Electrode composition, method for producing electrode composition, method for producing electrode sheet, and method for producing battery

Abstract

An electrode composition according to the present disclosure includes: a solvent; a coated active material that is dispersed in the solvent; and a binder that is dispersed in the solvent. The coated active material has an active material and a coating layer that covers at least a part of the surface of the active material. The coating layer contains a first solid electrolyte. The first solid electrolyte contains at least one substance that is selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte. The binder contains a styrene-based elastomer, and the total nitrogen content in the styrene-based elastomer is 30 ppm to 300 ppm inclusive.

Description

Electrode composition, method for manufacturing electrode composition, method for manufacturing electrode sheet, and method for manufacturing battery

[0001] The present disclosure relates to an electrode composition, a method for manufacturing an electrode composition, a method for manufacturing an electrode sheet, and a method for manufacturing a battery.

[0002] Patent Document 1 describes an electrode composition containing an active material and a modified styrene-based elastomer.

[0003] International Publication No. 2012 / 073678

[0004] In the manufacture of electrodes, a technique for improving the flowability of electrode compositions is desired.

[0005] The present disclosure aims to provide an electrode composition with improved flowability.

[0006] An electrode composition in one aspect of the present disclosure comprises: a solvent; a coated active material dispersed in the solvent; and a binder dispersed in the solvent, wherein the coated active material has an active material and a coating layer that coats at least a portion of a surface of the active material, the coating layer including a first solid electrolyte, the first solid electrolyte including at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte, the binder including a styrene-based elastomer, and a total nitrogen content of the styrene-based elastomer being 30 ppm or more and 300 ppm or less.

[0007] According to the present disclosure, an electrode composition with improved flowability can be provided.

[0008] FIG. 1 is a schematic diagram of an electrode composition in embodiment 1. FIG. 2 is a graph illustrating a method for evaluating the fluidity of an electrode composition. FIG. 3 is a schematic diagram of an electrode composition in a modified embodiment of embodiment 1. FIG. 4 is a flowchart showing a method for manufacturing an electrode sheet in embodiment 2. FIG. 5 is a cross-sectional view of an electrode in embodiment 2. FIG. 6 is a cross-sectional view of an electrode in embodiment 2. FIG. 7 is a cross-sectional view of a battery precursor in embodiment 2. FIG. 8 is a cross-sectional view of a battery in embodiment 3. FIG. 9 is a graph in which the viscosity obtained in the evaluation of the fluidity of the electrode composition in the examples and comparative examples is plotted against the shear rate. FIG. 10 is a graph in which the viscosity obtained in the evaluation of the fluidity of the electrode composition in the examples and comparative examples is plotted against the shear rate.

[0009] (Findings that Form the Basis of the Present Disclosure) To manufacture batteries such as nonaqueous electrolyte secondary batteries and solid state secondary batteries, it is necessary to prepare an electrode composition that contains an active material, a solvent, and a binder and has fluidity. For example, by using an electrode composition that has fluidity, an electrode sheet can be formed by applying the electrode composition to the surface of a current collector or the like. In the manufacture of electrode sheets, the use of an electrode composition enables production by wet coating. Wet coating is superior in terms of coating uniformity and mass productivity compared to dry coating.

[0010] Active materials and / or solid electrolytes are sensitive to the polarity of the solvent and the binder. To produce an electrode composition that is less likely to cause a decrease in battery output characteristics and cycle performance, it is necessary to use a solvent and a binder with relatively low polarity. Examples of low-polarity solvents include aromatic hydrocarbons. Examples of low-polarity binders include styrene-based elastomers. However, when low-polarity solvents and elastomers are used, the interaction between active material particles becomes stronger. Specifically, when low-polarity solvents and elastomers are used, the fluidity of the electrode composition may decrease. Therefore, in order to produce electrode sheets using low-polarity solvents and binders, a technology to improve the fluidity of the electrode composition is required.

[0011] The present inventors have investigated electrode compositions containing an active material and an elastomer-containing binder. As a result, they found that fluidity can be improved by coating the active material with a halide or sulfide solid electrolyte and including a styrene-based elastomer with a total nitrogen content of 30 ppm to 300 ppm, which exhibits moderate interaction with the solid electrolyte. More specifically, by introducing a modifying group, a nitrogen-containing functional group such as an amino group, into a styrene-based elastomer composed primarily of carbon (C) and hydrogen (H), polarity can be imparted to the styrene-based elastomer. As a result, adsorption occurs due to interaction between the N atoms contained in the styrene-based elastomer and the halide or sulfide solid electrolyte coating the active material, improving the affinity between the coated active material and the solvent and improving the fluidity of the electrode composition. From these perspectives, the present disclosure has been conceived.

[0012] In an electrode composition including a binder containing a styrene-based elastomer with a total nitrogen content of less than 30 ppm and an active material, the dispersibility of the active material in the electrode composition is reduced. This problem is thought to be caused by insufficient adsorption of the styrene-based elastomer to the active material. More specifically, it is thought that the above problem becomes apparent when the styrene-based elastomer has a total nitrogen content of less than 30 ppm, due to insufficient interaction with the active material.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0014] (Embodiment 1) FIG. 1 is a schematic diagram of an electrode composition 1000 according to embodiment 1. The electrode composition 1000 includes an ion conductor 112 and a solvent 104. The ion conductor 112 includes a coated active material 111 and a binder 103. The coated active material 111 includes an active material 101 and a coating layer 102 that coats at least a portion of the surface of the active material 101. The coating layer 102 includes a first solid electrolyte. The first solid electrolyte includes at least one selected from the group consisting of a halide solid electrolyte and a sulfide solid electrolyte. The ion conductor 112 is dispersed or dissolved in the solvent 104. Specifically, the coated active material 111 and the binder 103 are dispersed in the solvent 104. The binder 103 may be partially or completely dissolved in the solvent 104. The binder 103 includes a styrene-based elastomer. The total nitrogen content of the styrene-based elastomer is 30 ppm or more and 300 ppm or less.

[0015] The above-described configuration can improve the fluidity of the electrode composition 1000. By manufacturing an electrode sheet using the electrode composition 1000, an electrode sheet having a homogeneous and uniform thickness can be obtained. The electrode sheet having a homogeneous and uniform thickness can improve the energy density of the battery. The battery may be a liquid battery containing an electrolyte solution, or a solid battery not containing an electrolyte solution.

[0016] Controlling the total nitrogen content of the styrene-based elastomer, specifically, using a styrene-based elastomer with a total nitrogen content of 30 ppm or more and 300 ppm or less, can prevent the dispersibility of the coated active material 111 from being impaired. Because the first solid electrolyte contained in the coating layer 102 is a ceramic material that is sensitive to the polarity of the styrene-based elastomer that constitutes the binder 103, it is necessary to appropriately control the total nitrogen content of the styrene-based elastomer, specifically, on the order of ppm. As described above, in the electrode composition 1000, the total nitrogen content of the styrene-based elastomer that constitutes the binder 103 is 30 ppm or more and 300 ppm or less. This can improve the dispersibility of the coated active material 111 in the electrode composition 1000 and enhance the fluidity of the electrode composition.

[0017] The fluidity of the electrode composition 1000 can be evaluated by the shape of the flow curve obtained using a viscosity / viscoelasticity measuring device in rate control mode. FIG. 2 is a graph illustrating a method for evaluating the fluidity of the electrode composition 1000. In FIG. 2, the vertical axis represents the viscosity value of the electrode composition, and the horizontal axis represents the shear rate value. The fluidity of the electrode composition 1000 can be evaluated by the following method. First, using the viscosity / viscoelasticity measuring device, the viscosity of the electrode composition is measured at 25°C in rate control mode from a shear rate of 0.1 / sec to 1000 / sec, and the measurement results are plotted on the graph described above. If the graph shows a continuous decrease in viscosity of the electrode composition with increasing shear rate (plot A in FIG. 2), the electrode composition can be evaluated as having good fluidity. On the other hand, if the phenomenon of increasing viscosity with increasing shear rate, so-called dilatancy behavior, as shown in plot B in FIG. 2, is observed, the fluidity of the electrode composition can be evaluated as poor. The fluidity of the electrode composition can be evaluated as poor when the viscosity changes discontinuously with increasing shear rate, as shown by plot C in Fig. 2. The fluidity of the electrode composition can be evaluated as poor when the viscosity decreases rapidly with increasing shear rate, as shown by plot D in Fig. 2.

[0018] The electrode composition 1000 may be a fluid slurry. When the electrode composition 1000 has fluidity, it can be formed into an electrode sheet by a wet method such as a coating method. The "electrode sheet" may be a self-supporting sheet member, or may be a positive electrode layer or a negative electrode layer supported by a current collector, a substrate, or an electrode assembly.

[0019] The electrode composition 1000 will be described in detail below.

[0020] [Electrode composition] The electrode composition 1000 includes an ion conductor 112 and a solvent 104. The ion conductor 112 includes a coated active material 111 and a binder 103. The coated active material 111 includes an active material 101 and an active material 101 that at least partially coats the active material 101. The coating layer 102 includes a first solid electrolyte. The active material 101, the coating layer 102, the binder 103, the coated active material 111, the ion conductor 112, and the solvent 104 will be described in detail below.

[0021] <Active Material> The active material 101 in the first embodiment includes a material having the property of absorbing and releasing metal ions (e.g., lithium ions). The active material 101 includes, for example, a positive electrode active material or a negative electrode active material. When the electrode composition 1000 includes the active material 101, an electrode sheet obtained from the electrode composition 1000 can be used to manufacture a lithium secondary battery.

[0022] The active material 101 includes, for example, a material having the ability to absorb and release metal ions (e.g., lithium ions) as a positive electrode active material. Examples of positive electrode active materials include transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, transition metal oxynitrides, and lithium-containing compounds thereof. Examples of lithium-containing transition metal oxides include Li(NiCoAl)O2 (NCA), Li(NiCoMn)O2 (NCM), and LiCoO2. For example, using a lithium-containing transition metal oxide as the positive electrode active material can reduce the manufacturing cost of the electrode composition 1000 and improve the average discharge voltage of the battery. Li(NiCoAl)O2 refers to a composition containing Ni, Co, and Al in any ratio. Li(NiCoMn)O2 refers to a composition containing Ni, Co, and Mn in any ratio.

