Alkali-ion-conducting solid electrolyte and method for producing the same, separator for nonaqueous electrolyte secondary battery and method for producing the same, and nonaqueous electrolyte secondary battery

Abstract

An alkali metal ion-conducting solid electrolyte comprises an organic polymer having a sulfonic acid alkali metal salt group. The sulfonic acid alkali metal salt group can be part of an alkyl sulfonic acid alkali metal salt group represented by the formula: -R-SO3X (R is an alkylene group, X is an alkali metal atom). The organic polymer can be a polysaccharide derivative. The mass (EW value) of the organic polymer per mole of the sulfonic acid alkali metal salt group is, for example, 168 g / mol or more and 300 g / mol or less.

Description

Technical Field

[0001] This invention relates primarily to alkali metal ion-conducting solid electrolytes used as materials for non-aqueous electrolyte secondary batteries. Background Technology

[0002] Patent Document 1 discloses a liquid retainer for a lithium secondary battery, characterized in that it is used to allow an organic electrolyte to permeate or impregnate an electrode assembly formed by winding or stacking an organic electrolyte retainer between a positive electrode plate and a negative electrode plate, with the liquid retainer serving as a separator, so that the absorption and release of lithium ions can be repeated. The liquid retainer is a multilayer structure having at least two layers of hydrophilic fiber layers with different porosities. The porosity of the fiber layer on the interface side with the negative electrode plate is less than the porosity of the fiber layer on the interface side with the positive electrode plate. The overall average porosity of these fiber layers is 50% or more.

[0003] Patent Document 2 discloses a solid polymer electrolyte membrane, characterized in that it is a membrane composed of sulfonyl cellulose obtained by sulfonyl alkylation of cellulose, and the membrane is cross-linked by a cross-linking agent. Furthermore, Patent Document 2 proposes using this solid polymer electrolyte membrane in a fuel cell.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2013 / 128652

[0007] Patent Document 2: Japanese Patent Publication No. 2010-218742 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In the field of non-aqueous electrolyte secondary batteries, efforts are being made to separate the positive and negative electrodes while ensuring lithium-ion conduction between them. By separating the positive and negative electrodes, the movement of leachates or byproducts from one electrode to the other can be limited, which is expected to suppress side reactions. In addition, by using electrolytes with different compositions suitable for the positive and negative electrode sides respectively, improvements can be made to battery durability, power characteristics, and other aspects.

[0010] The liquid retainer for lithium secondary batteries in Patent Document 1 is made of a fiber layer, therefore, it cannot restrict the movement of substances other than lithium ions between the positive and negative electrodes.

[0011] The solid polymer electrolyte membrane in Patent Document 2 has proton conductivity but not lithium-ion conductivity, and therefore cannot be applied to non-aqueous electrolyte secondary batteries.

[0012] Solution for solving the problem

[0013] One aspect of the present invention relates to an alkali metal ion-conducting solid electrolyte comprising an organic polymer having sulfonic acid alkali metal salt groups.

[0014] Another aspect of the present invention relates to a separator for a non-aqueous electrolyte secondary battery, which comprises the above-mentioned alkali metal ion-conducting solid electrolyte.

[0015] Another aspect of the present invention relates to a non-aqueous electrolyte secondary battery comprising: a positive electrode, a negative electrode, a separator for the non-aqueous electrolyte secondary battery sandwiched between the positive electrode and the negative electrode, a first electrolyte in contact with the positive electrode, and a second electrolyte in contact with the negative electrode, wherein the composition of the first electrolyte and the second electrolyte is different.

[0016] Another aspect of the present invention relates to a non-aqueous electrolyte secondary battery comprising: a positive electrode, a negative electrode, a separator sandwiched between the positive and negative electrodes, and an electrolyte in contact with the positive and negative electrodes, wherein at least one of the positive and negative electrodes comprises the aforementioned alkali metal ion conductive solid electrolyte.

