Electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery, and method for producing electrode for non-aqueous electrolyte secondary battery

Abstract

The present invention provides an electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery that can suppress corrosion reactions of an aluminum current collecting layer and further suppress deterioration of battery capacity and output characteristics in an aqueous-based positive electrode manufacturing process. The electrode for a non-aqueous electrolyte secondary battery of the present invention is an electrode for a non-aqueous electrolyte secondary battery having an electrode mixture layer on an aluminum current collecting layer, the electrode mixture constituting the electrode mixture layer includes an active material, a binder, and a protective film forming agent, the active material being an active material capable of electrochemically occluding and desorbing alkali metal ions or an active material capable of electrochemically alloying and dealloying alkali metal ions, the protective film forming agent including an alkali silicate, and a protective film formed by the protective film forming agent being present on the surface of the aluminum current collecting layer.

Description

[Technical field]

[0001] The present invention relates to an electrode for a non-aqueous electrolyte secondary battery. 、 Non-aqueous electrolyte secondary battery and a method for producing an electrode for a non-aqueous electrolyte secondary battery Regarding. [Background technology]

[0002] As electrochemical devices to be installed in mobile phones, electric vehicles, etc., electric double layer capacitors, lithium ion secondary batteries, sodium ion secondary batteries, and other power storage devices have been developed. Among these, lithium ion secondary batteries enable devices to be made smaller and lighter, have good charge / discharge efficiency, and have high energy density, and are therefore used as power sources for, for example, mobile devices, notebook PCs, home appliances, and even hybrid and electric vehicles. In addition, lithium ion secondary batteries have been attracting new attention as power storage devices for storing generated electricity in combination with natural energy systems such as solar power generation and wind power generation.

[0003] The electrodes that make up a lithium-ion secondary battery are composed of an active material that absorbs and releases energy by absorbing and releasing lithium ions, a conductive assistant to ensure electrical conductivity within the electrode, a binder to bond the active material and conductive agent, a current collecting layer to connect to external circuits outside the battery, etc. The characteristics of a lithium-ion secondary battery are highly dependent on the electrodes, and are greatly affected by the characteristics of each material itself and how the materials are combined.

[0004] In recent years, the applications of lithium-ion secondary batteries have expanded, and the market is expanding not only for electric vehicles but also for stationary storage batteries for disaster prevention and power business use, and there is a growing demand for batteries that not only have higher performance but also lower costs. In particular, in order to reduce the cost of secondary batteries, it is necessary to review not only the materials used in battery production but also the battery manufacturing process, and many studies have been conducted so far.

[0005] For example, lithium transition metal oxides with a high nickel (Ni) content have been studied in recent years as a positive electrode active material for lithium-ion secondary batteries in order to increase the capacity. Increasing the capacity of the positive electrode active material improves the energy density per weight, and the amount of material used can be reduced, making it possible to reduce the cost of the battery. On the other hand, the electrodes are manufactured by forming a paint (slurry) from the above-mentioned active material, conductive agent, and binder using water or an organic solvent, and coating the positive electrode on an aluminum current collecting layer, and the negative electrode on a copper or aluminum current collecting layer. In this case, an organic solvent called N-methyl-N-pyrrolidone (NMP) is used to make the slurry for the positive electrode, and not only the cost of the organic solvent itself but also the cost of recovery and purification affect the final battery cost.

[0006] In response to these problems, attempts have been made to reduce costs by replacing organic solvents with water in the manufacture of positive electrodes. However, when the positive electrode active material is dispersed in water, lithium ions are dissolved from the active material into the water, and the pH of the slurry becomes a strong alkaline state of 10 or more. When such a slurry is applied to an aluminum current collecting layer, a corrosion reaction between the aluminum and hydroxide ions progresses, and hydrogen gas is generated from the aluminum surface. As a result, there is a problem that a smooth electrode cannot be obtained because hydrogen gas is mixed into the coating layer as bubbles. In addition, in such an electrode, the parts where the bubbles were mixed become voids after drying, and the electronic path in the electrode mixture layer is interrupted, which increases the battery resistance.

[0007] In order to overcome the above-mentioned problems, Patent Document 1 discusses adding a neutralizing agent to a high pH slurry to neutralize the pH to a level at which corrosion of the aluminum current collecting layer does not occur.

[0008] However, these techniques for controlling the slurry pH by neutralization reactions induce the elution of lithium ions from the positive electrode active material, which leads to a decrease in battery capacity. In addition, it is necessary to add a neutralizing agent to the electrode mixture at a weight ratio of 1% or more, which also contributes to a decrease in energy density. Therefore, the above-mentioned slurry pH control by neutralization reactions has not been sufficiently studied to switch from organic solvents to aqueous systems in the production of positive electrodes. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2016 / 052715 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the above problems, and an object of the present invention is to solve the problem of suppressing the corrosion reaction of the aluminum current collecting layer and further suppressing the deterioration of the battery capacity and output characteristics in the aqueous system production process of the positive electrode. [Means for solving the problem]

[0011] As a result of intensive research aimed at solving the above-mentioned problems, the inventors have discovered that by applying an aqueous slurry containing an alkali silicate to an aluminum current collecting layer, a protective film that is corrosion-resistant against high pH aqueous slurries can be formed on the aluminum current collecting layer, thereby suppressing deterioration of battery capacity and output characteristics, and have completed the present invention.

[0012] In order to achieve the above object, the present invention provides an electrode for a non-aqueous electrolyte secondary battery, comprising an electrode mixture layer on an aluminum current collecting layer, the electrode mixture slurry constituting the electrode mixture layer is an aqueous slurry containing an active material, a binder, a thickener, and a protective film forming agent; the active material is an active material capable of electrochemically absorbing and desorbing alkali metal ions, or an active material capable of electrochemically alloying and dealloying alkali metal ions, The protective film forming agent includes an alkali silicate, The ratio of the protective film forming agent to the solid content of the electrode mixture slurry is in the range of 0.2% by weight or more and 0.4% by weight or less, the electrode mixture slurry is prepared by mixing at least the active material, the thickener, and water, and then adding the protective film forming agent; The protective film formed by the protective film forming agent is present on the surface of the aluminum current collecting layer.

[0013] In the electrode for a nonaqueous electrolyte secondary battery of the present invention, it is preferable that the protective film forming agent contains at least an alkali silicate represented by MO·nSiO, where M contains at least one of Li, Na, and K, and n is 1.6 or more and 8.0 or less.

[0014] In the electrode for a non-aqueous electrolyte secondary battery of the present invention, the weight ratio of the protective film forming agent in the electrode mixture is preferably in the range of more than 0.1% and 1% or less.

[0015] In the electrode for a non-aqueous electrolyte secondary battery of the present invention, After peeling off the electrode mixture layer, The protective film on the surface of the aluminum current collecting layer was found to be Si2p 3 / 2 It is preferable that the spectrum contains at least a Si—O bond having a bond energy in the range of 102 to 107 eV.

