layers. The second electrolyte layer sandwiched on the positive electrode side and the second electrolyte layer sandwiched on the negative electrode side may use the same porous substrate and nonaqueous electrolyte, or different porous substrates and nonaqueous electrolytes. Furthermore, only the porous substrate may be different and the same nonaqueous electrolyte may be used, or only the nonaqueous electrolyte may be different and the same porous substrate may be used. When different porous substrates and nonaqueous electrolytes are used on the positive electrode side and the negative electrode side, it is preferable to use a porous substrate and nonaqueous electrolyte with high oxidation resistance on the positive electrode side and a porous substrate and nonaqueous electrolyte with high reduction resistance on the negative electrode side.

[0075] The battery of the present invention may have any structure such as a single layer, a laminated layer, or a wound structure, as long as it has the configuration of the present invention.

[0076] The battery of the present invention may take the form of a coin battery, a laminated battery, a cylindrical battery, a prismatic battery, etc. Laminated batteries, cylindrical batteries, and prismatic batteries are particularly preferred for increasing the battery capacity or for connecting multiple batteries to form a module.

[0077] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0078] [Measurement Method] (1) Measurement of Glass Transition Temperature The glass transition temperature was determined by differential scanning calorimetry (DSC). Using 3 to 10 mg of the target polymer, the temperature was raised from 20°C to 300°C at a rate of 10°C / min, and the glass transition temperature was calculated from the results. When the glass transition temperature was not observed above 40°C, the glass transition temperature was determined to be below 40°C. When the glass transition temperature of the polymer was 40°C or higher, the heat resistance of the first electrolyte layer was high, and as a result, the heat resistance of the battery was high.

[0079] (2) Evaluation of Ionic Conductivity The ionic conductivity of the first electrolyte layer, i.e., the polymer electrolyte, was measured by the following method. The polymer electrolyte was punched with a 10 mm diameter Thomson blade, or if punching was not possible, it was molded into a size of 10 mm diameter. The thickness was measured and then set in a pressure holder (LN-Z2-HF-PH series, manufactured by Toyo Corporation). Then, using an impedance measuring device (4990EDMS-120K, manufactured by Toyo Corporation), an AC voltage of 100 Hz to 100 MHz was applied at 25°C, and the impedance was measured using the complex impedance method to obtain a Nyquist plot. From the obtained Nyquist plot, the resistance value (R) was read, and the ionic conductivity (σ) was calculated using the following formula (1) together with the measured thickness (D) and the sample area (S) in contact with the measurement electrode.

[0080]

[0081] The sample area is 78.5 mm because it is punched out to a diameter of 10 mm. ２ The average value of the three samples was calculated.

[0082] (3) Evaluation of charge / discharge efficiency Whether or not a battery can use a polymer electrolyte regardless of the potential window was determined by the charge / discharge efficiency when the following charge / discharge test was conducted. The charge / discharge test was conducted under the following conditions in the order of charge, discharge, charge, and discharge. The charge / discharge efficiency was calculated by dividing the capacity at the second discharge by the capacity at the second charge and multiplying the result by 100. A charge / discharge efficiency of 95 or higher was rated A, a charge / discharge efficiency of 80 or higher but less than 95 was rated B, and a charge / discharge efficiency lower than that was rated C. Charging: The battery was charged at a constant current of 0.2 mA at 35°C to 4.2 V, and then charged at a constant voltage until the voltage reached 0.02 mA. Discharging: The battery was discharged at a constant current of 0.2 mA at 35°C to 3.0 V.

[0083] (4) Evaluation of Polymer Electrolyte Composition The methods for identifying the polymer contained in the polymer electrolyte and quantifying the alkali metal salt and ionizing agent contained in the polymer electrolyte are not particularly limited, and methods appropriate for the sample may be used. Here, the polymer electrolyte used in the examples was analyzed by the following means.

[0084] That is, the polymer contained in the polymer electrolyte was identified by IR measurement and identified from the spectrum.