[0017] Another aspect of the present invention relates to a method for manufacturing an alkali metal ion-conducting solid electrolyte, comprising the following steps: adding a haloalkyl sulfonate to an alkaline liquid containing a raw material organic polymer having multiple hydroxyl groups, wherein at least one hydrogen atom of the aforementioned hydroxyl group is replaced with an alkyl sulfonate group as shown in the formula: -R-SO3X (R is an alkylene group and X is an alkali metal atom).

[0018] Another aspect of the present invention relates to a method for manufacturing a separator for a non-aqueous electrolyte secondary battery, comprising a step of molding the above-mentioned alkali metal ion-conductive solid electrolyte into a sheet shape.

[0019] The effects of the invention

[0020] The alkali metal ion conductive solid electrolyte of the present invention can both separate the positive electrode and the negative electrode and ensure the conduction of alkali metal ions between them.

[0021] The novel features of the invention are set forth in the appended claims, but the invention, in terms of both its structure and content, along with its other objects and features, will be better understood from the following detailed description with reference to the accompanying drawings. Attached Figure Description

[0022] Figure 1 The perspective view shows a portion of the structure of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention, with the portion cut away. Detailed Implementation

[0023] [Alkali metal ion conductive solid electrolyte]

[0024] The alkali metal ion-conducting solid electrolyte of the present invention comprises an organic polymer (hereinafter referred to as LSP) having a sulfonic acid alkali metal salt group (e.g., lithium sulfonate group). LSP can be readily synthesized, for example, by introducing a sulfonic acid alkali metal salt group or a sulfonate group (-SO3H) into the raw organic polymer and then replacing its hydrogen atoms with alkali metals such as Li, Na, or K. The sulfonic acid alkali metal salt group (-SO3X: ​​X is an alkali metal atom) undertakes the hopping of alkali metal ions, imparting alkali metal ion conductivity to the organic polymer.

[0025] The raw material organic polymer can be fitted with sulfonate or sulfonyl groups. For example, the raw material organic polymer can have multiple hydroxyl groups. The hydroxyl groups can be replaced with sulfonyl or sulfonate groups or substituents thereof by various methods.

[0026] The energy-weighted polymer (EW) of the organic polymer per mole of the sulfonic acid alkali metal salt can be above 168 g / mol and below 300 g / mol. The lower the EW value, the better the conductivity of the alkali metal ions. To obtain an LSP with a low EW value, a starting organic polymer with as many hydroxyl groups as possible can be used. Polysaccharides can be used as the starting organic polymer. LSPs synthesized from polysaccharides are derivatives of polysaccharides.

[0027] Polysaccharides are a general term for polymers with a structure in which multiple monosaccharide molecules are linked together by glycosidic bonds. Examples of basic polysaccharide structures that can be used include aldoses, ketoses, pyranoses, and furans. Monosaccharide molecules (monomers) that constitute polysaccharides include trioses, tetraoses, pentoses, hexoses, and heptaoses. Ideally, these include pentoses, pentyloses, hexyloses, and hexyloses. Specific examples of polysaccharides include cellulose, hemicellulose, pectin, alginic acid, pullulan, mannan, xanthan gum, guar gum, starch, glycogen, chitin, dextran, agarose, carrageenan, heparin, hyaluronic acid, glucomannan, or their derivatives (salts, esters, ethers, amides, etc.). Cellulose, in particular, has excellent heat resistance, is abundant, and can be obtained inexpensively.

[0028] Derived from organic polymer raw materials, LSPs can also possess multiple hydroxyl groups. The hydrogen atoms of these hydroxyl groups can be replaced by alkali metal atoms. This can further enhance the alkali metal ion conductivity of the LSP.

[0029] The alkali metal sulfonate group can be a part of the alkali metal sulfonate group represented by the formula: -R-SO3X (R is an alkylene group, X is an alkali metal atom). Here, the alkylene group R can be, for example, an alkylene group having 1 or more carbon atoms and less than 10 carbon atoms. The alkylene group R can be, for example, methylene, ethylene, n-propylene, n-butylene, n-pentylene, or n-hexylene.