[0016] In the electrode for a non-aqueous electrolyte secondary battery of the present invention, the aluminum current collecting layer is preferably made of pure aluminum or an alloy containing aluminum and one or more additive elements.

[0017] In the electrode for a non-aqueous electrolyte secondary battery of the present invention, the active material is Li x MO2, LiM2O4, Li4M5O 12 (x is 1 to 2, M is a transition metal), and a lithium oxide containing at least one transition metal; A lithium polyanion compound represented by LiMPO4 (M is a transition metal) and containing at least one transition metal, a lithium inorganic compound selected from a lithium sulfur compound, a lithium selenium compound, and a lithium fluoride compound; A sodium oxide represented by NaMO2 or Na2MO3 (M is a transition metal) containing at least one transition metal, A sodium polyanion compound containing at least one transition metal, represented by NaM2(XO4)3, NaMPO4 or NaM(SO4)2 (wherein M is a transition metal and X is one of sulfur, phosphorus and silicon), A sodium Prussian blue analogue represented by Na2M[M'(CN)6] (M, M' are transition metals) and containing at least one transition metal; It is preferable that the compound is at least one selected from the group consisting of:

[0018] The nonaqueous electrolyte secondary battery of the present invention includes a positive electrode and a negative electrode, the positive electrode and the negative electrode being separated by an insulating layer, and at least one of the positive electrode and the negative electrode being an electrode for the nonaqueous electrolyte secondary battery of the present invention. Effect of the Invention

[0019] According to the present invention, it is possible to manufacture electrodes in an aqueous process using positive and negative electrode active materials containing alkaline ions such as lithium and sodium while suppressing corrosion of the aluminum current collecting layer. In addition, even though the manufactured electrodes are produced in an aqueous process, the deterioration of the battery capacity and output characteristics can be suppressed. A non-aqueous electrolyte secondary battery using such electrodes can be provided at a lower cost than conventional batteries. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a set of photographs showing the results of visual observation of the surfaces of electrode mixture layers of (A) Comparative Example 2 and (B) Example 1, (C) Example 2, and (D) Example 3 produced based on the present invention. [Diagram 2]FIG. 2 is a set of photographs showing the results of visual observation of the surfaces of the electrode mixture layers of (E) Comparative Example 3, and (F) Example 4, (G) Example 5, and (H) Example 6 produced based on the present invention. [Diagram 3] FIG. 3 is a set of photographs showing the results of visual observation of the surfaces of the electrode mixture layers of (I) Comparative Example 4, and (J) Example 7, (K) Example 8, and (L) Example 9 produced based on the present invention. [Figure 4] FIG. 4 is a photograph showing the results of visual observation of the surface of the electrode mixture layer in Comparative Example 1 (M). [Diagram 5] FIG. 5 shows SEM images of the electrode mixture layer surfaces of (A) Comparative Example 2, (B) Example 1, (C) Example 2, and (D) Example 3. [Figure 6] FIG. 6 shows SEM images of the surfaces of the electrode mixture layers of (E) Comparative Example 3, (F) Example 4, (G) Example 5, and (H) Example 6. [Figure 7] FIG. 7 shows SEM images of the electrode mixture layer surfaces of (I) Comparative Example 4, (J) Example 7, (K) Example 8, and (L) Example 9. [Figure 8] FIG. 8 is an SEM image of the surface of the electrode mixture layer of Comparative Example 1 (M). [Figure 9] FIG. 9 shows the results of XPS measurement of the Si2p3 / 2 spectrum on the aluminum current collecting layer surface of Comparative Example 1, Comparative Example 2, Example 1, and Example 1 after charging and discharging, and of Example 2 and Example 3. [Figure 10] FIG. 10 shows the results of XPS measurement of the Si2p3 / 2 spectrum on the aluminum current collecting layer surface of Comparative Example 1, Comparative Example 3, Example 4, and Example 4 after charging and discharging, and of Example 5 and Example 6. [Figure 11] FIG. 11 shows the results of XPS measurement of the Si2p3 / 2 spectrum on the aluminum current collecting layer surface of Comparative Example 1, Comparative Example 4, Example 7, and Example 7 after charging and discharging, and of Example 8 and Example 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the embodiments of the present invention will be described in detail, but the scope of the present invention is not limited to these descriptions, and other than the following examples, the present invention can be appropriately modified and implemented without departing from the spirit of the present invention. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more, B or less." In addition, "mass" and "weight," "mass %" and "weight %" are treated as synonyms.

[0022] The positive and negative electrodes of the nonaqueous electrolyte secondary battery of the present invention contain a protective film forming agent, an active material capable of electrochemically absorbing and desorbing alkali ions or an active material capable of electrochemically alloying and dealloying alkali metal ions, and a binder. The protective film forming agent contains an alkali silicate and forms a protective film that suppresses corrosion reactions on the surface of the aluminum current collecting layer.

[0023] <Protective film forming agent> As the protective film forming agent, an alkali silicate represented by M2O·nSiO2 can be used. Here, M is Li, Na, or K. The alkali species may be used alone or in combination of two or more. When two or more types are used in combination, the combination and mixing ratio of the alkali species can be selected arbitrarily. Moreover, n is 1.6 or more and 8.0 or less, and preferably 2.5 or more and 7.5 or less. It is preferable to use an aqueous solution in which the alkali silicate is dissolved in water, and the weight ratio of the alkali silicate in the aqueous solution is 10 to 80%.

[0024] <Aluminum current collecting layer> As the material used for the aluminum current collecting layer, pure aluminum or an alloy containing aluminum and one or more additive elements can be used. As the pure aluminum, for example, materials such as A1050, A1070, A1085, A1100, A1235, 1N30, 1N90, and 1N99, which have an aluminum weight ratio of 99% or more as specified by the JIS standard, can be used. As the aluminum alloy, materials such as A3003, A3103, A3203, A3004, A3104, A3005, and A3105 of Al-Mn alloys and A8021 and A8079 of Al-Fe alloys can be used. As the form of the aluminum current collecting layer, rolled foil, punched foil, mesh, foam, and the like can be arbitrarily used, and the thickness is in the range of 1 μm to 2 mm. When using rolled foil, the thickness is preferably 5 to 20 μm. The aluminum current collecting layer may be surface-treated or coated with carbon, fluorine, tungsten, zirconium, or the like.

[0025] <Active material> The active materials capable of electrochemically absorbing and desorbing alkali ions or electrochemically alloying and de-alloying alkali ions are LiCoO2, LiMn 1-a Fe a PO4, LiNi 2-b Mn b O4, Li c Ni d Mn e Co f M 1-d-e-f Lithium oxides and lithium polyanion compounds represented by the formula (I) and (II) can be used. In the above, it is possible to use the lithium polyanion compounds even if the ratio of the constituent elements is slightly different from the ratio described in the example chemical formula. Here, M is one or more elements selected from the group consisting of Na, K, Al, Mg, Ti, Fe, V, Cr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, Zr, Ru, and La, 0≦a≦1.0 0≦b≦2.0 0.8≦c≦2.0 0 <d≦1.0 0≦e<1.0 0≦f<1.0 0 <d+e+f≦1.0 In addition, lithium sulfur compounds, lithium selenium compounds, lithium fluoride compounds, etc. can be used. Sodium oxide, sodium polyanion compounds, and sodium Prussian blue analogues can also be used.