[0085] The alkali metal salts were extracted from the polymer electrolyte with a solvent such as acetonitrile or water and identified by ion chromatography. The content of the alkali metal salts was quantified by the following method. The polymer electrolyte was burned and the generated gas was absorbed into pure water in which an internal standard had been dissolved to prepare a solution. The solution was analyzed by ion chromatography. The content of the alkali metal salts was calculated from the mass of the burned polymer electrolyte and the quantitative value of fluorine.

[0086] The content of the ionizing agent was quantified by the following method. The polymer electrolyte was immersed in acetonitrile for 20 hours to obtain an acetonitrile solution in which the soluble components were eluted. This acetonitrile solution was quantified by GC-MS, and the amount of the ionizing agent was calculated.

[0087] [Constituent Components] (PEO) Polyethylene glycol 500000 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used as the PEO. The glass transition temperature of the PEO was less than 40°C.

[0088] (PAS1) A polyarylene sulfide composed of 100 mol % of constitutional units represented by the chemical formula -(Ar-S)-, in which Ar is composed of 100 mol % of paraphenylene sulfide units represented by the following chemical formula (A), was designated PAS1. The glass transition temperature of PAS1 was 93°C.

[0089]

[0090] (PAS2) A copolymer composed of 100 mol % of constitutional units represented by the chemical formula -(Ar-S)-, in which Ar is 90 mol % of paraphenylene sulfide units represented by the following chemical formula (A) and 10 mol % of metaphenylene sulfide units represented by the following chemical formula (C) in which R3 and R4 are both hydrogen, was used as PAS2. The glass transition temperature of PAS2 was 84°C.

[0091]

[0092] (PAS3) A copolymer composed of 100 mol % of constitutional units represented by the chemical formula -(Ar-S)-, in which Ar is 65 mol % of paraphenylene sulfide units represented by the following chemical formula (A) and 35 mol % of metaphenylene sulfide units represented by the following chemical formula (C) in which R3 and R4 are both hydrogen, was used as PAS3. The glass transition temperature of PAS3 was 51°C.

[0093]

[0094] (PAN) Polyacrylonitrile (manufactured by Sigma-Aldrich) was used as PAN. The glass transition temperature of PAN was 123°C.

[0095] (PPC) Poly(propylene carbonate) (Sigma-Aldrich) was used as the PPC. The glass transition temperature of the PPC was less than 40°C.

[0096] (Alkali Metal Salt) Lithium bis(trifluoromethanesulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the alkali metal salt.

[0097] (Ionizing Agent) Gamma-butyrolactone (Kishida Chemical Co., Ltd.) was used as the ionizing agent.

[0098] (Porous substrate 1) A microporous film F12CD1 (manufactured by Toray Industries, Inc.) made of polyethylene resin was used as the porous substrate 1.

[0099] (Porous Substrate 2) A glass filter GC-50 (manufactured by ADVANTEC) was used as the porous substrate 2.

[0100] (Electrolyte Solution 1) In a glove box with a dew point of −40° C. or less, a nonaqueous electrolyte solution was prepared by dissolving lithium tetrafluoroborate in a solvent mixed with gamma butyrolactone and ethylene carbonate in a volume ratio of 4:1 to a concentration of 2 M, to prepare electrolyte solution 1.

[0101] (Electrolyte Solution 2) In a glove box with a dew point of −40° C. or less, a nonaqueous electrolyte solution was prepared by dissolving lithium hexafluorophosphate to a concentration of 1 M in a solvent obtained by mixing ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate in a volume ratio of 3:3:4. This was used as electrolyte solution 2.

[0102] (Positive electrode) A positive electrode sheet using lithium cobalt oxide (LiCoO) manufactured by Hosen Co., Ltd. as the active material was cut into a diameter of 14 mm and used as the positive electrode (coating weight: 2.7 mAh / cm ２ ).