[0030] Separator for non-aqueous electrolyte secondary batteries

[0031] LSPs can be molded into sheets to manufacture separators for non-aqueous electrolyte secondary batteries. Common separators include microporous membranes, paper, and nonwoven fabrics. However, dense membranes are needed to separate the positive and negative electrodes. Dense membranes containing LSPs are utilized as separators that both separate the positive and negative electrodes and allow the conduction of alkali metal ions between them.

[0032] For example, a dense film containing LSP can be obtained by using a solution in a solvent in which LSP is dissolved. LSPs with sulfonic acid alkali metal salts are water-soluble. Aqueous solutions containing LSP can be molded into dense films by various methods. For example, a dense film can be obtained by coating an aqueous solution containing LSP onto a flat surface of a substrate sheet and allowing water to evaporate from the coating.

[0033] The separator can be non-porous. Non-porous means that, unlike a typical separator, it does not have holes or gaps that allow electrolyte movement. However, non-porous means substantially non-porous, allowing for unavoidable pinholes, etc.

[0034] Non-porous separators have very high air permeability. The air permeability (air resistance) of the separator can be, for example, 10,000 seconds / 100 mL or more. The air permeability can be measured, for example, according to "21.2 Air permeability B method (Gurley test method)" (JIS P 8117) specified in JIS C2300, using a type B test apparatus (Gurley air permeability meter).

[0035] Dense membranes containing LSP can be, for example, membranes containing LSP at a content of 70% or more by mass, membranes containing LSP at a content of 95% or more by mass, or 100% LSP.

[0036] The thickness of the dense film containing LSP can be, for example, 0.001 μm or more and 100 μm or less, 0.01 μm or more and 90 μm or less, 0.1 μm or more and 80 μm or less, or 1 μm or more and 70 μm or less.

[0037] LSP containing a dense film of an organic polymer having lithium sulfonate groups, for example, shown at 25°C, is 1.0 × 10⁻⁶. - 4 S / cm or higher, further 1.0×10 -3 S / cm or higher (or 2.0×10) -3 The ionic conductivity (e.g., lithium-ion conductivity) is above S / cm. It should be noted that if ordinary cellulose is molded into a dense membrane, the ionic conductivity of that membrane is 10.-8 Below S / cm.

[0038] [LSP Manufacturing Method]

[0039] The manufacturing method of LSP will be further explained below. However, the following method is only one example, and LSPs can be synthesized by various other methods.

[0040] (i) First, prepare the raw material organic polymer (e.g., polysaccharides) and organic solvent, dissolving the base in the organic solvent and dissolving or dispersing the raw material organic polymer in the organic solvent to prepare the reaction solution. The organic solvent can be any solvent that can dissolve the base; for example, protic solvents such as alcohols, ethers, esters, etc., can be used. The base can be NaOH, KOH, LiOH, etc., but there are no particular limitations.

[0041] (ii) Next, a haloalkyl sulfonate is added to the reaction solution during stirring, replacing at least one hydrogen atom of the hydroxyl group of the starting organic polymer with an alkyl sulfonate group as shown in the formula: -R-SO3X (R is an alkylene group, X is an alkali metal atom). For example, a bromoalkyl sulfonate can be used as the haloalkyl sulfonate. Specifically, sodium 2-bromoethylsulfonate, potassium 2-bromoethylsulfonate, lithium 2-bromoethylsulfonate, etc., can be used. The reaction solution can also be heated to promote the substitution reaction. The temperature of the reaction solution can be, for example, 50°C to 80°C. The reaction time is not particularly limited; for example, it can be carried out for more than 10 hours (ideally 50 to 100 hours) to ensure the reaction proceeds fully.

[0042] (iii) Next, the organic polymer infused with alkyl sulfonate group (-R-SO3X) is filtered and dried.