[0026] For the negative electrode, Li4Ti5O 12 Lithium titanium oxides, such as the compound represented by the following formula, can be used. In addition, transition metal oxides, such as CuO, Cu2O, MnO2, MoO3, V2O5, CrO3, MoO3, Fe2O3, Ni2O3, and CoO3, can be used.

[0027] In addition, active materials doped with elements such as aluminum, boron, fluorine, chromium, zirconium, molybdenum, magnesium, sodium, and iron, and active material particles whose surfaces have been treated or coated with carbon, Al2O3, Li3PO4, LiNbO3, TiO2, SiO2, etc. can also be used.

[0028] The active material may be one of the above materials alone or two or more of them in combination. At least two materials selected from the materials usable for the positive electrode may be used for the positive electrode, and at least two materials selected from the materials usable for the negative electrode may be used for the negative electrode. The mixing ratio of the materials constituting the active material may be arbitrary.

[0029] The device used to mix multiple materials is not particularly limited, but for example, in the case of rotary mixers, a cylindrical mixer, a twin cylindrical mixer, a double cone mixer, a regular cube mixer, a hoe-shaped mixer, and in the case of fixed mixers, a spiral mixer, a ribbon mixer, a Muller mixer, a Helical flight mixer, a Pugmil mixer, a fluidization mixer, etc. can be used.

[0030] The active material is preferably in a particulate form, and in this case, the particle diameter is preferably about 100 nm to 50 μm, and more preferably in the range of 200 nm to 20 μm. If the particle diameter is less than 100 nm, it is likely to be difficult to disperse the slurry, and if the particle diameter exceeds 50 μm, the battery characteristics are likely to deteriorate.

[0031] In the nonaqueous electrolyte secondary battery of the present invention, at least one of the positive electrode and the negative electrode is the electrode of the present invention. When either the positive electrode or the negative electrode is not the electrode of the present invention, examples of the active material suitable for use in the electrode include graphite, non-graphitizable carbon, graphitizable carbon, and lithium.

[0032] <Binder> The positive and negative electrodes for the non-aqueous electrolyte secondary battery of the present invention are provided with a binder. The binder is preferably contained in the electrodes at a weight ratio of 0.1% to 20%. More preferably, the binder is contained at a weight ratio of 0.5% to 10%. If the weight ratio of the binder is low, the adhesive strength decreases and the battery life decreases. If the weight ratio is high, the battery resistance increases.

[0033] As the binder, an emulsion aqueous solution, a polymer aqueous solution, a polymer aqueous dispersion, etc. can be used. As the emulsion, a resin-based emulsion developed for battery applications such as a synthetic resin emulsion "polyacrylic acid copolymer resin emulsion", "conjugated diene polymer emulsion", and "fluorine-containing copolymer emulsion" can be preferably used, as the polymer aqueous solution, a "water-soluble polyacrylic acid copolymer", and as the polymer aqueous dispersion, a "fluorine-containing copolymer aqueous dispersion" can be preferably used.

[0034] The "polyacrylic acid copolymer resin emulsion" is an emulsion of a copolymer resin obtained by emulsion polymerization of an acrylic acid monomer and other reactive monomers in water. The other reactive monomers include vinylidene fluoride monomers, styrene monomers, ethylenically unsaturated monomers containing a nitrile group, such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, crotononitrile, α-ethylacrylonitrile, α-cyanoacrylate, vinylidene cyanide, fumaronitrile, and other α,β-unsaturated nitrile monomers, monofunctional monomers such as methacrylic acid and acrylic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, 1,2,3,6-tetrahydrophthalic acid, 3-methyl-1,2,3,6-tetrahydrophthalic acid, 4-methyl-1,2,3,6-tetrahydrophthalic acid, methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic acid, and the like. Examples of the other reactive monomers include ethylenically unsaturated monomers containing carboxylic acids, such as trihydrophthalic acid, exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic acid, and himic acid; anhydrides of the ethylenically unsaturated monomers containing carboxylic acids; saponification products of the anhydrides; ethylenically unsaturated monomers containing ketone groups, such as methyl vinyl ketone, ethyl vinyl ketone, isopropyl vinyl ketone, isobutyl vinyl ketone, t-butyl vinyl ketone, and hexyl vinyl ketone; ethylenically unsaturated monomers containing organic acid vinyl ester groups, such as vinyl acetate, vinyl propionate, vinyl butyrate, trimethyl vinyl acetate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, and vinyl stearate; and the like. One type of other reactive monomer may be used, or two or more types may be used in combination.

[0035] In addition, by substituting the terminals of the polyacrylic acid copolymer resin with a specific functional group, it is possible to obtain a modified product capable of reacting with a specific monomer, etc. Examples of the modified product include an epoxy modified product, a carboxy modified product, an isocyanate modified product, a hydrogen modified product, etc.

[0036] As the "conjugated diene polymer emulsion", an emulsion of styrene butadiene copolymer rubber can be suitably used. The emulsion of styrene butadiene copolymer rubber is a particle of a copolymer of styrene and butadiene, and has a copolymer component derived from styrene and a copolymer component derived from butadiene. The content of the copolymer component derived from styrene is preferably 50 to 80 mol % based on the total copolymer components constituting the styrene butadiene copolymer. The content of the copolymer component derived from butadiene is preferably 20 to 50 mol % based on the total copolymer components.

[0037] The styrene-butadiene copolymer may have other reactive monomers other than the copolymerization components derived from styrene and the copolymerization components derived from butadiene. As the other reactive monomers, for example, those mentioned above as components of the emulsion of the polyacrylic acid copolymer resin can be used.

[0038] When the styrene-butadiene copolymer has the other reactive monomer, the content of the other reactive monomer is preferably 1 to 30 mol% based on the total copolymerization components constituting the styrene-butadiene copolymer. The styrene-butadiene copolymer may be any of a random copolymer, a block copolymer, and a graft copolymer. The styrene-butadiene copolymer may be carboxy-modified.

[0039] The styrene-butadiene copolymer rubber emulsion is an emulsion of rubber particles obtained by emulsion polymerization of styrene monomer, butadiene monomer, and, if necessary, other reactive monomers in water, and is also sometimes called latex or synthetic rubber latex.

[0040] Instead of the styrene-butadiene copolymer rubber, butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), nitrile rubber (NBR), butyl rubber (IIR), ethylene propylene rubber (EPDM), natural rubber (NR), etc. can also be used.