[0023] The median diameter of the positive electrode active material may be 0.1 μm or more and 100 μm or less, or 1 μm or more and 10 μm or less. When the median diameter of the positive electrode active material is 0.1 μm or more, the active material 101 can be easily dispersed in the solvent 104 in the electrode composition 1000. As a result, the charge / discharge characteristics of a battery using an electrode sheet manufactured from the electrode composition 1000 are improved. When the median diameter of the positive electrode active material is 100 μm or less, the lithium diffusion rate within the positive electrode active material is improved. Therefore, the battery can operate at high power.

[0024] The median diameter means the particle size at which the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is determined by a laser diffraction scattering method. The same applies to the other materials described below.

[0025] The active material 101 includes, for example, a negative electrode active material having the property of absorbing and releasing metal ions (e.g., lithium ions). Examples of the negative electrode active material include metal materials, carbon materials, oxides, nitrides, tin compounds, silicon compounds, and lithium-containing compounds thereof. The metal material may be a single metal or an alloy. Examples of the metal material include lithium metal and lithium alloys. Examples of the carbon material include natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. The use of silicon (Si), tin (Sn), silicon compounds, tin compounds, etc. can improve the capacity density of the battery. The use of a lithium-containing oxide containing titanium (Ti) or niobium (Nb) can improve the safety of the battery.

[0026] The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can be well dispersed in the negative electrode 303. This improves the charge / discharge characteristics of the battery. When the median diameter of the negative electrode active material is 100 μm or less, the lithium diffusion rate within the negative electrode active material improves. This allows the battery to operate at high power.

[0027] <Coating Layer> The coating layer 102 may uniformly coat the active material 101 .

[0028] The coating layer 102 may cover only a portion of the surface of the active material 101. Since the particles of the active material 101 are in direct contact with each other via the portion not covered by the coating layer 102, the electronic conductivity between the particles of the active material 101 is improved. As a result, the battery can operate at high power output.

[0029] A portion of the coating layer 102 may have a particle-like structure containing multiple particles. The particle diameter may be 3 μm or less, 1 μm or less, or 500 nm or less. Particles with a diameter of 3 μm or less are particles of the first solid electrolyte, which is the coating material. If the coating layer 102 has a fine particle-like structure, deformation of the coating layer 102 is promoted during battery manufacturing, thereby forming a good interface between the coated active material 111 and other materials. The lower limit of the particle diameter is not particularly limited and is, for example, 5 nm.

[0030] Here, "particle diameter" means the diameter of a spherical particle corresponding to the volume of the particle. Therefore, the expression "particle diameter" does not necessarily mean that the particle is spherical. The particle diameter is determined by a laser diffraction scattering method. The same applies to the other materials described below.

[0031] The particle-like structure refers to a structure in which a plurality of particles having a diameter of 3 μm or less are strung together and randomly arranged. The diameter of each of the plurality of particles constituting the particle-like structure may be 3 μm or less. The lower limit of the particle diameter is not particularly limited, and is, for example, 5 nm or more.

[0032] A particle-like structure comprising multiple particles with diameters of 3 μm or less can be formed by using particles with sufficiently small diameters as the coating material and appropriately adjusting the energy applied by the processing equipment when forming the coating layer 102.

[0033] The mass of the coating layer 102 can be 4.5% or less of the mass of the coated active material 111. If the mass of the coating layer 102 is 4.5% or less of the mass of the coated active material 111, the resistance of the battery can be further reduced. There is no particular lower limit to the mass of the coating layer 102, and it is, for example, 0.1% of the mass of the coated active material 111.

[0034] The coating layer 102 includes a first solid electrolyte. The first solid electrolyte has ion conductivity. The ion conductivity is typically lithium ion conductivity. The coating layer 102 may include the first solid electrolyte as a main component, or may include only the first solid electrolyte. "Main component" refers to the component that is most abundant by mass. "Includes only the first solid electrolyte" means that, with the exception of inevitable impurities, no materials other than the first solid electrolyte are intentionally added. For example, the inevitable impurities include raw materials for the first solid electrolyte and by-products generated during the production of the first solid electrolyte. The mass ratio of the inevitable impurities to the total mass of the coating layer 102 may be 5% or less, 3% or less, 1% or less, or 0.5% or less.

[0035] The median diameter of the particles of the coating material used to form the coating layer 102 may be 3 μm or less. When the median diameter of the particles of the coating material is 3 μm or less, the particles of the coating material can be spread uniformly on the surface of the active material 101. Furthermore, when mechanical energy is applied to the particles of the active material 101 and the coating material, the voids contained in the coating layer 102 are crushed, thereby forming a thin and uniform coating layer 102. The median diameter may be 1 μm or less, 500 nm or less, 100 nm or less, or 60 nm or less. The lower limit of the median diameter of the particles of the coating material is not particularly limited, and is, for example, 1 nm.

[0036] The particles of the coating material used to form the coating layer 102 may be particles of the first solid electrolyte.

[0037] In this specification, the term "particle" may refer to an aggregate of particles or a particle composed of a single particle, i.e., a particle may be a secondary particle or a primary particle.

[0038] The specific surface area of ​​the particles of the coating material used to form the coating layer 102 is 10 m 2 / g or more, 2 / g or more, 2 / g or more. When the specific surface area of ​​the particles of the coating material is large, they can be uniformly attached to the surface of the active material 101. As a result, a uniform coating layer 102 can be formed. The upper limit of the specific surface area of ​​the particles of the coating material is not particularly limited, and may be, for example, 100 m 2 / g.

[0039] The first solid electrolyte contained in the coating layer 102 includes a halide solid electrolyte or a sulfide solid electrolyte. The first solid electrolyte contained in the coating layer 102 may be a halide solid electrolyte. The first solid electrolyte contained in the coating layer 102 may be a sulfide solid electrolyte.

[0040] In the present disclosure, the term "halide solid electrolyte" refers to a solid electrolyte containing a halogen element but not containing sulfur. In the present disclosure, the term "sulfur-free solid electrolyte" refers to a solid electrolyte represented by a composition formula that does not contain sulfur. Therefore, a solid electrolyte containing only a trace amount of sulfur, for example, 0.1 mass% or less of sulfur, is included in the category of sulfur-free solid electrolyte. The halide solid electrolyte may further contain oxygen as an anion other than the halogen element.

[0041] The halide solid electrolyte contains, for example, Li, M, and X. M is at least one element selected from the group consisting of metal elements and semimetal elements other than Li. X is at least one element selected from the group consisting of F, Cl, Br, and I. The halide solid electrolyte has high thermal stability, which can improve the safety of the battery. Furthermore, the halide solid electrolyte does not contain sulfur, which can suppress the generation of hydrogen sulfide gas.

[0042] In the present disclosure, "metalloid elements" are B, Si, Ge, As, Sb and Te.

[0043] In the present disclosure, "metal element" refers to all elements included in Groups 1 to 12 of the periodic table excluding hydrogen, and all elements included in Groups 13 to 16 of the periodic table excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se.

[0044] Specifically, in the present disclosure, "metalloid elements" and "metal elements" are a group of elements that can become cations when forming an inorganic compound with a halogen element.

[0045] For example, the halide solid electrolyte as the first solid electrolyte may be a material represented by the following composition formula (1): Li α M β X γ ...Formula (1)

[0046] In the composition formula (1), α, β, and γ are independent of one another and are values ​​greater than 0. γ can be 4, 6, etc.

[0047] According to the above configuration, the ionic conductivity of the halide solid electrolyte is improved, which can improve the ionic conductivity of the electrode sheet formed from the electrode composition 1000. When used in a battery, this electrode sheet can further improve the output characteristics of the battery.

[0048] The halide solid electrolyte as the first solid electrolyte may be represented by the following composition formula (2): Li 6-nx M1 x X16...Formula (2)

[0049] In the composition formula (2), x satisfies 0<x≦1.2. n is the weighted average valence of the elements contained in M1. M1 is a metal or a metalloid. X1 is at least one element selected from the group consisting of F, Cl, Br, and I.

[0050] M1 may be at least one selected from the group consisting of Ca, Mg, Al, Y, Ti, and Zr. Specifically, M1 may be at least one selected from the group consisting of Al, Y, and Ti. By adding the above-mentioned elements, which are trivalent or tetravalent ions, to a crystal structure containing Li and X, the conduction path of lithium ions can be expanded. This configuration can improve the ionic conductivity of the coating layer 102 and effectively reduce the resistance of the battery.

[0051] In order to further increase the ionic conductivity of the first solid electrolyte, in the halide solid electrolyte, the ratio of the amount of substance of Li to the total amount of substance of M1 may be 1.7 or more and 4.2 or less. When the ratio of the amount of substance of Li to the total amount of substance of M1 is within the above range, the ionic conductivity of the first solid electrolyte can be further increased.

[0052] The halide solid electrolyte as the first solid electrolyte may consist essentially of Li, Ti, Al, and X1. Here, "the halide solid electrolyte consists essentially of Li, Ti, Al, and X" means that the molar ratio (i.e., molar fraction) of the total amount of substance of Li, Ti, Al, and X1 to the total amount of substance of all elements constituting the halide solid electrolyte is 90% or more. As an example, the molar ratio (i.e., molar fraction) may be 95% or more. The halide solid electrolyte may consist only of Li, Ti, Al, and X1.

[0053] X1 may contain fluorine (F). A fluorine-containing halide solid electrolyte exhibits high electrochemical stability, and can therefore improve the cycle characteristics of the battery.

[0054] The halide solid electrolyte as the first solid electrolyte may be a material represented by the following composition formula (3): Li 6-(4-x)b (Ti 1-x M1 x ) b F6...Formula (3)

[0055] In the composition formula (3), 0<x<1 and 0<b≦1.5 are satisfied. A halide solid electrolyte having such a composition has high ionic conductivity.

[0056] In order to further enhance the ionic conductivity of the halide solid electrolyte, M1 in the composition formula (3) may be Al.