[0043] When the alkali metal atom X is other than Li (Na, K, etc.), it can be ion-exchanged to Li. The organic polymer with introduced alkyl sulfonate groups is water-soluble. An aqueous solution is prepared by dissolving the water-soluble polymer in water. When this solution is contacted with a strongly acidic ion-exchange resin, the alkali metal atom is replaced with a hydrogen atom, yielding an organic polymer with sulfonyl alkyl groups. Next, lithium hydroxide (LiOH) is added to the acidic aqueous solution for neutralization, thereby replacing the hydrogen atoms of the sulfonyl group with Li, generating an LSP with lithium alkyl sulfonate groups.

[0044] [Non-aqueous electrolyte secondary battery]

[0045] (First Embodiment)

[0046] The non-aqueous electrolyte secondary battery of this embodiment includes: a positive electrode, a negative electrode, a separator containing an LSP sandwiched between the positive and negative electrodes, and an electrolyte in contact with the positive and negative electrodes. By using the LSP-containing separator, the movement of leachates or byproducts from one of the positive and negative electrodes to the other is restricted, and side reactions are suppressed. As a result, improvements can be made in battery durability, power characteristics, etc.

[0047] LSP-containing separators can be used in combination with conventional microporous membranes, papermaking, nonwoven fabrics, etc. (hereinafter also referred to as conventional separators). For example, LSP-containing separators can be used in combination with conventional separators. Alternatively, an aqueous solution containing LSP can be coated on the surface of one or both conventional separators, and the water can be evaporated from the coating to form a composite separator of conventional separator and LSP.

[0048] As an example of the structure of a non-aqueous electrolyte secondary battery, one can exemplify a structure in which an electrode assembly, consisting of a positive and a negative electrode wound together with a separator, is housed together with the electrolyte in a casing. However, this is not a limitation, and other forms of electrode assemblies can also be used. For example, a stacked electrode assembly, consisting of a positive and a negative electrode layered together with a separator, can be used. The shape of the non-aqueous electrolyte secondary battery is also not limited; for example, it can be cylindrical, square, coin-shaped, button-shaped, laminated, etc.

[0049] (Second Implementation)

[0050] The non-aqueous electrolyte secondary battery of this embodiment includes: a positive electrode, a negative electrode, a separator containing an LSP sandwiched between the positive and negative electrodes, a first electrolyte in contact with the positive electrode, and a second electrolyte in contact with the negative electrode. The first electrolyte and the second electrolyte have different compositions.

[0051] The first electrolyte has a composition suitable for the positive electrode side, and the second electrolyte has a composition suitable for the negative electrode side. For example, the first electrolyte has a composition with excellent oxidation resistance, and the second electrolyte has a composition with excellent reduction resistance. By using a separator containing an LSP, not only is the movement of leachates or byproducts from one of the positive and negative electrodes to the other restricted, but the movement of the first electrolyte towards the negative electrode side and the movement of the second electrolyte towards the positive electrode side are also suppressed. This allows for further improvements in battery durability, power characteristics, and other aspects.

[0052] In the case of a wound battery, for example, a first electrolyte can be immersed in the positive electrode and a second electrolyte can be immersed in the negative electrode. Then, the positive and negative electrodes are wound together with a separator containing an LSP to form an electrode assembly.

[0053] The space for storing the positive electrode can be separated from the space for storing the negative electrode. An example of such a structure is the inside-out structure. An inside-out battery has a cylindrical positive electrode and a cylindrical negative electrode. The other electrode is embedded within one of the cylindrical positive and negative electrodes. Inside-out structures include alkaline dry cell types and spike types, but are not limited to these.

[0054] (Third Implementation)

[0055] The non-aqueous electrolyte secondary battery of this embodiment includes: a positive electrode, a negative electrode, a separator containing an LSP sandwiched between the positive electrode and the negative electrode, and an electrolyte in contact with the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode has an LSP.

[0056] For example, at least one of the positive electrode compound and the negative electrode compound can contain an LSP. Furthermore, at least a portion of the surface of the positive electrode active material particles contained in the positive electrode compound can be pre-coated with an LSP, and at least a portion of the surface of the negative electrode active material contained in the negative electrode compound can also be pre-coated with an LSP. Additionally, an LSP coating can be formed on the surface of both the positive and negative electrodes. This suppresses side reactions in either the positive or negative electrode.