[0041] The term "fluorine-containing copolymer" refers to a copolymer containing at least one type of fluorine-containing monomer in the molecule. Examples of the fluorine-containing copolymer include a copolymer of polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a polyvinylidene fluoride-hexafluoropropylene (PVdF-co-HFP), an ethylene-tetrafluoroethylene copolymer (ETFE), a polychlorotrifluoroethylene (PCTFE), a propylene-tetrafluoroethylene copolymer, and an ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0042] A "fluorine-containing copolymer emulsion" is an emulsion of a copolymer resin obtained by emulsion polymerization in water of one kind of fluorine-containing monomer and another reactive monomer, or two or more kinds of fluorine-containing monomers, etc. A "water dispersion of a fluorine-containing copolymer" is an aqueous solution of a copolymer resin obtained by copolymerizing one kind of fluorine-containing monomer and another reactive monomer, or two or more kinds of fluorine-containing monomers, etc., or a dispersion in which the copolymer resin is dispersed in water.

[0043] The other reactive monomers include PVA, hexafluoropropylene, ethylene, and propylene.

[0044] The content (solids concentration) of the polyacrylic acid copolymer resin, the styrene-butadiene copolymer rubber, or the fluorine-containing copolymer in the polyacrylic acid copolymer resin emulsion, the styrene-butadiene copolymer rubber emulsion, the fluorine-containing copolymer emulsion, or the fluorine-containing copolymer aqueous dispersion is preferably 0.1 to 80% by weight, more preferably 0.5 to 65% by weight.

[0045] The solid content of the binder is preferably 0.5 to 95% by mass, and more preferably 1.0 to 85% by mass. The solid content is the mass ratio of the binder to the mass of the aqueous solution containing the binder.

[0046] <Slurry (electrode mixture slurry)> The slurry (electrode mixture slurry) for producing the electrode for a non-aqueous electrolyte secondary battery of the present invention contains a protective film forming agent, an active material, and a binder, and uses water as a solvent.

[0047] When the active material used for the positive and negative electrodes is mixed with water to prepare a slurry, alkaline ions are eluted from the active material structure, forming lithium hydroxide in the aqueous solution, and the pH becomes 10 or more. If a binder is added to such a high pH slurry and applied to an aluminum current collecting layer, a corrosion reaction occurs on the surface of the aluminum current collecting layer, and a smooth electrode cannot be obtained. However, in an electrode containing the protective film forming agent of the present invention, a corrosion-resistant protective film is formed on the surface of the aluminum current collecting layer, making it possible to suppress the corrosion reaction despite the high pH slurry. Therefore, it is no longer necessary to prepare an electrode with a slurry using a conventional organic solvent, and therefore the recovery and recycling costs of the organic solvent and the cost of the solvent itself are unnecessary, and as a result, the battery cost can be reduced. In addition, in the case of production in a water system, the conventional means of neutralizing a high pH slurry to a pH level at which corrosion of the aluminum current collecting layer does not occur by adding a neutralizing agent induces alkaline ion elution from the active material by the neutralizing agent, which reduces the battery capacity. And, the appropriate amount of neutralizing agent to be added had to be adjusted depending on the type and amount of active material. However, the technology of the present invention in which a protective film is formed on the surface of the current collecting layer using a protective film forming agent contained in the electrode mixture has the advantage that the amount added can be made constant regardless of the type of active material, etc.

[0048] The slurry for producing the electrode for a non-aqueous electrolyte secondary battery of the present invention preferably has a total solid content of the active material, binder, protective film forming agent, etc., excluding water, of 50 to 95% by weight. If the water content is low, the slurry viscosity increases, causing variations in the coating thickness, etc. If the water content is high, the time required for drying increases, and the coating speed decreases.

[0049] The slurry can be prepared, for example, by the following two methods. [Method 1] The active material, water-soluble thickener, etc. are mixed in powder form, water is added, and the mixture is kneaded. Then, a protective film forming agent is added, and the mixture is kneaded further. Finally, a binder is added, and the mixture is kneaded. [Method 2] An aqueous solution containing a water-soluble thickener and a water-soluble polymer binder is prepared in advance at a predetermined weight percentage. Then, the active material is added to this aqueous solution and kneaded. Finally, a protective film forming agent is added and kneaded.

[0050] These methods allow the protective film forming agent to be dispersed in advance in the electrode mixture slurry. In addition, by uniformly dispersing the protective film forming agent, a protective film can be formed uniformly on the surface of the aluminum current collecting layer. Note that the silica component contained in the protective film forming agent does not contribute to the battery capacity, so that a small amount of addition is preferable in terms of energy density. Therefore, in order to uniformly disperse the protective film forming agent in the electrode mixture slurry and uniformly form a protective film on the surface of the aluminum current collecting layer while maintaining the battery performance, the weight ratio of the protective film forming agent in the electrode mixture is preferably in the range of more than 0.1% and 1% or less.

[0051] In the above, the mixing or kneading method may be, for example, a method using various grinders, mixers, stirrers, etc., or a method using ultrasonic waves. Specific examples include a processing method using shear force or collision such as a mixer, a high-speed rotating mixer, a shear mixer, a blender, an ultrasonic homogenizer, a high-pressure homogenizer, or a ball mill; and a method using a Waring blender, a flash mixer, or a turbulizer. These methods may also be used in appropriate combination.

[0052] The slurry may contain a conductive assistant to ensure conductivity. Addition of the conductive assistant leads to a reduction in the internal resistance of the battery. The conductive assistant is not particularly limited, and examples thereof include metals, carbon materials, conductive polymers, conductive glass, and the like. Among these, carbon materials are preferred, and examples thereof include nanocarbons such as carbon nanotubes, carbon nanofibers, carbon nanohorns, and fullerenes; acetylene black, furnace black, thermal black, channel black, ketjen black, vulcan, graphene, vapor-grown carbon fiber (VGCF), and graphite. More preferred are acetylene black, ketjen black, VGCF, and carbon nanotubes. The carbon nanotubes may be single-walled, double-walled, or multi-walled carbon nanotubes. The conductive assistant may be used alone or in combination of two or more kinds. The conductive assistant may be treated with an acid or alkali to improve hydrophilicity. In addition, there is no particular limit to the shape, size, or specific surface area of ​​the conductive assistant. Any one can be selected depending on the amount added.

[0053] The slurry may contain a thickener or the like to ensure dispersion and viscosity stability. Examples of the thickener include water-soluble polymers such as sodium carboxymethylcellulose, alginic acid, polyacrylic acid, guar gum, and xanthan gum. Among these, alkali metal salts and ammonium salts of carboxymethylcellulose, alginic acid, and polyacrylic acid are preferred because they have excellent dispersion and viscosity stability. These thickeners may be used alone or in combination of two or more.

[0054] The water used to prepare the slurry is not particularly limited, and any commonly used water can be used. For example, tap water, distilled water, ion-exchanged water, pure water, ultrapure water, etc. can be used. Among them, ion-exchanged water, pure water, and ultrapure water are preferred.