[0057] In order to further enhance the ionic conductivity of the halide solid electrolyte, the relationship 0.1≦x≦0.9 may be satisfied in the composition formula (3).

[0058] In the composition formula (3), 0.1≦x≦0.7 may be satisfied.

[0059] The upper and lower limits of the range of x in composition formula (3) can be defined by any combination selected from the following numerical values: 0.1, 0.3, 0.4, 0.5, 0.6, 0.67, 0.7, 0.8, and 0.9.

[0060] In order to further enhance the ionic conductivity of the halide solid electrolyte, the relationship 0.8≦b≦1.2 may be satisfied in the composition formula (3).

[0061] The upper and lower limits of the range of b in composition formula (3) can be defined by any combination selected from the following numerical values: 0.8, 0.9, 0.94, 1.0, 1.06, 1.1, and 1.2.

[0062] The halide solid electrolyte may be a compound containing Li, M2, O (oxygen), and X2. The element M2 includes, for example, at least one element selected from the group consisting of Nb and Ta. Furthermore, X2 is at least one element selected from the group consisting of F, Cl, Br, and I.

[0063] The compound containing Li, M2, X2 and O (oxygen) has the composition formula: Li c M2O d X2 5+c-2d Here, c may satisfy 0.1<c<7.0, and d may satisfy 0.4<d<1.9.

[0064] More specifically, examples of halide solid electrolytes include LiY(Cl, Br, I), Li 2.7 Y 1.1 (Cl,Br,I)6, Li2Mg(F,Cl,Br,I)4, Li2Fe(F,Cl,Br,I)4, Li(Al,Ga,In)(F ,Cl,Br,I)4,Li3(Al,Ga,In)(F,Cl,Br,I)6,Li3(Ca,Y,Gd)(Cl,Br,I)6,Li 2.7 (Ti, Al)F6, Li 2.5Examples of usable elements include (Ti, Al)F6 and Li(Ta, Nb)O(F, Cl)4. In this disclosure, when an element in a formula is expressed as "(Al, Ga, In)," this notation indicates at least one element selected from the group of elements in parentheses. For example, "(Al, Ga, In)" is synonymous with "at least one element selected from the group consisting of Al, Ga, and In." The same applies to other elements.

[0065] Examples of sulfide solid electrolytes as the first solid electrolyte include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These sulfide solid electrolytes can be used with LiX, LiO, MO q , Li p MO q The element X in "LiX" is at least one element selected from the group consisting of F, Cl, Br, and I. q " and "Li p MO q " The element M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q " and "Li p MO q In the formula, p and q are natural numbers independent of each other. The sulfide solid electrolyte may be a glass ceramic type or an argyrodite type.

[0066] As the sulfide solid electrolyte, for example, Li2S-P2S5-based glass ceramics may be used. LiX, Li2O, MOq, LipMOq, etc. may be added to the Li2S-P2S5-based glass ceramics, or two or more selected from LiCl, LiBr, and LiI may be added. Because the Li2S-P2S5-based glass ceramics is a relatively soft material, an electrode sheet containing the Li2S-P2S5-based glass ceramics can be used to manufacture a battery with higher output.

[0067] In addition to the halide solid electrolyte or sulfide solid electrolyte that is the first solid electrolyte contained in the coating layer 102, the coating layer 102 may also contain an oxide material, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte. For example, the coating layer 102 containing the first solid electrolyte may contain a mixture of the first solid electrolyte and any of the above materials or electrolytes other than the first solid electrolyte within a single layer. In this case, the coating layer 102 may contain the first solid electrolyte as a main component, with the remaining components being materials other than the first solid electrolyte.

[0068] Examples of oxide materials used for the coating material include SiO2, Al2O3, TiO2, B2O3, Nb2O5, WO3, and ZrO2.

[0069] In the present disclosure, the term "oxide solid electrolyte" refers to a solid electrolyte containing oxygen. The oxide solid electrolyte may further contain anions other than sulfur and halogen elements as anions other than oxygen.

[0070] Examples of oxide solid electrolytes include NASICON-type solid electrolytes, such as LiTi2(PO4)3 and its elemental substitution products, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGeO 16 , Li4SiO4, LiGeO4 and their element substitution products, LiSICON type solid electrolytes, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those typified by element substitution products thereof, LiPO and its N-substituted products, glasses based on Li-B-O compounds such as LiBO and LiBO, and glass ceramics to which LiSO, LiCO, etc. are added, can be used.

[0071] Examples of oxide solid electrolytes used in the coating material include Li-Nb-O compounds such as LiNbO, Li-B-O compounds such as LiBO and LiBO, Li-Al-O compounds such as LiAlO, Li-Si-O compounds such as LiSiO, LiSO, and LiTiO. 12Examples of oxide solid electrolytes include Li-Ti-O compounds such as Li2ZrO3, Li-Zr-O compounds such as Li2MoO3, Li-V-O compounds such as LiVO5, Li-W-O compounds such as Li2WO4, and Li-P-O compounds such as LiPO4. Oxide solid electrolytes have high potential stability. Therefore, the use of oxide solid electrolytes as coating materials can improve the cycle performance of batteries.

[0072] The polymer solid electrolyte may be, for example, a compound of a polymer compound and a lithium salt. The polymer compound may have an ethylene oxide structure. A polymer compound having an ethylene oxide structure may contain a large amount of lithium salt. This can further improve ionic conductivity. Examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. When a lithium salt is used, only one type of lithium salt may be used alone, or two or more types of lithium salts may be used in combination.

[0073] Examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI and LiBH4-P2S5.

[0074] The shape of the particles of the first solid electrolyte and the above-mentioned material or electrolyte other than the first solid electrolyte is not particularly limited, and may be acicular, spherical, ellipsoidal, etc. The shape of the solid electrolyte may be particulate.

[0075] When the first solid electrolyte has a particulate (eg, spherical) shape, the first solid electrolyte may have a median diameter of 0.01 μm or more and 100 μm or less.

[0076] The thickness of the coating layer 102 may be, for example, 1 nm or more and 500 nm or less. When the thickness of the coating layer 102 is adjusted to the above thickness, contact between the active material 101 and other materials can be sufficiently suppressed. The thickness of the coating layer 102 can be determined by slicing the coated active material 111 by a method such as ion milling and observing the cross section of the coated active material 111 with a transmission electron microscope. The average value of thicknesses observed at any multiple positions (e.g., five points) can be considered to be the thickness of the coating layer 102.

[0077] The coating layer 102 may be composed of a single layer. For example, the coating layer 102 may be a single coating layer composed only of one type of first solid electrolyte. Alternatively, the coating layer 102 may be a single coating layer composed of materials selected from multiple types of the first solid electrolyte. The coating layer 102 may be composed of multiple layers. For example, the coating layer 102 may be a multiple-layer coating layer, each layer being composed of a material selected from multiple types of the first solid electrolyte. Alternatively, the coating layer 102 may be two layers, one layer composed of a halide solid electrolyte and one layer composed of a sulfide solid electrolyte. This configuration can achieve both improved cycle characteristics and output characteristics of the battery.

[0078] When multiple coating layers 102 are provided, the outermost layer of the coating layer 102 may be composed of a layer containing the first solid electrolyte. When the outermost layer contains the first solid electrolyte, the outermost layer does not have to contain an oxide solid electrolyte. When the outermost layer does not contain an oxide solid electrolyte, the coating layer 102 contains a larger amount of the first solid electrolyte that has a high affinity with the styrene-based elastomer contained in the binder 103 described below. Therefore, by providing the coating layer 102 in the outermost layer that is likely to come into contact with the styrene-based elastomer contained in the binder 103, the effect of improving fluidity is enhanced. The coating layer 102 contains the first solid electrolyte that has a high affinity with the styrene-based elastomer contained in the binder 103 described below. Therefore, by providing the coating layer 102 in the outermost layer that is likely to come into contact with the styrene-based elastomer contained in the binder 103, the effect of improving fluidity is enhanced. The inner layer of the coating layer 102 between the active material 101 and the outermost layer of the coating layer 102 is not particularly limited and may be composed of a layer containing a material other than the first solid electrolyte. The layer containing a material other than the first solid electrolyte may contain an oxide material, an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte. The material constituting the inner layer may be an oxide solid electrolyte, a polymer solid electrolyte, or a complex hydride solid electrolyte. The layer containing the first solid electrolyte may be a layer containing the first solid electrolyte as a main component, or may be a layer containing only the first solid electrolyte. The layer containing the above material or the above electrolyte other than the first solid electrolyte may be a layer containing the material or electrolyte as a main component, or may be a layer containing only the material or electrolyte.

[0079] The layer containing the first solid electrolyte does not necessarily have to be the outermost layer, and may be composed of, for example, the above-mentioned material or electrolyte other than the first solid electrolyte. When the outermost layer is a layer other than the first solid electrolyte and the inner layer in contact with the outermost layer is a layer containing the first solid electrolyte, for example, the outermost layer covers 80% or less of the surface area of ​​the layer containing the first solid electrolyte.

[0080] The coating layer 102 is produced, for example, by the following method.

[0081] A powder of the active material 101 and a powder of the first solid electrolyte are mixed in an appropriate ratio to obtain a mixture. The mixture is then milled to impart mechanical energy to the mixture. A mixing device such as a ball mill can be used for the milling process. The milling process may be performed in a dry and inert atmosphere to prevent oxidation of the materials.

[0082] The coated active material 111 may be manufactured by a dry particle compositing method. The treatment by the dry particle compositing method includes applying at least one mechanical energy selected from the group consisting of impact, compression, and shear to the active material 101 and the first solid electrolyte. The active material 101 and the first solid electrolyte are mixed in an appropriate ratio.

[0083] The apparatus used in producing the coated active material 111 is not particularly limited and may be an apparatus capable of applying impact, compression, or shear mechanical energy to the mixture of the active material 101 and the first solid electrolyte. Examples of apparatus capable of applying mechanical energy include processing apparatuses (particle composite apparatuses) such as a ball mill, Mechanofusion (manufactured by Hosokawa Micron Corporation), Nobilta (manufactured by Hosokawa Micron Corporation), and Balance Gran (manufactured by Freund Turbo Corporation).