[0057] The following is a reference. Figure 1 The structure of a square non-aqueous electrolyte secondary battery (lithium secondary battery, lithium-ion secondary battery) will be described as an example.

[0058] The battery comprises a square-bottomed battery casing 4, an electrode assembly 1 housed within the battery casing 4, and a non-aqueous electrolyte (not shown). The electrode assembly 1 has a long strip-shaped negative electrode, a long strip-shaped positive electrode, and a separator sandwiched between them. The negative electrode current collector is electrically connected to the negative terminal 6 disposed on the sealing plate 5 via a negative electrode lead 3. The negative terminal 6 is insulated from the sealing plate 5 by a resin gasket 7. The positive electrode current collector is electrically connected to the back of the sealing plate 5 via a positive electrode lead 2. That is, the positive electrode is electrically connected to the battery casing 4, which also serves as a positive terminal. The periphery of the sealing plate 5 is fitted into the open end of the battery casing 4, and the fitting is laser-welded. The sealing plate 5 has an injection hole for the non-aqueous electrolyte, which is blocked by a sealing plug 8 after electrolyte injection.

[0059] [negative electrode]

[0060] In the case of lithium-ion secondary batteries, where over 70% of the rated capacity is due to the deposition and dissolution of lithium metal, the negative electrode only needs to have a negative current collector. In the case of lithium-ion secondary batteries, the movement of electrons in the negative electrode during charging and discharging is primarily due to the deposition and dissolution of lithium metal. Specifically, 70-100% (e.g., 80-100%, 90-100%) of the movement of electrons (or, from another perspective, current) in the negative electrode during charging and discharging is due to the deposition and dissolution of lithium metal.

[0061] The negative electrode may have a negative current collector and a negative electrode additive layer loaded on the surface of the negative current collector. The negative electrode additive layer is formed by coating a negative electrode slurry containing a negative electrode additive dispersed in a dispersion medium onto the surface of the negative current collector and then drying it. The dried coating film can be calendered as needed. The negative electrode additive layer can be formed on one surface or on both surfaces of the negative current collector.

[0062] The negative electrode mixture may contain a negative electrode active material as an essential component, and may also contain binders, conductive agents, thickeners, etc., as optional components. The negative electrode active material may include the aforementioned negative electrode material (composite particles with a conductive layer).

[0063] Examples of anode active materials include materials with a graphitic crystal structure that can reversibly absorb, store, and release lithium ions, such as natural or artificial graphite, carbon materials such as hard carbon (difficult-to-graphitize carbon) and soft carbon (easily-graphitize carbon), Si-containing materials, and Sn-containing materials. The anode may contain one type of anode active material or a combination of two or more. Carbon materials and Si-containing materials are preferred among the anode active materials. A combination of carbon materials and Si-containing materials is also possible.

[0064] As the negative current collector, non-porous conductive substrates (such as metal foils) or porous conductive substrates (such as sieves, meshes, perforated sheets, etc.) can be used. Examples of materials for the negative current collector include stainless steel, nickel, nickel alloys, copper, and copper alloys. The thickness of the negative current collector is not particularly limited; from the viewpoint of balancing the strength and lightweight of the negative electrode, 1–50 μm is preferred, and more ideally, 5–20 μm.

[0065] As a negative electrode active material, known materials capable of absorbing, storing, and releasing lithium ions can be used, for example. Examples of negative electrode active materials include elemental lithium metal, lithium alloys, silicon, silicon alloys, graphite, non-graphitizable carbon, and lithium-containing metal oxides.

[0066] Examples of adhesives include resin materials such as fluoropolymers like polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF); polyolefin resins like polyethylene and polypropylene; polyamide resins like aromatic polyamide resins; polyimide resins like polyimide and polyamide-imide; acrylic resins like polyacrylic acid, polymethyl acrylate, and ethylene-acrylic acid copolymers; vinyl resins like polyacrylonitrile and polyvinyl acetate; polyvinylpyrrolidone; polyethersulfone; and rubber-like materials like styrene-butadiene copolymer rubber (SBR). An adhesive can be used alone or in combination of two or more types.