[0055] The water may contain an organic solvent (hydrophilic organic solvent) that is uniformly miscible with water. Examples of hydrophilic organic solvents include N-methyl-2-pyrrolidone; dimethyl sulfoxide; alcohols such as methanol, ethanol, 2-propanol (IPA), isopropanol, n-butanol, and t-butanol; ketones such as acetone and methyl ethyl ketone (MEK); ethers such as 1,4-dioxane and tetrahydrofuran (THF); N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetonitrile, and ethyl acetate. One or more types of hydrophilic organic solvents may be used. However, from the viewpoints of safety, environmental impact, and ease of handling, it is preferable to use only water without using an organic solvent.

[0056] The mixing ratio of water to the organic solvent may be appropriately determined taking into consideration the type of organic solvent, the affinity between water and the organic solvent, and the like.

[0057] The weight ratio of each component in the solid content of the slurry is preferably, for example, 74.0 to 99.3% active material, 0.5 to 10.0% binder, 0.001 to 1.0% protective film forming agent, 0.1 to 10.0% conductive assistant, and 0.1 to 5.0% thickener, when the total weight of the active material, binder, protective film forming agent, conductive assistant, and thickener is 100%.

[0058] <Method of manufacturing electrode for non-aqueous electrolyte secondary battery> The electrode for a non-aqueous electrolyte secondary battery of the present invention can be produced, for example, by applying the above-mentioned slurry to the surface of a current collector layer, drying, and press molding. This makes it possible to produce an electrode for a non-aqueous electrolyte secondary battery in which an electrode mixture layer exists on a current collector layer. The electrode mixture layer is the coating layer part of the electrode after the slurry is applied to a current collector layer such as a foil and dried, and is a combination of an active material, a binder, a protective film forming agent, a conductive assistant, and a thickener. Furthermore, the electrode produced by the present invention has a protective film formed on the surface of an aluminum current collector layer.

[0059] Examples of the coating method include a method using a knife coater, a comma coater, a die coater, etc. As the current collecting layer, a pure aluminum foil or an alloy foil made of aluminum and one or more metals can be used.

[0060] The amount of the slurry applied to the current collecting layer can be set, for example, so that the thickness of the electrode mixture layer after drying is in the range of 0.01 to 0.40 mm, preferably 0.02 to 0.25 mm.

[0061] The temperature in the drying step can be appropriately set within the range of, for example, 35 to 150° C., preferably 40 to 135° C. The drying method can be selected from hot air drying, air blowing drying, infrared drying, reduced pressure drying, hot plate drying, etc. In the case of reduced pressure drying, the temperature can be set arbitrarily within the above range.

[0062] The thus obtained electrodes for a non-aqueous electrolyte secondary battery may be used as the positive electrode and negative electrode of the secondary battery.

[0063] <Non-aqueous electrolyte secondary battery electrode> The obtained electrode for a non-aqueous electrolyte secondary battery has the following characteristics. A corrosion-resistant protective film is formed on the surface of the aluminum current collecting layer by the alkali silicate, which is a protective film forming agent, and the electrode mixture layer containing the active material and binder is a smooth electrode without pore defects of 50 μm or more. With such an electrode, a battery with excellent output characteristics can be obtained, even if the electrode is made from an aqueous slurry.

[0064] As a reason for such improvement in output characteristics, it is considered that the protective film-forming agent forms a corrosion-resistant protective film on the surface of the aluminum current collector layer, thereby suppressing the corrosion reaction during electrode fabrication. In an electrode that does not contain a protective film-forming agent, since no protective film is formed on the surface of the aluminum current collector layer, when a slurry with a high pH is applied, a corrosion reaction occurs on the surface of the aluminum current collector layer. The hydrogen gas generated along with the corrosion reaction diffuses into the electrode mixture layer, and after drying, the portions where the hydrogen gas was present become void defects. Such voids cut off the electronic connection between the active materials in the electrode mixture, resulting in an increase in resistance. In the electrode according to the present invention, since the corrosion reaction can be suppressed by the protective film, excellent output characteristics can be obtained.

[0065] <Protective film> The protective film on the surface of the aluminum current collector layer of the electrode for a non-aqueous electrolyte secondary battery obtained by the present invention is characterized by having an Si-O bond. Further, since the protective film having an Si-O bond is water-insoluble, it effectively protects the surface of the aluminum current collector layer and suppresses the corrosion of aluminum by a high-pH slurry. Furthermore, when applied as an electrode of a non-aqueous electrolyte secondary battery, the protective film must be stably present with respect to the charge-discharge reaction. To determine whether the electrode has a protective film and whether there are no void defects of 50 μm or more in the electrode mixture layer, analysis by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) can be used. If a clear Si-O bond cannot be obtained by XPS, void defects of 50 μm or more due to the corrosion reaction are formed in the electrode mixture layer, the smoothness of the electrode is impaired, and the output characteristics of the battery deteriorate.

[0066] <XPS measurement> Measurement of the protective film on the surface of the aluminum current collector layer by XPS is performed using an X-ray photoelectron spectrometer. As a sample for measurement, the mixture layer of the fabricated electrode is peeled off with pure water, and the remaining aluminum current collector layer is used. MgKα rays are used as the XPS light source, and the Si2p 3 / 2 spectrum is analyzed.

[0067] The presence or absence of the protective film having an Si—O bond can be determined by whether a distinct peak is detected in the range of 102 to 107 eV in the XPS measurement.

[0068] <SEM Observation> The surface observation of the electrode mixture layer by SEM is performed using a scanning electron microscope. As the sample for observation, the fabricated electrode is used as it is. The presence or absence of pores with a size of 50 μm or more in the electrode mixture layer formed by the corrosion reaction can be determined by observing the surface of the mixture.

[0069] <Non-aqueous Electrolyte Secondary Battery> The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode and a negative electrode, and is a secondary battery including an electrolyte between the positive electrode and the negative electrode, wherein at least one of the positive electrode and the negative electrode is the electrode of the present invention.

[0070] In the non-aqueous electrolyte secondary battery, a separator is disposed between the positive electrode and the negative electrode in order to prevent short circuit between the positive electrode and the negative electrode. The current collector layers of the positive electrode and the negative electrode are connected to external devices. Charging and discharging are switched by operating this device.

[0071] Examples of the non-aqueous electrolyte secondary battery include a lithium ion secondary battery, a lithium ion capacitor, a sodium ion secondary battery, a sodium ion capacitor, and further include secondary batteries other than these.

[0072] The non-aqueous electrolyte secondary battery is a high-performance and highly safe power storage device, and thus the secondary battery may be mounted on small electronic devices such as mobile phones, notebook personal computers, portable information terminals, video cameras, digital cameras, mobile devices (vehicles) such as electric bicycles, electric automobiles, trains, power generation devices such as thermal power generation, wind power generation, hydraulic power generation, nuclear power generation, geothermal power generation, and natural energy power storage systems.

[0073] The non-aqueous electrolyte secondary battery of the present invention is preferably a lithium ion secondary battery, and the positive or negative electrode active material used in the secondary battery contains lithium in the active material structure.