[0084] "Mechanofusion" is a particle compounding device that uses a dry mechanical compounding technology by applying strong mechanical energy to multiple different raw material powders. In mechanofusion, raw material powders are placed between a rotating container and a press head, and mechanical energy of compression, shear, and friction is applied to them. This causes the particles to compound.

[0085] "Nobilta" is a particle compounding device that uses dry mechanical compounding technology, an advanced form of particle compounding technology, to compound nanoparticles as raw materials. Nobilta produces composite particles by applying mechanical energy of impact, compression, and shear to multiple types of raw material powders.

[0086] In the Nobilta, a rotor positioned at a predetermined gap between itself and the inner wall of a horizontal cylindrical mixing vessel rotates at high speed, forcing the raw material powder through the gap, a process that is repeated multiple times. This applies impact, compression, and shear forces to the mixture, producing composite particles of active material 101 and the first solid electrolyte. By adjusting conditions such as the rotor rotation speed, processing time, and feed amount, the thickness of coating layer 102 and the specific surface area of ​​coated active material 111 can be controlled.

[0087] However, processing using the above-mentioned apparatus is not essential. The coated active material 111 may be produced by mixing the active material 101 and the first solid electrolyte using a mortar, a planetary mixer, a kneader, or the like. The mixing method may be either a dry method or a wet method using a solvent. The first solid electrolyte may be deposited on the surface of the active material 101 by various methods such as a spray method, a spray-dry coating method, an electrodeposition method, an immersion method, or a mechanical mixing method using a disperser.

[0088] <Binder> The binder 103 can improve the dispersibility of the particles of the active material 101, solid electrolyte, and / or coated active material 111 in the electrode composition 1000 by improving the wettability of these particles with the solvent 104. In addition, the binder 103 can improve the dispersion stability by suppressing aggregation between particles of the active material 101, solid electrolyte, and / or coated active material 111 in the electrode composition 1000. The binder 103 can improve the adhesion between particles of the active material 101, solid electrolyte, and coated active material 111 in the electrode sheet.

[0089] The binder 103 includes a styrene-based elastomer. The styrene-based elastomer refers to an elastomer containing a repeating unit derived from styrene. The repeating unit refers to a molecular structure derived from a monomer and is sometimes called a constituent unit. The styrene-based elastomer has excellent flexibility and elasticity, making it suitable for the binder 103 of the electrode sheet. The content of the repeating unit derived from styrene in the styrene-based elastomer is not particularly limited, and is, for example, 10% by mass or more and 70% by mass or less.

[0090] The styrene-based elastomer may be a copolymer containing butadiene or isoprene as a conjugated diene monomer. Furthermore, the repeating units derived from the conjugated diene may be partially or entirely hydrogenated. That is, the repeating units derived from the conjugated diene may or may not have an unsaturated bond such as a carbon-carbon double bond.

[0091] The styrene-based elastomer may be a block copolymer containing a first block composed of repeating units derived from styrene and a second block composed of repeating units derived from a conjugated diene. Examples of conjugated dienes include butadiene and isoprene. The repeating units derived from the conjugated diene may be hydrogenated. That is, the repeating units derived from the conjugated diene may or may not have an unsaturated bond such as a carbon-carbon double bond. The block copolymer may have a triblock arrangement composed of two first blocks and one second block. The block copolymer may be an ABA triblock copolymer. In this triblock copolymer, the A block corresponds to the first block and the B block corresponds to the second block. The first block functions, for example, as a hard segment. The second block functions, for example, as a soft segment.

[0092] Examples of styrene-based elastomers include styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), and hydrogenated styrene-butadiene rubber (HSBR). The binder 103 may contain SBR or SEBS as a styrene-based elastomer. A mixture containing two or more selected from these may also be used as the binder 103. Because styrene-based elastomers have excellent flexibility and elasticity, the binder 103 containing a styrene-based elastomer can improve the surface smoothness of an electrode sheet manufactured from the electrode composition 1000. Furthermore, the binder 103 containing a styrene-based elastomer can impart flexibility to the electrode sheet. As a result, the durability of the battery can be improved.

[0093] The styrene-based elastomer may be a styrene-based triblock copolymer. Examples of styrene-based triblock copolymers include styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), styrene-butadiene-styrene block copolymer (SBS), and styrene-isoprene-styrene block copolymer (SIS). These styrene-based triblock copolymers are sometimes called styrene-based thermoplastic elastomers. These styrene-based triblock copolymers tend to be flexible and have high strength.

[0094] The total nitrogen content of the styrene-based elastomer is 30 ppm or more and 300 ppm or less. The total nitrogen content of the styrene-based elastomer may be 50 ppm or more and 250 ppm or less, or 80 ppm or more and 200 ppm or less. The total nitrogen content is determined using a trace total nitrogen analyzer. Specifically, the mass (μg) of nitrogen (N) contained in 1 g of polymer is measured using a Nitto Seiko Analytech trace total nitrogen analyzer (TN-2100H) using a pyridine / toluene solution as a standard sample. The total nitrogen content is the ratio of the mass (μg) of nitrogen (N) contained in 1 g of polymer (μg / g = ppm).

[0095] The method for determining the total nitrogen content of the styrene-based elastomer contained in a battery product is as follows. First, organic matter contained in the electrodes of the battery product is extracted using an aromatic solvent such as toluene, which dissolves the styrene-based elastomer. Chromatography is then performed to isolate the styrene-based elastomer from the extracted organic matter. At this time, gel permeation chromatography (GPC) may be used to remove low-molecular-weight organic matter other than the styrene-based elastomer, or a more precise GPC column may be used. At this time, nuclear magnetic resonance analysis (NMR) and / or infrared absorption spectroscopy (IR analysis) may be used to confirm the isolation. Next, trace total nitrogen analysis is performed on the isolated styrene-based elastomer solution to determine the total nitrogen content of the styrene-based elastomer.

[0096] The styrene-based elastomer may contain a modifying group having a nitrogen atom. The modifying group refers to a functional group that chemically modifies all repeating units in the polymer chain, some repeating units in the polymer chain, or the terminal portion of the polymer chain. The modifying group can be introduced into the polymer chain by substitution reaction, addition reaction, or the like. The modifying group having a nitrogen atom is a nitrogen-containing functional group, such as an amino group, a nitrile group, or a nitro group. The modifying group having a nitrogen atom can be introduced into the polymer chain by, for example, reacting it with a modifying agent. Examples of modifying compounds include amine compounds, isocyanate compounds, isothiocyanate compounds, isocyanuric acid derivatives, nitrogen-containing carbonyl compounds, nitrogen-containing vinyl compounds, nitrogen-containing epoxy compounds, and nitrogen-containing alkoxysilane compounds. The modifying group may be located at the terminal of the polymer chain. A styrene-based elastomer having a modifying group at the terminal of the polymer chain may have an effect similar to that of a surfactant. That is, by using a styrene-based elastomer having a modifying group at the end of the polymer chain, the modifying group adsorbs to the active material and / or solid electrolyte, and the polymer chain can suppress aggregation of particles of the active material 101 and / or solid electrolyte. As a result, the dispersibility of the active material 101 and / or solid electrolyte can be further improved. The styrene-based elastomer may be, for example, an amine-terminated styrene-based elastomer. The styrene-based elastomer may be, for example, a styrene-based elastomer having a nitrogen atom at at least one end of the polymer chain and having a star polymer structure centered on a nitrogen-containing alkoxysilane substituent.

[0097] In addition to the nitrogen-containing modifying group, the styrene-based elastomer may further contain a modifying group containing an atom other than nitrogen. The modifying group containing an atom other than nitrogen may contain, for example, elements with relatively high electronegativity such as O, S, F, Cl, Br, and F, or elements with relatively low electronegativity such as Si, Sn, and P. Modifying groups containing such elements can impart polarity to the styrene-based elastomer. Examples of modifying groups include carboxylic acid groups, acid anhydride groups, acyl groups, hydroxy groups, sulfo groups, sulfanyl groups, phosphate groups, phosphonate groups, isocyanate groups, epoxy groups, and silyl groups. A specific example of an acid anhydride group is a maleic anhydride group. The modifying group may also be a functional group that can be introduced by reacting a modifying agent containing the following compounds: Examples of the modifying agent include epoxy compounds, ether compounds, ester compounds, mercapto group derivatives, thiocarbonyl compounds, halogenated silicon compounds, epoxidized silicon compounds, vinylated silicon compounds, alkoxy silicon compounds, halogenated tin compounds, organotin carboxylate compounds, phosphite ester compounds, and phosphino compounds. When the styrene-based elastomer contains the above-mentioned modifying group, the dispersibility of the active material 101 and / or solid electrolyte contained in the electrode composition 1000 can be further improved. Furthermore, the peel strength of the electrode sheet can be improved by interaction with the current collector.

[0098] The weight-average molecular weight (Mw) of the styrene-based elastomer may be 200,000 or more. The weight-average molecular weight (Mw) of the styrene-based elastomer may be 300,000 or more, 500,000 or more, 800,000 or more, or 1,000,000 or more. The upper limit of the weight-average molecular weight (Mw) is, for example, 1,500,000. When the weight-average molecular weight (Mw) of the styrene-based elastomer is 200,000 or more, excessive increase in the total nitrogen content of the styrene-based elastomer can be suppressed. Furthermore, particles of the active material 101 and / or solid electrolyte can be bonded to each other with sufficient adhesive strength. When the weight-average molecular weight (Mw) of the styrene-based elastomer is 1,500,000 or less, electronic conduction between particles of the active material 101 and / or ionic conduction between particles of the solid electrolyte are less likely to be inhibited by the binder 103, thereby improving the output characteristics of the battery. The weight-average molecular weight (Mw) of the styrene-based elastomer contained in the binder 103 can be determined, for example, by gel permeation chromatography (GPC) measurement using polystyrene as a standard sample. In other words, the weight-average molecular weight (Mw) is a value converted into polystyrene. In the GPC measurement, chloroform may be used as an eluent. When two or more peak tops are observed in the chart obtained by the GPC measurement, the weight-average molecular weight (Mw) calculated from the entire peak range including each peak top can be considered as the weight-average molecular weight (Mw) of the styrene-based elastomer.