[0067] Examples of conductive agents include carbon-based conductive agents such as acetylene black; conductive fibers such as carbon fibers and metal fibers; fluorinated carbon; metal powders such as aluminum; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and organic conductive materials such as phenylene derivatives. A single conductive agent can be used, or two or more can be used in combination.

[0068] Examples of thickeners include carboxymethyl cellulose (CMC) and its modified forms (including salts such as Na salts), cellulose derivatives such as methyl cellulose (cellulose ethers, etc.); saponifications of polymers containing vinyl acetate units such as polyvinyl alcohol; and polyethers (polyethylene oxides, polyepoxides, etc.). A single thickener can be used alone, or in combination of two or more.

[0069] There are no particular limitations on the dispersion medium; for example, water, alcohols such as ethanol, ethers such as tetrahydrofuran, amides such as dimethylformamide, N-methyl-2-pyrrolidone (NMP), or mixtures thereof can be used.

[0070] [positive electrode]

[0071] The positive electrode can have a positive current collector and a positive electrode additive layer loaded on the surface of the positive current collector. The positive electrode additive layer is formed by coating a positive electrode slurry containing a positive electrode additive dispersed in a dispersion medium onto the surface of the positive current collector and then drying it. The dried coating can be calendered as needed. The positive electrode additive layer can be formed on one surface or on both surfaces of the positive current collector. The positive electrode additive can contain a positive electrode active material as a necessary component and can also contain binders, conductive agents, etc., as optional components. NMP or similar materials can be used as the dispersion medium for the positive electrode slurry.

[0072] As a positive electrode active material, lithium-containing composite oxides can be used, for example. Li can be cited as an example. a CoO2, Li a NiO2, Li a MnO2, Li a Co b Ni 1-b O2, Lia Co b Me 1-b O c 、 Li a Ni 1-b Me b O c 、 Li a Mn2O4, Li a Mn 2-b Me b O4, LiMePO4, Li2MePO4F (Me is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B). Here, a = 0 to 1.2, b = 0 to 0.9, c = 2.0 to 2.3. It should be noted that the value of a representing the molar ratio of lithium increases or decreases according to charge and discharge.

[0073] Among them, Li a Ni b Me 1-b O2 (Me is at least one selected from the group consisting of Mn, Co, and Al, 0 < a ≤ 1.2, 0.3 ≤ b ≤ 1) is shown as a lithium nickel composite oxide. From the viewpoint of high capacity, it is more preferably 0.85 ≤ b < 1. From the viewpoint of the stability of the crystal structure, it is further preferably Li a Ni b Co c Al d O2 (0 < a ≤ 1.2, 0.85 ≤ b < 1, 0 < c < 0.15, 0 < d ≤ 0.1, b + c + d = 1).

[0074] As the binder and the conductive agent, the same substances as those exemplified for the negative electrode can be used. As the conductive agent, graphite such as natural graphite and artificial graphite can be used.

[0075] The shape and thickness of the positive electrode current collector can be respectively selected from the shapes and ranges corresponding to the negative electrode current collector. As the material of the positive electrode current collector, for example, stainless steel, aluminum, aluminum alloy, titanium, etc. can be exemplified.

[0076] [Electrolyte solution]

[0077] The electrolyte solution contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. The concentration of the lithium salt in the electrolyte solution is preferably, for example, 0.5 mol / L or more and 2 mol / L or less. By making the lithium salt concentration within the above range, an electrolyte solution with excellent ion conductivity and moderate viscosity can be obtained. However, the lithium salt concentration is not limited to the above.

[0078] As a non-aqueous solvent, cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, and chain carboxylic acid esters can be used, for example. Examples of cyclic carbonates include propylene carbonate (PC) and ethylene carbonate (EC). Examples of chain carbonates include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). Examples of chain carboxylic acid esters include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate. One non-aqueous solvent can be used alone, or two or more can be used in combination.