[0103] (Negative electrode) A negative electrode sheet manufactured by Hosensha, which uses graphite as an active material, was cut into a diameter of 16 mm and used as the negative electrode (coating weight: 3.6 mAh / cm ２ ).

[0104] [Examples 1 to 5] PEO and alkali metal salts were weighed in the combinations and mass ratios shown in Table 1 and dissolved in acetonitrile so that the PEO was 10 mass%. The acetonitrile solution of PEO and alkali metal salt was dropped onto a Teflon (registered trademark) substrate and spread evenly using an applicator set to a clearance of 160 μm. The applied solution was dried with hot air at 40°C for 4 hours and then peeled off from the glass substrate. Finally, the solution was vacuum dried at 50°C for 48 hours to obtain a polymer electrolyte film. When an ionizing agent was impregnated, the ionizing agent was then dropped in the mass ratio shown in Table 1 to obtain a polymer electrolyte film. The polymer electrolyte films used in the batteries of Examples 1 to 5 had excellent ionic conductivity and were suitable for use in batteries.

[0105] A coin battery was fabricated by stacking a positive electrode, porous substrate 1, the polymer electrolyte, porous substrate 1, and a negative electrode in this order in a dry room with a dew point of -40°C or less, and appropriately dripping the electrolyte solution. A 2032 type coin battery with a diameter of 20 mm and a thickness of 3.2 mm was used, and the porous substrate and polymer electrolyte were cut to a diameter of 19 mm. Also, 20 μL of electrolyte solution 1 was dripped immediately after stacking the positive electrode and immediately before stacking the negative electrode. The batteries fabricated as described above were designated Examples 1 to 5. The batteries of Examples 1 to 5 were rated A for charge / discharge efficiency.

[0106] [Examples 6 to 12] Polyarylene sulfide and alkali metal salt were weighed in the combinations and mass ratios shown in Table 1 and melt-kneaded at 300°C for 5 minutes. The melt-kneaded mixture was then heat-pressed at 300°C for 10 seconds to form a film, which was immediately water-cooled. The film obtained as described above was vacuum-dried at 80°C for 12 hours in a dry room with a dew point of -40°C or less. An ionizing agent was added to the dried film obtained as described above, and the film was impregnated at 80°C to achieve the mass ratio shown in Table 1. A polymer electrolyte film was obtained as described above. The polymer electrolyte films used in the batteries of Examples 6 to 12 had excellent ionic conductivity and were suitable for use in batteries.

[0107] Hereinafter, batteries were prepared in the same manner as in Example 1 except for using the porous substrate and nonaqueous electrolyte solution shown in Table 2, and were designated as Examples 6 to 12. In Example 8, the porous substrate was laminated only on the positive electrode side, and in Example 9, the porous substrate was laminated only on the negative electrode side. The batteries of Examples 6, 7, and 10 to 12 were rated A for charge / discharge efficiency. The batteries of Examples 8 and 9 were rated B for charge / discharge efficiency.

[0108] Comparative Example 1 A polymer electrolyte was prepared in the same manner as in Example 1. The ionic conductivity of the polymer electrolyte film used in the battery of Comparative Example 1 was excellent, and from the viewpoint of the internal resistance of the battery, it was suitable for use in batteries. A coin battery was prepared by stacking a positive electrode, the polymer electrolyte, and a negative electrode in this order in a dry room with a dew point of −40° C. or less, and appropriately dripping the electrolyte solution. A 2032-type coin battery was used, and the polymer electrolyte was cut to a diameter of 19 mm. 20 μL of electrolyte solution 1 was dripped immediately after stacking the positive electrode and immediately before stacking the negative electrode. The battery prepared as described above was designated Comparative Example 1. The charge / discharge efficiency of the battery of Comparative Example 1 was rated C.