[0099] In a styrene-based elastomer, the ratio of the degree of polymerization of repeating units derived from styrene to the degree of polymerization of repeating units derived from other than styrene is defined as m:n. In this case, the molar fraction of repeating units derived from styrene (hereinafter also simply referred to as "φ") in a styrene-based elastomer can be calculated by φ = m / (m + n). In a styrene-based elastomer, the molar fraction (φ) of repeating units derived from styrene can be calculated by, for example, proton nuclear magnetic resonance ( 1 It can be determined by H NMR measurement.

[0100] In the styrene-based elastomer, the molar fraction (φ) of repeating units derived from styrene may be 0.02 or more and 0.55 or less, or 0.1 or more and 0.3 or less. When the φ of the styrene-based elastomer is 0.02 or more, the strength of the electrode sheet can be improved. When the φ of the styrene-based elastomer is 0.55 or less, the flexibility of the electrode sheet can be improved.

[0101] The styrene-based elastomer may include at least one selected from the group consisting of modified SEBS and modified SBR. Modified SEBS refers to SEBS into which a modifying group has been introduced. Modified SBR refers to SBR into which a modifying group has been introduced. The modifying group includes a modifying group having a nitrogen atom. The modifying group may further include a modifying group having an atom other than a nitrogen atom. The modified SEBS or modified SBR may be produced by solution polymerization or by solution anionic polymerization using an organolithium catalyst. Solution anionic polymerization is a production method that excels in controlling the molecular weight of the polymer and / or the amount of modifying group introduced. Therefore, a more optimal electrode composition 1000 can be produced by using modified SEBS produced by solution polymerization or modified SBR produced by solution polymerization.

[0102] The styrene-based elastomer may include modified SBR. The styrene-based elastomer may be modified SBR. Modified SBR tends to be more easily compressed during hot and pressure molding than modified SEBS. This can further improve the filling of the ionic conductor 112 contained in the electrode sheet produced from the electrode composition 1000.

[0103] The styrene-based elastomer may be an oil-extended polymer blended with process oil or the like to improve processability. Examples of process oils include aromatic oils, paraffinic oils, naphthenic oils, vegetable oils, and oils with a low content of polycyclic aromatic compounds (low PCA oils). Low PCA oils may also be used. Examples of low PCA oils include mild extract solvates (MES), oils obtained by treating aromatic extracts from distillate oils (TDAE), special aromatic extracts from residual oils (SRAE), and heavy naphthenic oils. The mass ratio of the process oil to the mass of the styrene-based elastomer is not particularly limited and may be, for example, 10% by mass or more and 100% by mass or less. By including process oil in the binder 103, the process oil acts as a lubricant, improving the packing of the ionic conductor 112.

[0104] The mass ratio of the process oil to the mass of the styrene-based elastomer may be 1 mass% or less. By setting the mass ratio of the process oil to the mass of the styrene-based elastomer to 1 mass% or less, it is possible to suppress the reaction between the process oil and the solid electrolyte and improve the cycle characteristics of the battery. When the styrene-based elastomer is an oil-extended polymer, the oil contained in the styrene-based elastomer can be removed by dissolving the styrene-based elastomer in tetrahydrofuran (THF), followed by reprecipitation in ethanol and washing with acetone.

[0105] The binder 103 may contain a resin binder other than a styrene-based elastomer, such as a binding agent that can generally be used as a binder for batteries. Alternatively, the binder 103 may be a styrene-based elastomer. In other words, the binder 103 may contain only a styrene-based elastomer.

[0106] Examples of binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate (PMMA), polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polycarbonate, polyethersulfone, polyetherketone, polyetheretherketone, polyphenylene sulfide, hexafluoropolypropylene, styrene-butadiene rubber, carboxymethyl cellulose, and ethyl cellulose. The binder may also be a copolymer synthesized using two or more monomers selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, butadiene, isoprene, styrene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid ester, acrylic acid, and hexadiene. These may be used alone or in combination of two or more.

[0107] The binder may contain an elastomer from the viewpoint of excellent binding properties. Elastomer refers to a polymer having rubber elasticity. The elastomer used as the binder may be a thermoplastic elastomer or a thermosetting elastomer. In addition to the styrene-based elastomers described above, examples of the elastomer include butadiene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), and acrylate butadiene rubber (ABR). A mixture containing two or more selected from these may also be used.

[0108] <Ionic Conductor> As described above, the ionic conductor 112 includes the coated active material 111 and the binder 103. In the ionic conductor 112, a plurality of particles of the coated active material 111 are bound together via the styrene-based elastomer contained in the binder 103. In the ionic conductor 112, for example, the particles of the coated active material 111 are uniformly dispersed due to the styrene-based elastomer contained in the binder 103 that is adsorbed to the coated active material 111.

[0109] In the ion conductor 112, the ratio of the mass of the binder 103 to the mass of the coated active material 111 is not particularly limited, and may be 0.1 mass% or more and 10 mass% or less, 0.2 mass% or more and 5 mass% or less, or 0.3 mass% or more and 1 mass% or less. When the ratio of the mass of the binder 103 to the mass of the coated active material 111 is 0.1 mass% or more, the strength of the electrode sheet manufactured from the electrode composition 1000 can be improved. When the ratio of the mass of the binder 103 to the mass of the coated active material 111 is 10 mass% or less, a decrease in the ionic conductivity of the ion conductor 112 can be suppressed.

[0110] The ionic conductor 112 can be prepared, for example, by mixing the coated active material 111 and the binder 103. The mixing method is not particularly limited, and examples include a method in which the coated active material 111 and the binder 103 are mechanically pulverized and mixed in a dry manner. A wet method may also be used in which a solution or dispersion containing the binder 103 is prepared, the coated active material 111 is dispersed in the solution or dispersion, and the resulting mixture is mixed. The wet method allows the binder 103 and the coated active material 111 to be mixed simply and uniformly. The electrode composition 1000 may also be prepared by preparing the ionic conductor 112 in the solvent 104 by the wet method.

[0111] <Solvent> The solvent 104 may be an organic solvent. The organic solvent is a compound containing carbon, such as a compound containing elements such as carbon, hydrogen, nitrogen, oxygen, sulfur, and halogen.

[0112] The solvent 104 may include at least one selected from the group consisting of hydrocarbons, compounds having a halogen group, and compounds having an ether bond.

[0113] The solvent 104 may include at least one selected from the group consisting of hydrocarbons, compounds having a halogen group, and compounds having an ether bond.

[0114] A hydrocarbon is a compound consisting only of carbon and hydrogen. The hydrocarbon may be an aliphatic hydrocarbon. The hydrocarbon may be a saturated hydrocarbon or an unsaturated hydrocarbon. The hydrocarbon may be linear or branched. The number of carbon atoms contained in the hydrocarbon is not particularly limited and may be 7 or more. By using a hydrocarbon, an electrode composition 1000 with excellent dispersibility of the ionic conductor 112 can be obtained. Furthermore, a decrease in the ionic conductivity of the ionic conductor 112 due to mixing with the solvent 104 can be suppressed.

[0115] The hydrocarbon may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be monocyclic or polycyclic. When the hydrocarbon has a ring structure, the ionic conductor 112 can be easily dispersed in the solvent 104. From the viewpoint of improving the dispersibility of the ionic conductor 112 in the electrode composition 1000, the hydrocarbon may contain an aromatic hydrocarbon. That is, the solvent 104 may contain an aromatic hydrocarbon. The hydrocarbon may be an aromatic hydrocarbon. A styrene-based elastomer is easily soluble in an aromatic hydrocarbon. Therefore, when the binder 103 contains a styrene-based elastomer and the solvent 104 further contains an aromatic hydrocarbon, the binder 103 can be more efficiently adsorbed to the coated active material 111 in the electrode composition 1000. This can further improve the solvent retention performance of the electrode composition 1000. Furthermore, aromatic hydrocarbons have relatively low polarity. Therefore, when the solvent 104 contains an aromatic hydrocarbon, excessive adsorption of the solvent 104 to the coated active material 111 can be suppressed. In addition, when the solvent 104 contains an aromatic hydrocarbon, a decrease in ionic conductivity due to a reaction between the solid electrolyte and the solvent 104 can be suppressed.

[0116] The compound having a halogen group may be composed only of carbon and hydrogen in the portion other than the halogen group. In other words, a compound having a halogen group refers to a compound in which at least one hydrogen atom contained in a hydrocarbon is substituted with a halogen group. Examples of the halogen group include F, Cl, Br, and I. The halogen group may be at least one selected from the group consisting of F, Cl, Br, and I. Substituting at least one hydrogen atom contained in a hydrocarbon with a halogen group can impart relatively low polarity to the hydrocarbon. By using a compound having a halogen group as the solvent 104, the ionic conductor 112 can be easily dispersed in the solvent 104, thereby obtaining an electrode composition 1000 with excellent dispersibility. As a result, an electrode sheet manufactured from the electrode composition 1000 can have excellent ionic conductivity and a denser structure.

[0117] The number of carbon atoms contained in the compound having a halogen group is not particularly limited and may be 7 or more. This makes the compound having a halogen group less likely to volatilize, allowing the electrode composition 1000 to be produced stably. The compound having a halogen group may have a large molecular weight. In other words, the compound having a halogen group may have a high boiling point.

[0118] The compound having a halogen group may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be a monocyclic or a polycyclic. When the compound having a halogen group has a ring structure, the ionic conductor 112 can be easily dispersed in the solvent 104. From the viewpoint of improving the dispersibility of the ionic conductor 112 in the electrode composition 1000, the compound having a halogen group may contain an aromatic hydrocarbon. The compound having a halogen group may be an aromatic hydrocarbon substituted with a halogen group.

[0119] The compound having a halogen group may have only a halogen group as a functional group. In this case, the number of halogens contained in the compound having a halogen group is not particularly limited. At least one selected from the group consisting of F, Cl, Br, and I may be used as the halogen group. By using such a compound in the solvent 104, the ionic conductor 112 can be easily dispersed in the solvent 104, thereby obtaining an electrode composition 1000 with excellent dispersibility. As a result, the electrode sheet manufactured from the electrode composition 1000 can have excellent ionic conductivity and a denser structure. By using such a compound in the solvent 104, the electrode sheet manufactured from the electrode composition 1000 can easily have a dense structure with fewer pinholes, unevenness, etc.