[0079] Examples of lithium salts include LiClO4, LiBF4, LiPF6, LiAlCl4, LiSbF6, LiSCN, LiCF3SO3, LiCF3CO2, LiAsF6, and LiB. 10 Cl 10 Lower aliphatic carboxylic acids such as lithium, LiCl, LiBr, LiI, borates, and imide salts. Examples of borates include lithium dioxane borate, lithium difluorooxane borate, lithium bis(1,2-benzene diolate(2-)-O,O')borate, lithium bis(2,3-naphthalene diolate(2-)-O,O')borate, lithium bis(2,2'-biphenyl diolate(2-)-O,O')borate, and lithium bis(5-fluoro-2-olate-1-benzenesulfonic acid-O,O')borate. Examples of lithium bis(fluorosulfonyl)imide lithium (LiN(FSO2)2), lithium bis(trifluoromethanesulfonyl)imide lithium (LiN(CF3SO2)2), lithium trifluoromethanesulfonylnonafluorobutyrylimide lithium (LiN(CF3SO2)(C4F9SO2)), and lithium bis(pentafluoroethanesulfonyl)imide lithium (LiN(C2F5SO2)2). LiPF6 is preferred. A single lithium salt can be used alone, or in combination of two or more.

[0080] The present invention will be specifically described below based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0081] <Example 1>

[0082] [Preparation of LSP]

[0083] A reaction solution was prepared by mixing 1g of α-cellulose (a polysaccharide), 14mL of 1-propanol, and 4mL of a 10mol / L KOH aqueous solution, and stirring the reaction solution for 1 hour.

[0084] Add 3.904 g of sodium 2-bromoethylsulfonate (Br-CH2CH2-SO3Na) to the reaction solution, and then stir the reaction solution at 70°C for 70 hours. Replace some of the hydrogen atoms of the hydroxyl group of the raw organic polymer with potassium ethylsulfonate (or sodium ethylsulfonate) as shown in the formula: -CH2CH2SO3K (or -CH2CH2SO3Na).

[0085] Next, the cellulose (SEC-K) infused with potassium ethylsulfonate (or sodium ethylsulfonate) groups was filtered through a 0.1 μm pore size polytetrafluoroethylene membrane filter. It was then washed with a 70% (w / w) methanol aqueous solution, followed by another wash with methanol. The washed SEC-K was then allowed to air dry for 24 hours. Afterward, the SEC-K was vacuum dried at 105°C for 10 hours.

[0086] Next, the obtained SEC-K was dissolved in water to prepare an aqueous solution, which was then contacted with a strongly acidic ion exchange resin to obtain cellulose with sulfoethyl groups. Then, 1M of an aqueous solution of LiOH was added to the acidic sulfoethyl cellulose solution for neutralization, replacing the hydrogen atoms of the sulfoethyl group with Li, resulting in an LSP with lithium-ion conductivity, as an example, having the structure shown below.

[0087]

[0088] [Evaluation of Li ion conductivity]

[0089] An aqueous solution containing LSP was cast into a PFA-coated petri dish, allowing the water to evaporate from the coating, resulting in a 100 μm thick, non-porous, dense membrane. The resulting membrane (LSP membrane) was cut into a circle with a diameter of 12 mm and held between a pair of stainless steel electrodes. The ionic conductivity at 25 °C, 40 °C, and 60 °C was measured by AC impedance spectroscopy under conditions of 7 MHz–100 mMHz and 10 mV amplitude. The results are shown in Table 1.

[0090] [Table 1]

[0091] temperature Ionic conductivity (S / cm) 60℃ <![CDATA[7.1×10 -3 ]]> 40℃ <![CDATA[4.5×10 -3 ]]> 25℃ <![CDATA[2.9×10 -3 ]]>

[0092] The air permeability of the LSP membrane was measured using existing methods, and the result was above 10,000 seconds / 100 mL.