[0074] The nonaqueous electrolyte secondary battery of the present invention includes the electrode of the present invention, and therefore exhibits particularly high battery characteristics, such as high battery capacity and high output characteristics, compared with nonaqueous electrolyte secondary batteries including electrodes obtained from conventional aqueous slurries that do not include a protective film-forming agent.

[0075] In the nonaqueous electrolyte secondary battery of the present invention, either the positive electrode or the negative electrode may be the electrode of the present invention, and if one of the positive electrode or the negative electrode is the electrode of the present invention, the other electrode may be produced from an aqueous slurry or an organic solvent slurry.

[0076] The nonaqueous electrolyte secondary battery of the present invention may be in the form of, for example, a cylindrical type in which a rectangular electrode and a separator are stacked and wound into a wound shape, a laminate type in which an electrode is wrapped in a separator and stacked and packaged in an aluminum laminate pouch, a coin type in which an electrode pellet and a separator are stacked, etc. A stainless steel case, an aluminum case, etc., is used as the exterior case.

[0077] <Electrolyte> As the electrolyte, lithium salts or lithium inorganic compounds having lithium ion conductivity are used. Lithium salts soluble in non-aqueous solvents can be used in the form of electrolytic solutions or gel-like, rubber-like, or sheet-like polymer electrolytes prepared by mixing with organic polymers. When using lithium inorganic compounds as the electrolyte, they can be used by forming them with a pressure press or a binder.

[0078] <Non-aqueous solvent> Examples of non-aqueous solvents used in the non-aqueous electrolyte solution include cyclic carbonates such as propylene carbonate, ethylene carbonate, vinylene carbonate, and butylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate; cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, and 3-dioxolane; chain ethers such as diethoxyethane and dimethoxyethane; sulfone solvents such as sulfolane, ethyl isopropyl sulfone, dimethyl sulfone, and di-normal propyl sulfone; chain esters such as methyl formate, methyl acetate, and methyl propionate; cyclic esters such as γ-butyrolactone and γ-valerolactone; and acetonitrile.

[0079] These non-aqueous solvents may be used alone or in combination of two or more. In the case of a mixed solvent, a combination of a cyclic carbonate and a chain carbonate is preferred. The cyclic carbonate dissolves lithium salts at a high concentration, and the chain carbonate can reduce the viscosity of the electrolyte without reducing the solubility of the lithium salt, so that a combination of these can provide an electrolyte with high ionic conductivity. In addition, these mixed solvents are also preferred in that they have high oxidation-reduction resistance and are less likely to be electrolyzed continuously within the operating voltage range of a lithium-ion battery.

[0080] The non-aqueous solvent used in the non-aqueous electrolyte may be an ionic liquid. An ionic liquid is a molten salt formed by combining a cation and an anion, and means a salt that exists in a liquid state in a wide temperature range including room temperature. The ionic liquid can be formed by appropriately combining at least one of the following cations and at least one of the following anions.

[0081] The cation of this ionic liquid is not particularly limited as long as it enables the movement of lithium ions in the electrolyte and enables charging and discharging of the electricity storage device, and examples thereof include imidazolium, pyridinium, pyrrolidinium, piperidinium, tetraalkylammonium, pyrazolium, and tetraalkylphosphonium.

[0082] The imidazolium may, for example, be 1-ethyl-3-methylimidazolium [EMIm + ], 1-butyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-allyl-3-methylimidazolium, 1-allyl-3-ethylimidazolium, 1-allyl-3-butylimidazolium and 1,3-diallylimidazolium.

[0083] Examples of the pyridinium include 1-propylpyridinium, 1-butylpyridinium, 1-allylpyridinium, 1-ethyl-3-(hydroxymethyl)pyridinium, and 1-ethyl-3-methylpyridinium.

[0084] The pyrrolidinium may be, for example, N-methyl-N-propylpyrrolidinium [MPPyr + ], N-methyl-N-butylpyrrolidinium, N-methyl-N-methoxymethylpyrrolidinium, N-allyl-N-methylpyrrolidinium, and N-allyl-N-propylpyrrolidinium.

[0085] Examples of the piperidinium include N-methyl-N-propylpiperidinium, N-methyl-N-butylpiperidinium, N-methyl-N-methoxymethylpiperidinium, and N-allyl-N-propylpiperidinium.

[0086] Examples of the tetraalkylammonium include N,N,N-trimethyl-N-propylammonium and methyltrioctylammonium.

[0087] Examples of the pyrazolium include 1-ethyl-2,3,5-trimethylpyrazolium, 1-propyl-2,3,5-trimethylpyrazolium, 1-butyl-2,3,5-trimethylpyrazolium, and 1-allyl-2,3,5-trimethylpyrazolium.

[0088] Examples of the tetraalkylphosphonium include P-butyl-P,P,P-triethylphosphonium and P,P,P-triethyl-P-(2-methoxyethyl)phosphonium.

[0089] The anion that is combined with these cations to form the ionic liquid may be any anion that allows the movement of lithium ions in the electrolyte and enables charging and discharging of the power storage device. For example, BF4 - , PF6 - , SbF6 - , NO3 - , CF3SO3 - , (FSO2)2N - [Bis(fluorosulfonyl)imide anion; FSI - ], (CF3SO2)2N - [Bis(trifluoromethylsulfonyl)imide; TFSI - ], (C2F5SO2)2N - , (CF3SO2)3C - , CF3CO2 - , C3F7CO2 - , CH3CO2 - , (CN)2N - These anions may include two or more kinds.

[0090] The lithium salt used in the non-aqueous electrolyte is not particularly limited, and examples thereof include fluoride-based lithium salts such as LiPF6, LiBF4, and LiAsF6, halide-based lithium salts such as LiClO4, LiCl, LiBr, and LiI, and sulfonate-based lithium salts such as LiN(CF3SO2)2 (LiTFSI) and LiN(FSO2)2 (LiFSI). The lithium salt may be used alone or in a mixture of two or more kinds. The concentration of the lithium salt in the non-aqueous electrolyte is 0.3 to 2.5 mol / dm 3 It is.

[0091] When the nonaqueous electrolyte solution is mixed with an organic polymer compound and used as a gel-like, rubber-like, or solid sheet-like electrolyte, examples of the organic polymer compound that can be used include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile, and PVDF-HFP.

[0092] The non-aqueous electrolyte may contain an additive to suppress continuous oxidation-reduction decomposition on the positive and negative electrodes. Examples of the additive include vinylene carbonate, fluoroethylene carbonate, ethylene sulfide, 1,3-propane sultone, 1,3-propene sultone, lithium bisoxalate borate, and lithium difluorooxalate borate. The content of the additive is preferably in the range of 10 to 0.1% by weight relative to the non-aqueous electrolyte. If the content is too high, it is undesirable because it leads to an increase in the resistance of the secondary battery. These additives have the function of forming a coating on the electrodes to protect the electrode surfaces, and the protective effect of this additive reduces the continuous oxidation-reduction decomposition reaction of the electrolyte on each electrode, and is effective in improving the life.