[0120] The compound having a halogen group may be a halogenated hydrocarbon. A halogenated hydrocarbon refers to a compound in which all hydrogen atoms contained in a hydrocarbon are substituted with halogen groups. By using a halogenated hydrocarbon as the solvent 104, the ionic conductor 112 can be easily dispersed in the solvent 104, thereby obtaining an electrode composition 1000 with excellent dispersibility. As a result, an electrode sheet manufactured from the electrode composition 1000 can have excellent ionic conductivity and a denser structure. By using such a compound as the solvent 104, an electrode sheet manufactured from the electrode composition 1000 can easily have a denser structure with fewer pinholes, irregularities, and the like.

[0121] The compound having an ether bond may be composed solely of carbon and hydrogen in the portion other than the ether bond. In other words, a compound having an ether bond refers to a compound in which at least one C-C bond in a hydrocarbon is substituted with a C-O-C bond. Substituting at least one C-C bond in a hydrocarbon with a C-O-C bond can impart relatively low polarity to the hydrocarbon. By using a compound having an ether bond in the solvent 104, the ionic conductor 112 can be easily dispersed in the solvent 104. Therefore, an electrode composition 1000 with excellent dispersibility can be obtained. As a result, an electrode sheet manufactured from the electrode composition 1000 can have excellent ionic conductivity and a denser structure.

[0122] The compound having an ether bond may have a ring structure. The ring structure may be an alicyclic hydrocarbon or an aromatic hydrocarbon. The ring structure may be monocyclic or polycyclic. When the compound having an ether bond has a ring structure, the ionic conductor 112 can be easily dispersed in the solvent 104. From the viewpoint of improving the dispersibility of the ionic conductor 112 in the electrode composition 1000, the compound having an ether bond may contain an aromatic hydrocarbon. The compound having an ether bond may be an aromatic hydrocarbon substituted with an ether group.

[0123] Examples of the solvent 104 include ethylbenzene, mesitylene, pseudocumene, p-xylene, cumene, tetralin, m-xylene, dibutyl ether, 1,2,4-trichlorobenzene, chlorobenzene, 2,4-dichlorotoluene, anisole, o-chlorotoluene, m-dichlorobenzene, p-chlorotoluene, o-dichlorobenzene, 1,4-dichlorobutane, and 3,4-dichlorotoluene. These may be used alone or in combination of two or more.

[0124] From the viewpoint of cost, commercially available xylene, that is, mixed xylene, may be used as the solvent 104. For example, mixed xylene in which o-xylene, m-xylene, p-xylene, and ethylbenzene are mixed in a mass ratio of 24:42:18:16 may be used as the solvent 104.

[0125] The solvent 104 may contain tetralin, which has a relatively high boiling point. Tetralin not only improves the solvent retention performance of the electrode composition 1000, but also enables the electrode composition 1000 to be stably produced by the kneading process.

[0126] The boiling point of the solvent 104 may be 100°C or higher and 250°C or lower, 130°C or higher and 230°C or lower, 150°C or higher and 220°C or lower, or 180°C or higher and 210°C or lower. The solvent 104 may be liquid at room temperature (25°C). Such a solvent is less likely to volatilize at room temperature, allowing the electrode composition 1000 to be stably produced. Therefore, an electrode composition 1000 that can be easily applied to the surface of a substrate can be obtained. The solvent 104 contained in the electrode composition 1000 can be easily removed by drying, which will be described later.

[0127] The water content of the solvent 104 may be 10 ppm by mass or less. By reducing the water content, it is possible to suppress a decrease in ionic conductivity due to a reaction of the solid electrolyte. Methods for reducing the water content include a dehydration method using a molecular sieve and a dehydration method using bubbling with an inert gas such as nitrogen gas or argon gas. From the viewpoint of being able to remove oxygen simultaneously with water, a dehydration method using bubbling with an inert gas is recommended. The water content can be measured using a Karl Fischer water content analyzer.

[0128] The solvent 104 disperses the ion conductor 112. The solvent 104 can be a liquid capable of dispersing the coated active material 111. The coated active material 111 does not have to be dissolved in the solvent 104. Since the coated active material 111 does not dissolve in the solvent 104, it is possible to produce an electrode composition 1000 in which the ion-conducting phase formed during the production of the first solid electrolyte contained in the coating layer 102 of the coated active material 111 is maintained. Therefore, an electrode sheet produced using this electrode composition 1000 can suppress a decrease in ionic conductivity.

[0129] The solvent 104 may partially dissolve the coated active material 111. By dissolving the coated active material 111, the density of the electrode sheet produced using this electrode composition 1000 can be improved.

[0130] <Electrode Composition> The electrode composition 1000 may be in a paste form or a dispersion state. The coated active material 111 is, for example, particles. In producing the electrode composition 1000, particles of the ion conductor 112 are mixed with the solvent 104. In producing the electrode composition 1000, the method of mixing the ion conductor 112 with the solvent 104, i.e., the method of mixing the coated active material 111, the binder 103, and the solvent 104, is not particularly limited. For example, mixing methods using a mixing device such as a stirring type, a shaking type, an ultrasonic type, or a rotary type are exemplified. For example, mixing methods using a dispersion kneading device such as a high-speed homogenizer, a thin film rotary high-speed mixer, an ultrasonic homogenizer, a ball mill, a bead mill, a planetary mixer, a sand mill, a roll mill, or a kneader are exemplified. These mixing methods may be used alone or in combination of two or more types.

[0131] The electrode composition 1000 is produced, for example, by the following method. First, the coated active material 111 and the solvent 104 are mixed, and then a binder solution is added. The resulting mixture is subjected to high-speed shear treatment using an in-line disperser / pulverizer. The binder solution is added to the resulting dispersion. The resulting mixture is subjected to high-speed shear treatment using an in-line disperser / pulverizer. Through these steps, the ionic conductor 112 is formed, and the ionic conductor 112 is dispersed and stabilized in the solvent 104, thereby producing an electrode composition 1000 with excellent fluidity. The electrode composition 1000 may also be produced by mixing the solvent 104 with the ionic conductor 112 that has been prepared in advance, and then subjecting the resulting mixture to high-speed shear treatment.

[0132] The electrode composition 1000 may be produced by, for example, the following method. First, the coated active material 111 and the solvent 104 are mixed, and then a binder solution is added. The resulting mixture is subjected to high shear treatment using an ultrasonic homogenizer. The binder solution is added to the resulting dispersion. The resulting mixture is subjected to high shear treatment using an ultrasonic homogenizer. Through these steps, the ionic conductor 112 is formed, and the ionic conductor 112 is dispersed and stabilized in the solvent 104, thereby producing an electrode composition 1000 with excellent fluidity. The electrode composition 1000 may be produced by mixing the solvent 104 with the ionic conductor 112 that has been prepared in advance, and then subjecting the resulting mixture to high shear treatment using ultrasound.

[0133] From the viewpoint of producing an electrode composition 1000 having excellent fluidity, high-speed shear treatment or high-shear treatment using ultrasound may be performed under conditions that do not cause pulverization of the particles of the coated active material 111, but do cause the particles of the coated active material 111 to break apart from each other.

[0134] The binder solution is, for example, a solution containing a binder 103 and a solvent 104. The composition of the solvent contained in the binder solution may be the same as or different from the composition of the solvent contained in the dispersion of the coated active material 111.

[0135] FIG. 3 is a schematic diagram of an electrode composition 1001 according to a modified example. The electrode composition 1001 includes an ion conductor 122 and a solvent 104. The ion conductor 122 includes a coated active material 111, a second solid electrolyte 105, and a binder 103. That is, the electrode composition 1001 is obtained by further adding a second solid electrolyte 105 to the electrode composition 1000 for the purpose of improving ion conductivity. The second solid electrolyte may be the same material as the first solid electrolyte, or may include a solid electrolyte different from the first solid electrolyte, as described above. For example, a halide solid electrolyte may be used as the first solid electrolyte contained in the coating layer 102 of the coated active material 111, and a sulfide solid electrolyte may be used as the second solid electrolyte.

[0136] When the second solid electrolyte 105 is particulate (e.g., spherical), the median diameter of the second solid electrolyte 105 may be 1 μm or more and 100 μm or less, or 1 μm or more and 10 μm or less. When the median diameter of the second solid electrolyte 105 is 1 μm or more and 100 μm or less, the second solid electrolyte 105 can be easily dispersed in the solvent 104.

[0137] When the second solid electrolyte 105 is particulate (for example, spherical), the median diameter of the second solid electrolyte 105 may be 0.1 μm or more and 5 μm or less, or 0.5 μm or more and 3 μm or less. When the median diameter of the second solid electrolyte 105 is 0.1 μm or more and 5 μm or less, an electrode sheet manufactured from the electrode composition 1001 may have higher surface smoothness and a denser structure.

[0138] The specific surface area of ​​the second solid electrolyte 105 is 0.1 m 2 / g or more 100m 2 / g or less, 2 / g or more 10m 2 The specific surface area of ​​the second solid electrolyte 105 may be 0.1 m / g or less. 2 / g or more 100m 2 When the specific surface area is 1 / g or less, the second solid electrolyte 105 can be easily dispersed in the solvent 104. The specific surface area can be measured by a BET multipoint method using a gas adsorption measurement device.

[0139] The ionic conductivity of the second solid electrolyte 105 is 0.01 mS / cm 2 or more, and may be 0.1 mS / cm 2 or more, and 2 The ionic conductivity of the second solid electrolyte 105 may be 0.01 mS / cm or more. 2 If the ratio is equal to or greater than this, the output characteristics of the battery can be improved.

[0140] The electrode compositions 1000 and 1001 may contain a conductive additive for the purpose of improving electronic conductivity. Examples of the conductive additive include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black and ketjen black, conductive fibers such as carbon fiber and metal fiber, conductive powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene. Using a carbon material as the conductive additive can reduce the cost of the electrode compositions 1000 and 1001.