[0109] Comparative Example 2 was a battery prepared in the same manner as in Example 7, except for using the mass ratios shown in Table 1. In the battery of Comparative Example 2, the mass ratio of the polymer and alkali metal salt contained in the polymer electrolyte was less than 5 parts by mass of alkali metal salt per 100 parts by mass of polymer, and the ionic conductivity of the polymer electrolyte used in Comparative Example 2 was low. From the viewpoint of the internal resistance of the battery, it was not suitable for use in a battery. The charge / discharge efficiency of the battery of Comparative Example 2 was rated C.

[0110] Example 13 PAN and alkali metal salts were weighed out in the combinations and mass ratios shown in Table 1 and dissolved in an ionizing agent to achieve the mass ratios shown in Table 1. This solution was stirred at 100°C for 2 hours to obtain a gel polymer electrolyte. The gel polymer electrolyte obtained as described above was crushed between two glass plates to obtain a gel polymer electrolyte film. The polymer electrolyte film used in the battery of Example 13 had excellent ionic conductivity and was suitable for use in batteries.

[0111] Thereafter, a battery was produced in the same manner as in Example 1, and designated as Example 13. In the battery of Example 13, the lamination of the gel polymer electrolyte film and the porous substrate was difficult, and the charge / discharge efficiency was rated B.

[0112] Example 14 PPC and alkali metal salts were weighed in the combinations and mass ratios shown in Table 1, and dissolved in acetonitrile so that the PPC concentration was 10 mass%. The acetonitrile solution of PPC and alkali metal salt was transferred to an Al cup, dried with hot air at 80°C for 4 hours, and then vacuum dried at 80°C for 24 hours. An ionizing agent was added dropwise to the solution in the mass ratio shown in Table 1, to obtain a polymer electrolyte film. The polymer electrolyte film used in the battery of Example 14 had excellent ionic conductivity and was suitable for use in batteries.

[0113] Thereafter, a battery was fabricated in the same manner as in Example 1, and designated as Example 14. The battery of Example 14 was rated A in charge / discharge efficiency.

[0114]

[0115]

[0116] 1 Positive electrode 2 Negative electrode 3 First electrolyte layer 4 Second electrolyte layer 5 Second electrolyte layer

Claims

1. A battery having a positive electrode, a negative electrode, a first electrolyte layer located between the positive electrode and the negative electrode, and a second electrolyte layer located at least one between the first electrolyte layer and the positive electrode and between the first electrolyte layer and the negative electrode, wherein the first electrolyte layer contains a polymer electrolyte, and the polymer electrolyte contains at least a polymer and an alkali metal salt, with the alkali metal salt content being 5 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the polymer, and the second electrolyte layer contains a porous substrate and a non-aqueous electrolyte solution.

2. The battery according to claim 1, wherein the polymer electrolyte is a solid polymer electrolyte or a semi-solid polymer electrolyte.

3. The battery according to claim 1 or 2, wherein the glass transition temperature of the polymer contained in the polymer electrolyte is 40°C or higher.

4. The battery according to claim 1 or 2, wherein the polymer contained in the polymer electrolyte is one selected from the group consisting of polyether, polyarylene sulfide, polycarbonate, and copolymers containing any of these.

5. The battery according to claim 1 or 2, wherein the polymer contained in the polymer electrolyte is polyarylene sulfide.

6. The battery according to claim 5, wherein the polyarylene sulfide is a polyarylene sulfide copolymer having units represented by the chemical formula -(Ar-S)- (Ar is an arylene group) as structural units, and the structural units include a structural unit having Ar represented by chemical formula (A) and a structural unit having Ar represented by at least one selected from the group consisting of chemical formulas (B) to (G). (R1 and R2 are substituents selected from an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R1 and R2 may be the same or different. R3 and R4 are substituents selected from a hydrogen atom, an alkyl group, an alkoxy group, an amino group, a carboxyl group, and a hydroxyl group, and R3 and R4 may be the same or different. Y is an alkylene group, O, CO, SO, SO ２ Selected from.)

Images