[0093] <Separator> In the non-aqueous electrolyte secondary battery of the present invention, a separator is provided between the positive electrode and the negative electrode to prevent short circuit between them. Examples of the separator include porous films containing polyethylene, polypropylene, cellulose, polyvinylidene fluoride (PVDF), polyimide, alumina, silica, etc. To form the porous film, holes can be provided by stretching a polymer film, or a fiber or granular polymer or inorganic compound can be molded using a press or a binder. A coating layer may be provided on one or both sides of the separator. The coating layer is a layer of several nm to several μm made of alumina, zirconia, silica, aramid, PVDF, etc., and is effective in preventing short circuit due to improved heat resistance and strength. EXAMPLES

[0094] The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited thereto.

[0095] <Production of positive electrode slurry using water as a solvent> The positive electrode active material was 94.8 to 95.2% by weight, the conductive additive was 2% by weight of carbon black, the protective film forming agent was 0.0 to 0.4% by weight of lithium silicate, the thickener was 0.55% by weight of carboxymethylcellulose Na (CMC-Na), and the binder was 2.25% by weight of acrylic emulsion. The slurry was prepared by mixing these materials using water as the solvent. The positive electrode active material was LiNi 0.8 Mn 0.1 Co 0.1 O2 was used. The protective film forming agent, lithium silicate, is expressed by the chemical formula Li2O·nSiO2, and three types of n were used: 3.5, 4.5, and 7.5. The detailed weight composition of the electrode mixture is shown in Table 1.

[0096] <Measurement of pH of electrode slurry> The pH of the resulting electrode slurry was measured by immersing a pH meter in the slurry for 10 minutes. The results are shown in Table 1.

[0097] <Preparation of electrodes using electrode slurry> The obtained electrode slurry was applied to one side of a 15 μm thick pure aluminum foil (material A1085) so that the active material coverage was 20.0 mg / cm 2 The electrode was then prepared by applying the mixture by a doctor blade method so that the positive electrode mixture density became 3.4 g / cc. The dried electrode was then pressed by a roll press machine so that the positive electrode mixture density became 3.4 g / cc.

[0098] <Evaluation of electrode corrosion state> To evaluate the corrosion state of the electrode obtained above, the surface of the electrode mixture layer was observed visually and with an SEM (Hitachi High-Tech, FlexSEM 1000II). SEM observation was performed at 100x magnification. Photographs showing the results of visual observation are shown in Figures 1 to 4, and SEM observation images are shown in Figures 5 to 8. The presence or absence of corrosion was evaluated according to the following criteria.

[0099] Corrosion present: There is one or more void defects with a diameter of 50 μm or more on the surface of the electrode mixture layer in the SEM observation area, or the aluminum current collecting layer is exposed when visually inspected from the surface of the electrode mixture layer. No corrosion: There are no pore defects with a diameter of 50 μm or more on the surface of the electrode mixture layer in the observation area, and there is no exposed aluminum current collecting layer when visually confirmed from the surface of the electrode mixture layer.

[0100] The results are shown in Table 2. In Comparative Examples 1 to 4 ((M), (A), (E), and (I) in the figure), hydrogen gas generation accompanying the aluminum corrosion reaction caused pore defects to form in the electrode mixture and exposed aluminum current collecting layer. In Examples 1 to 9, no pore defects or exposed aluminum current collecting layer were found in the electrode mixture, and smooth electrodes were obtained.

[0101] <Evaluation of the presence of protective film components on the surface of the aluminum current collecting layer> In order to evaluate the presence of components having Si-O bonds originating from the protective film forming agent on the surface of the aluminum current collecting layer of the electrode obtained above, analysis was performed using an XPS (JEOL, JPS-9010MC) MgKα radiation source. The composite layer of the electrode prepared above was peeled off with pure water to prepare a sample. The electrode for which the battery capacity and output characteristics were evaluated was taken out by dismantling and disassembling from the lithium ion battery described later, and the electrode composite layer was peeled off with pure water in the same manner as above to prepare a sample. The presence or absence of components originating from the protective film forming agent was evaluated using the Si2p 3 / 2 The spectra were evaluated based on the presence or absence of bond peaks in the range of 102-107 eV.

[0102] The results are shown in Table 2 and Figures 9 to 11. In Examples 1 to 9, the results of XPS measurement showed that bond peaks were clearly observed in the aforementioned range of 102 to 107 eV, and the presence of components having Si-O bonds was confirmed. On the other hand, in Comparative Examples 1 to 4, the corresponding bond peaks were scarce or absent, so it cannot be said that the components were sufficiently present on the aluminum current collecting layer, and this, together with the results of SEM observation and visual observation, supports the fact that the formation of a protective film was insufficient or absent.

[0103] <Evaluation of battery capacity and output characteristics> The non-aqueous electrolyte secondary battery electrode obtained above was used as the positive electrode of the battery to fabricate a lithium ion secondary battery having the following configuration. The positive electrode was processed to a size of 12 mmΦ, and the negative electrode was processed to a size of 13 mmΦ. Using these electrodes, a CR2032 type coin cell was fabricated in an argon atmosphere with a dew point of -60°C. The materials used are as follows:

[0104] Positive electrode: positive electrode for the non-aqueous electrolyte Anode: Lithium metal Electrolyte: The electrolyte was 1.0M LiPF6 dissolved in a non-aqueous solvent, ethylene carbonate (EC) and dimethyl carbonate (DMC), mixed in a volume ratio of 3:7. (Hereinafter referred to as 1.0M LiPF6 / EC:DMC [3:7 volume ratio].) Separator: Polyethylene porous film

[0105] [Measurement conditions] The battery capacity and output characteristics of the lithium ion secondary battery prepared above were evaluated by the following method. First, an evaluation sample was placed in a 25°C thermostatic chamber, and charged at a constant current up to 4.3V at a 10-hour rate (0.1C) current value, and constant voltage charging was performed to hold the voltage after the battery voltage reached 4.3V. The constant voltage charging was performed until the current value attenuated to 0.01C. Thereafter, constant current discharge was performed at a current value of 0.1C or 3C, and each capacity was measured when the battery voltage reached 3.0V. Here, the capacity obtained at a current of 0.1C was the battery capacity, and the capacity obtained at a current of 3C was the battery capacity obtained in the output test. The capacity retention rate was calculated by comparing the value of the 3C capacity with the 0.1C capacity. The battery capacity was calculated by dividing the actual capacity value (mAh) obtained by dividing the amount of positive electrode active material (g). The results are shown in Table 2.