[0141] The electrode composition 1000 may contain a dispersant for the purpose of improving the dispersibility of the coated active material 111. Similarly, the electrode composition 1001 may contain a dispersant for the purpose of improving the dispersibility of the coated active material 111 and the second solid electrolyte 105. The dispersant may be a low molecular weight dispersant or a polymeric dispersant. As the dispersant, for example, a commercially available dispersant, wetting agent, or surfactant may be used.

[0142] The electrode compositions 1000 and 1001 may contain an amine compound as a dispersant. The amine compound is suitable for improving the dispersibility of the solid electrolyte. Examples of the amine compound include aliphatic amines such as methylamine and dimethylamine, aromatic amines such as aniline, and heterocyclic amines such as imidazole and imidazoline.

[0143] The electrode compositions 1000 and 1001 may contain imidazoline or an imidazoline derivative as a dispersant. The imidazoline or imidazoline derivative is more suitable for improving the dispersibility of the active material and / or the solid electrolyte. Examples of imidazoline derivatives include 1-hydroxyethyl-2-alkenylimidazoline.

[0144] In the electrode composition 1001, the mass ratio of the second solid electrolyte 105 to the mass of the coated active material 111 is not particularly limited and may be, for example, 10 mass% or more and 150 mass% or less, for example, 20 mass% or more and 100 mass% or less, or 30 mass% or more and 70 mass% or less. When the mass ratio of the second solid electrolyte 105 is 10 mass% or more, the ionic conductivity of the electrode composition 1001 can be improved, and a high output battery can be achieved. When the mass ratio of the second solid electrolyte 105 is 150 mass% or less, a high energy density battery can be achieved.

[0145] The solid content (NV) of the electrode compositions 1000 and 1001 is determined appropriately depending on the particle size of the coated active material 111, the specific surface area of ​​the coated active material 111, the particle size of the second solid electrolyte 105, the specific surface area of ​​the second solid electrolyte 105, the type of solvent 104, and the type of binder 103. The solid content concentration of the electrode compositions 1000 and 1001 may be 40% by mass or more and 90% by mass or less, or 50% by mass or more and 80% by mass or less. By setting the solid content concentration to 40% by mass or more, the viscosity of the electrode compositions 1000 and 1001 can be increased, and sagging when the electrode compositions 1000 and 1001 are applied to a substrate can be suppressed. By setting the solid content concentration to 90% by mass or less, the wet film thickness when the electrode compositions 1000 and 1001 are applied to a substrate can be relatively thick, thereby enabling the production of an electrode sheet with a more uniform film thickness.

[0146] The fluidity of the electrode compositions 1000 and 1001 can be evaluated based on the viscosity ratio value measured using a viscosity / viscoelasticity measuring device. Alternatively, the fluidity of the electrode compositions 1000 and 1001 may be evaluated by evaluating the rheology using a viscosity / viscoelasticity measuring device.

[0147] The fluidity of the electrode compositions 1000 and 1001 can be evaluated, for example, by the following method. The viscosity of the electrode compositions 1000 and 1001 measured using a viscosity / viscoelasticity measuring device in rate control mode at 25°C and a shear rate of 1 / sec is defined as viscosity η1. The viscosity of the electrode compositions 1000 and 1001 measured using a viscosity / viscoelasticity measuring device in rate control mode at 25°C and a shear rate of 100 / sec is defined as viscosity η2. The fluidity of the electrode compositions 1000 and 1001 can be evaluated by the ratio η1 / η2 of viscosity η1 to viscosity η2.

[0148] In the electrode compositions 1000 and 1001, η / η may be 1.3 or more. By making η / η 1.3 or more, the dispersion stability of the electrode compositions 1000 and 1001 can be further improved. In addition, sagging of the electrode compositions 1000 and 1001 during application can be suppressed. The upper limit of η / η is, for example, 30. By making η / η 30 or less, the uniformity of the film thickness of the electrode sheet produced from the electrode compositions 1000 and 1001 can be improved.

[0149] Rheology may be evaluated to evaluate the fluidity of the electrode compositions 1000 and 1001. For example, the Casson yield value is used to evaluate the rheology.

[0150] The rheology of the electrode compositions 1000 and 1001 may be evaluated by the Casson yield value obtained in rate control mode using a viscosity / viscoelasticity measuring device. The Casson yield value can be calculated by the following method. First, the shear stress (S) of the electrode compositions 1000 and 1001 is measured using the viscosity / viscoelasticity measuring device at 25°C in rate control mode at shear rates (D) of 0.1 / sec to 1000 / sec. Using the obtained shear rate and shear stress values, the slope a and intercept b are determined based on the following relationship: The Casson yield value is the square of the intercept b in the following relationship:

[0151]

[0152] The electrode compositions 1000 and 1001 may have a Casson yield value of 0.05 Pa or more and 4.5 Pa or less. By setting the Casson yield value to 0.05 Pa or more, the electrode compositions 1000 and 1001 can be easily applied to a substrate. By setting the Casson yield value to 4.5 Pa or less, a coating film having a more uniform thickness can be produced.

[0153] Second Embodiment Hereinafter, a second embodiment will be described. Descriptions that overlap with the first embodiment will be omitted as appropriate.

[0154] A method for manufacturing an electrode sheet will be described below with reference to Fig. 4. Fig. 4 is a flowchart showing a method for manufacturing an electrode sheet. Here, as an example, a method for manufacturing an electrode sheet using the electrode composition shown in Fig. 1 is shown.

[0155] The electrode sheet manufacturing method may include steps S01, S02, S03, and S04. The electrode sheet manufacturing method includes applying the electrode composition 1000 to a current collector, a substrate, or an electrode assembly to form a coating film, and removing the solvent from the coating film. Steps S01 and S02 in FIG. 4 are described in the first embodiment. The electrode sheet manufacturing method includes step S03 of applying the electrode composition 1000 and step S04 of drying. Steps S01, S02, S03, and S04 may be performed in this order. Through these steps, an electrode sheet having a homogeneous and uniform thickness can be manufactured using the electrode composition 1000. In this way, the electrode sheet is obtained by applying and drying the electrode composition 1000. In other words, the electrode sheet is a solidified product of the electrode composition 1000.

[0156] In the electrode sheet manufacturing method, in the coating step S01, the active material 101 may be coated with the first solid electrolyte without the binder 103, and then in the kneading step S02, the binder 103 may be mixed with the coated active material 111. This manufacturing method can prevent the binder 103 from being disposed at the interface between the active material 101 and the first solid electrolyte, thereby improving the output characteristics of the battery. The mixing of the coated active material 111 and the binder 103 is performed, for example, by adding a styrene-based elastomer having a total nitrogen content of 30 ppm or more and 300 ppm or less to the coated active material.

[0157] 5 is a cross-sectional view of an electrode transfer sheet 2001 in embodiment 2. The electrode transfer sheet 2001 includes a substrate 202 and an electrode sheet 211 disposed on the substrate 202. The electrode transfer sheet 2001 can be manufactured by including, as step S03, a step of applying an electrode composition 1000 to the substrate 202.

[0158] 6 is a cross-sectional view of electrode 2002 in embodiment 2. Electrode 2002 includes current collector 203 and electrode sheet 201 placed on current collector 203. Electrode 2002 can be manufactured by including, as step S03, a step of applying electrode composition 1000 to current collector 203.

[0159] 7 is a cross-sectional view of a battery precursor 2003 in Embodiment 2. The battery precursor 2003 includes an electrode 2002, an electrolyte layer 302, and an electrode sheet 211. The electrolyte layer 302 is disposed on the electrode 2002. In addition, the electrode sheet 211 is disposed on the electrolyte layer 302. The electrode 2002 includes a current collector 203 and an electrode sheet 201 disposed on the current collector 203. The electrode assembly 2004 includes the electrode 2002 and a solid electrolyte layer 302 disposed on the electrode 2002.

[0160] In step S03, the electrode composition 1000 is applied to the substrate 202, the current collector 203, or the electrode assembly 2004. As a result, a coating film of the electrode composition 1000 is formed on the substrate 202, the current collector 203, or the electrode assembly 2004.

[0161] Examples of the coating method include die coating, gravure coating, doctor blade coating, bar coating, spray coating, electrostatic coating, etc. From the viewpoint of mass productivity, the die coating method may be used for coating.

[0162] Materials used for the substrate 202 include metal foil and resin film. Materials for the metal foil include copper (Cu), aluminum (Al), iron (Fe), nickel (Ni), and alloys thereof. Materials for the resin film include polyethylene terephthalate (PET), polyimide (PI), and polytetrafluoroethylene (PTFE). By applying the electrode composition 1000 to the substrate 202 and performing step S04, which will be described later, an electrode transfer sheet 2001 consisting of a laminate of the substrate 202 and the electrode sheet 211 is manufactured.

[0163] Examples of materials used for the current collector 203 include metal foil. Examples of materials for the metal foil include copper (Cu), aluminum (Al), iron (Fe), nickel (Ni), and alloys thereof. A coating layer made of the aforementioned conductive additive and binder may be provided on the surface of the metal foil. By applying the electrode composition 1000 to the current collector 203 and performing step S04 described below, an electrode 2002 made of a laminate of the current collector 203 and the electrode sheet 201 is manufactured.

[0164] The electrode assembly 2004 can be produced by forming the electrolyte layer 302 on the electrode 2002. The electrolyte layer 302 is formed by applying a solid electrolyte composition composed of a solid electrolyte, a binder, a solvent, etc. to the electrode 2002 and drying the composition to form the electrolyte layer 302 on the electrode 2002. Alternatively, the solid electrolyte composition is applied to a substrate and dried to produce a solid electrolyte sheet, and the solid electrolyte sheet is transferred to the electrode 2002 to form the electrolyte layer 302 on the electrode 2002. In this way, the electrode assembly 2004 is produced, which is a laminate of the electrode 2002 and the electrolyte layer 302.

[0165] In step S04, the applied electrode composition 1000 is dried. By drying the electrode composition 1000, for example, the solvent 104 is removed from the applied film of the electrode composition 1000, and the electrode sheet 201 is produced.