[0093] It should be noted that a non-porous dense cellulose membrane with a thickness of 17 μm was prepared separately, and the resulting membrane was cut into a circle with a diameter of 12 cm. The ionic conductivity was measured in the same manner as above, and the results confirmed that it had no ionic conductivity.

[0094] Industrial availability

[0095] The alkali metal ion-conducting solid electrolyte of the present invention is suitable as a material for non-aqueous electrolyte secondary batteries.

[0096] The novel features of the invention are set forth in the appended claims, but the invention, in terms of both its structure and content, along with its other objects and features, will be better understood from the following detailed description with reference to the accompanying drawings.

[0097] Explanation of reference numerals in the attached figures

[0098] 1: Electrode assembly; 2: Positive lead; 3: Negative lead; 4: Battery casing; 5: Sealing plate; 6: Negative terminal; 7: Gasket; 8: Sealing plug

Claims

1. An alkali metal ion-conducting solid electrolyte, comprising an organic polymer having sulfonic acid alkali metal salt groups, wherein, The mass (EW value) of the organic polymer in each mole of the sulfonic acid alkali metal salt is more than 168 g / mol and less than 300 g / mol, and the sulfonic acid alkali metal salt is a part of the alkyl sulfonic acid alkali metal salt represented by the formula: -R-SO3X, wherein R is an alkylene group and X is an alkali metal atom.

2. The alkali metal ion-conducting solid electrolyte according to claim 1, wherein, The organic polymer also has multiple hydroxyl groups.

3. The alkali metal ion-conducting solid electrolyte according to claim 1 or 2, wherein, The organic polymer is a derivative of polysaccharides.

4. The alkali metal ion-conducting solid electrolyte according to claim 1 or 2, wherein, The sulfonic acid alkali metal salt is a lithium sulfonic acid lithium salt where X is lithium.

5. A separator for a non-aqueous electrolyte secondary battery, comprising the alkali metal ion-conducting solid electrolyte as described in claim 1.

6. The separator for a non-aqueous electrolyte secondary battery according to claim 5, wherein the separator is non-porous.

7. A non-aqueous electrolyte secondary battery, comprising: positive electrode, negative electrode, The separator for a non-aqueous electrolyte secondary battery as described in claim 5, sandwiched between the positive and negative electrodes. The first electrolyte in contact with the positive electrode, and The second electrolyte in contact with the negative electrode, The composition of the first electrolyte is different from that of the second electrolyte.

8. A non-aqueous electrolyte secondary battery, comprising: positive electrode, negative electrode, The separator sandwiched between the positive and negative electrodes, and The electrolyte in contact with the positive and negative electrodes At least one of the positive electrode and the negative electrode comprises the alkali metal ion conductive solid electrolyte as described in claim 1.

9. A method for manufacturing an alkali metal ion-conducting solid electrolyte according to any one of claims 1 to 8, comprising the step of: adding a haloalkyl sulfonate to an alkaline liquid comprising a raw material organic polymer having a plurality of hydroxyl groups, wherein at least one hydrogen atom of said hydroxyl group is replaced with an alkyl sulfonate group of the formula: -R-SO3X, wherein... R stands for alkylene group, and X stands for alkali metal atom.

10. The method for manufacturing an alkali metal ion-conducting solid electrolyte according to claim 9, wherein, The haloalkyl sulfonate is a bromoalkyl sulfonate.

11. The method for manufacturing an alkali metal ion-conducting solid electrolyte according to claim 9 or 10, wherein, The alkali metal atom X is K or Na.

12. The method for manufacturing an alkali metal ion-conductive solid electrolyte according to claim 11, further comprising a step of ion-exchanging the alkali metal atom X into Li.

13. The method for manufacturing an alkali metal ion-conducting solid electrolyte according to claim 9 or 10, wherein, The alkaline liquid is a dispersion in which the raw material organic polymer is dispersed in an organic solvent.

14. A method for manufacturing a separator for a non-aqueous electrolyte secondary battery, comprising a step of molding the alkali metal ion-conducting solid electrolyte of claim 1 into a sheet shape.

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