[0106] [Table 1]

[0107] [Table 2]

[0108] As shown in Tables 1 and 2 and Figures 1 to 11, in Examples 1 to 3, Examples 4 to 6, and Examples 7 to 9, which contained 0.2 wt%, 0.3 wt%, and 0.4 wt% lithium silicate as a protective film forming agent, respectively, a protective film was formed on the surface of the aluminum current collecting layer of the electrode, and the corrosion reaction was suppressed even if an electrode was produced by applying an electrode slurry with a high pH of more than pH 11 to the aluminum current collecting layer. 3 / 2As shown in the results of the XPS measurement of the spectrum, in Examples 1 to 3, Examples 4 to 6, and Examples 7 to 9, the peaks derived from the Si-O bond were clearly observed in the range of 102 to 107 eV, and it was confirmed that a protective film was formed on the surface of the aluminum current collecting layer. In Figs. 9 to 11, the XPS measurement results of the aluminum current collecting layer surface after charging and discharging are further shown for Examples 1, 4, and 7. In these Examples, the Si-O bond peaks were clearly observed even after charging and discharging, and it was confirmed that the protective film was stable against the charging and discharging reaction. On the other hand, it was confirmed that a corrosion reaction occurred in Comparative Example 1, which does not include a protective film forming agent. In Comparative Examples 2, 3, and 4, in which the amount of the protective film forming agent is 0.1 wt%, the corrosion was reduced compared to Comparative Example 1, but the corrosion reaction occurred, and it was confirmed that the protective film formation was insufficient. As shown in Table 2, by using an electrode mixture containing a protective film forming agent, the electrode of the present invention having a protective film maintains electronic connection within the electrode mixture by suppressing or reducing the corrosion reaction, making it possible to obtain higher battery capacity and output characteristics than the comparative example.

[0109] From the above examples, it has been shown that the electrode mixture slurry prepared using the lithium oxide or the like according to the present invention as an active material and water as a solvent contains a protective film forming agent, and a protective film is formed on the surface of the aluminum current collecting layer, making it possible to suppress corrosion of the aluminum current collecting layer during electrode preparation, and the resulting electrode has high battery capacity and output characteristics. The present invention makes it possible to change from the conventional electrode preparation process using an organic solvent to an electrode preparation process using water, and therefore it is expected to reduce the cost of secondary battery electrodes and, ultimately, secondary batteries.

[0110] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

Claims

1. An electrode for a non-aqueous electrolyte secondary battery, comprising an electrode mixture layer on an aluminum current collecting layer, the electrode mixture slurry constituting the electrode mixture layer is an aqueous slurry containing an active material, a binder, a thickener, and a protective film forming agent; the active material is an active material capable of electrochemically absorbing and desorbing alkali metal ions, or an active material capable of electrochemically alloying and dealloying alkali metal ions, The protective film forming agent includes an alkali silicate, the electrode mixture slurry is prepared by mixing at least the active material, the thickener, and water, and then adding the protective film forming agent; a protective film formed by the protective film forming agent on a surface of the aluminum current collecting layer;

2. The protective film forming agent is M ２ O.nSiO ２ 2. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, comprising at least an alkali silicate represented by the formula: wherein M comprises at least one of Li, Na and K, and n is 1.6 or more and 8.0 or less.

3. 2 . The electrode for a non-aqueous electrolyte secondary battery according to claim 1 , wherein a weight ratio of the protective film forming agent in the electrode mixture is in the range of more than 0.1% and not more than 1%.

4. An electrode for a non-aqueous electrolyte secondary battery as described in claim 1, wherein the protective film forming agent is added as an aqueous solution.

5. After peeling off the electrode mixture layer, the protective film present on the surface of the aluminum current collecting layer is found to be Si2p by analysis using an X-ray source of MgKα rays by X-ray photoelectron spectroscopy (XPS). ３／２ 2. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, which contains at least a Si--O bond having a bond energy in the range of 102 to 107 eV in the spectrum.

6. 2. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the aluminum current collecting layer is made of pure aluminum or an alloy containing aluminum and one or more additive elements.

7. The active material is Li ｘ M.O. ２ , LiM ２ O ４ , Li ４ M ５ O １２ (x is 1 to 2, M is a transition metal), and a lithium oxide containing at least one transition metal; LiMPO ４ (M is a transition metal), and a lithium polyanion compound containing at least one transition metal; a lithium inorganic compound selected from a lithium sulfur compound, a lithium selenium compound, and a lithium fluoride compound; NaM.O. ２ or Na ２ M.O. ３ (M is a transition metal), and a sodium oxide containing at least one transition metal; NaM ２ (X.O. ４ ) ３ , NaMPO ４ or NaM(SO ４ ) ２ (M is a transition metal, and X is one of sulfur, phosphorus, and silicon), and a sodium polyanion compound containing at least one transition metal; Na ２ M [M' (CN) ６ ] (M and M' are transition metals), and a sodium Prussian blue analogue compound containing at least one transition metal; 2. The electrode for a non-aqueous electrolyte secondary battery according to claim 1, which is at least one selected from the following:

8. An electrode for a non-aqueous electrolyte secondary battery as described in claim 1, wherein the protective film forming agent contains lithium silicate represented by Li2O.nSiO2, where n is 3.5 or more and 7.5 or less, and the ratio of the protective film forming agent in the solid content of the electrode mixture slurry is in the range of 0.2 weight % or more and 0.4 weight % or less.

9. 9. A non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode, the positive electrode and the negative electrode being separated by an insulating layer, and at least one of the positive electrode and the negative electrode being the electrode for a non-aqueous electrolyte secondary battery according to claim 1.

10. A method for producing an electrode for a nonaqueous electrolyte secondary battery, comprising the steps of: As the electrode mixture slurry constituting the electrode mixture layer, an aqueous slurry containing an active material, a binder, a thickener and a protective film forming agent is used, the active material is an active material capable of electrochemically absorbing and desorbing alkali metal ions, or an active material capable of electrochemically alloying and dealloying alkali metal ions, The protective film forming agent includes an alkali silicate, The electrode mixture slurry is prepared by mixing at least the active material, the thickener, and water, and then adding the protective film forming agent; a method for manufacturing an electrode for a nonaqueous electrolyte secondary battery, comprising applying the electrode mixture slurry to a surface of the aluminum current collecting layer and drying the applied electrode mixture slurry to form a protective film on the surface of the aluminum current collecting layer using the protective film forming agent.

11. The method for manufacturing an electrode for a non-aqueous electrolyte secondary battery as described in claim 10, wherein the protective film forming agent contains at least an alkali silicate represented by M 2 O.nSiO 2 , wherein M includes at least one of Li, Na and K, and n is 1.6 or more and 8.0 or less.

12. A method for manufacturing an electrode for a non-aqueous electrolyte secondary battery as described in claim 10, wherein the ratio of the protective film forming agent to the solid content of the electrode mixture slurry is in the range of more than 0.1 weight % and not more than 1 weight %.

13. The method for producing an electrode for a non-aqueous electrolyte secondary battery according to claim 10, wherein the protective film forming agent is added as an aqueous solution.

14. A method for manufacturing an electrode for a non-aqueous electrolyte secondary battery as described in claim 10, wherein the protective film forming agent contains lithium silicate represented by Li2O.nSiO2, where n is 3.5 or more and 7.5 or less, and the ratio of the protective film forming agent in the solid content of the electrode mixture slurry is in the range of 0.2% or more and 0.4% or less.

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