[0166] Examples of drying methods for removing the solvent 104 from the electrode composition 1000 include warm air / hot air drying, infrared heating drying, reduced pressure drying, vacuum drying, high frequency dielectric heating drying, and high frequency induction heating drying. These methods may be used alone or in combination of two or more.

[0167] The solvent 104 may be removed from the electrode composition 1000 by drying under reduced pressure. That is, the solvent 104 may be removed from the electrode composition 1000 in a pressure atmosphere lower than atmospheric pressure. The pressure atmosphere lower than atmospheric pressure may be, for example, −0.01 MPa or lower in gauge pressure. The drying under reduced pressure may be performed at a temperature of 50° C. or higher and 250° C. or lower.

[0168] The solvent 104 may be removed from the electrode composition 1000 by vacuum drying. That is, the solvent 104 may be removed from the electrode composition 1000 at a temperature lower than the boiling point of the solvent 104 and in an atmosphere at or below the equilibrium vapor pressure of the solvent 104.

[0169] From the viewpoint of manufacturing costs, the solvent 104 may be removed from the electrode composition 1000 by warm air or hot air drying. The set temperature of the warm air or hot air may be 50°C or higher and 250°C or lower, or 80°C or higher and 150°C or lower.

[0170] In step S04, the amount of solvent 104 removed from electrode composition 1000 can be adjusted by the drying method and conditions described above.

[0171] The removal of the solvent 104 can be confirmed by, for example, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), gas chromatography (GC), or gas chromatography mass spectrometry (GC / MS). Note that the solvent 104 does not have to be completely removed as long as the electrode sheet 201 after drying has ion conductivity. A portion of the solvent 104 may remain on the electrode sheet 201.

[0172] The battery precursor 2003 can be manufactured, for example, by combining the electrode 2002 with an electrode sheet 211 having a polarity opposite to that of the electrode 2002. That is, the active material contained in the electrode sheet 2001 is different from the active material contained in the electrode sheet 211. Specifically, when the active material contained in the electrode sheet 201 is a positive electrode active material, the active material contained in the electrode sheet 211 is a negative electrode active material. When the active material contained in the electrode sheet 201 is a negative electrode active material, the active material contained in the electrode sheet 211 is a positive electrode active material.

[0173] In the second embodiment, the electrode composition 1000 may be the electrode composition 1001 .

[0174] Third Embodiment Hereinafter, a third embodiment will be described. Descriptions that overlap with the first and second embodiments will be omitted as appropriate.

[0175] FIG. 8 is a cross-sectional view of a battery 3000 according to the third embodiment.

[0176] The battery 3000 in the third embodiment includes a positive electrode 301 , a negative electrode 303 , and an electrolyte layer 302 .

[0177] The electrolyte layer 302 is disposed between the positive electrode 301 and the negative electrode 303 .

[0178] The battery 3000 includes a positive electrode 301, an electrolyte layer 302, and a negative electrode 303 in this order.

[0179] Either the positive electrode 301 or the negative electrode 303 may include the electrode sheet 201 in the second embodiment.

[0180] The battery 3000 may include an electrode sheet 201 having a homogeneous and uniform thickness. Having a homogeneous and uniform thickness of the electrode sheet 201 means that the electrode sheet 201 has little variation in thickness. An electrode sheet 201 with little variation in thickness can have a thickness close to the design value at all positions within its surface. Therefore, even if the electrolyte layer 302 is made thinner, the possibility of contact (short circuit) between the positive electrode 301 and the negative electrode 303 can be reduced, thereby improving the energy density of the battery 3000. Furthermore, an electrode sheet 201 with excellent dispersibility of the active material and / or solid electrolyte tends to have excellent electronic conduction and / or ionic conduction within the electrode. Therefore, the output characteristics of the battery 3000 can be improved.

[0181] In the battery 3000, at least one selected from the group consisting of the positive electrode 301 and the negative electrode 303 may be the electrode 2002. The battery 3000 can be manufactured, for example, by combining the electrode 2002 with an electrode having a polarity opposite to that of the electrode 2002. This method is advantageous in terms of reducing the number of parts. When the electrode 2002 is a positive electrode, the electrode having a polarity opposite to that of the electrode 2002 is a negative electrode. When the electrode 2002 is a negative electrode, the electrode having a polarity opposite to that of the electrode 2002 is a positive electrode. The positive electrode or the negative electrode includes a current collector and an active material layer disposed on the current collector. A layer containing a solid electrolyte may be provided in the active material layer of the positive electrode or the active material layer of the negative electrode.

[0182] Methods for manufacturing the battery 3000 include a transfer method and a coating method. The transfer method is a method for manufacturing the battery 3000 using the electrode transfer sheet 2001. That is, the transfer method is a method for manufacturing the battery 3000 by preparing each component of the battery 3000 in a separate process and combining these components. The coating method is a method for manufacturing the battery 3000 that includes, for example, a method for directly forming a positive electrode or a negative electrode on an electrode assembly by applying an electrode composition to an electrode assembly in which an electrolyte layer is laminated on a positive electrode or a negative electrode, and drying the applied composition.

[0183] An example of a method for manufacturing the battery 3000 using the transfer method will be described below.

[0184] A manufacturing method for the battery 3000 includes, for example, applying the electrode composition 1000 to a substrate to form a coating film, removing the solvent from the coating film to form an electrode sheet 211, and transferring the electrode sheet 211 to the electrode assembly 2004. The battery 3000 is obtained by combining the electrode sheet 211 with the current collector 203 to form a second electrode. This results in the battery 3000 having a first electrode, an electrolyte layer, and a second electrode in this order. The electrode assembly 2004 includes an electrode 2002 and an electrolyte layer 302. The electrode 2002 is, for example, the first electrode.

[0185] A method for manufacturing the battery 3000 by a coating method will be described below.

[0186] The manufacturing method of the battery 3000 includes, for example, applying the electrode composition 1000 to the current collector 203 to form a coating film, and removing the solvent 104 from the coating film to form a first electrode. Additionally, the manufacturing method of the battery 3000 includes combining the first electrode, the second electrode, and the electrolyte layer 302 so that the electrolyte layer 302 is positioned between the first electrode and the second electrode. This results in the battery 3000 having the first electrode, the electrolyte layer, and the second electrode in this order. The battery 3000 is obtained by disposing the second electrode on the electrolyte layer 302. Methods for disposing the second electrode on the electrolyte layer 302 include applying the electrode composition 1000 to the electrolyte layer 302, transferring the electrode sheet 211 to the electrolyte layer 302, or joining the second electrode. When the first electrode is a positive electrode, the second electrode is a negative electrode. When the first electrode is a negative electrode, the second electrode is a positive electrode. Each of the first electrode and the second electrode includes, for example, a current collector and an active material layer disposed on the current collector. The active material layer of the first electrode or the active material layer of the second electrode may be provided with a layer containing a solid electrolyte.

[0187] The manufacturing method of the battery 3000 includes, for example, applying the electrode composition 1000 to the electrode assembly 2004 to form a coating film, and removing the solvent from the coating film to form the electrode sheet 211. The battery 3000 is obtained by combining the electrode sheet 201 with the current collector 203 to form a second electrode. This results in the battery 3000 having a first electrode, an electrolyte layer, and a second electrode in this order. The electrode assembly 2004 includes an electrode 2002 and an electrolyte layer 302. The electrode 2002 is, for example, the first electrode.

[0188] These coating methods are superior in terms of reducing the number of parts compared to the transfer method of transferring the electrode sheet 211 formed on the substrate 202. In other words, the above methods are superior in terms of mass productivity compared to the transfer method.

[0189] The battery 3000 may be manufactured by preparing a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are arranged in this order by the above-described method, and then pressure-molding the laminate at room temperature or at a high temperature using a press. Pressure-molding improves the filling of the coated active material 111, or the coated active material 111 and the second solid electrolyte 105, and enables the battery 3000 to achieve high output.

[0190] The battery 3000 may be manufactured by the following method. A negative electrode formed by laminating an electrode sheet (first negative electrode sheet) on a current collector, a first electrolyte layer, and a first positive electrode are arranged in this order. Meanwhile, an electrode sheet (second negative electrode sheet), a second electrolyte layer, and a second positive electrode are arranged in this order on the surface of the current collector opposite the surface on which the first negative electrode sheet is laminated. This results in a laminate in which the first positive electrode, the first electrolyte layer, the first negative electrode sheet, the current collector, the second negative electrode sheet, the second electrolyte layer, and the second positive electrode are arranged in this order. The battery 3000 may be manufactured by pressure molding this laminate at room temperature or at an elevated temperature using a press. This method makes it possible to manufacture a laminate of two batteries 3000 while suppressing warping of the battery, thereby enabling a high-output battery 3000 to be manufactured more efficiently. The order in which each component is laminated in the laminate is not particularly limited. For example, a stack of two batteries 3000 may be produced by placing a first negative electrode sheet and a second electrode sheet on a current collector, and then stacking a first electrolyte layer, a second electrolyte layer, a first positive electrode, and a second positive electrode in this order.

[0191] In the second embodiment, the electrode composition 1000 may be the electrode composition 1001 .

[0192] The electrolyte layer 302 is a layer containing an electrolyte material. Examples of the electrolyte material include a solid electrolyte. That is, the electrolyte layer 302 may be a solid electrolyte layer. The solid electrolyte contained in the electrolyte layer 302 may be any of the materials exemplified as the solid electrolyte in the first embodiment. Examples of the solid electrolyte that may be used include a sulfide solid electrolyte, an oxide solid electrolyte, a halide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte.

[0193] The electrolyte layer 302 may contain a solid electrolyte as a main component. The electrolyte layer 302 may contain the solid electrolyte in a mass ratio of 70% or more (70 mass % or more) relative to the entire electrolyte layer 302.

[0194] According to the above configuration, the output characteristics of the battery 3000 can be further improved.

[0195] The electrolyte layer 302 contains a solid electrolyte as a main component and may further contain unavoidable impurities, such as starting materials, by-products, and decomposition products used in synthesizing the solid electrolyte.

[0196] The electrolyte layer 302 may contain a solid electrolyte in a mass ratio of 100% relative to the entire electrolyte layer 302, excluding unavoidable impurities.

[0197] According to the above configuration, the output characteristics of the battery 3000 can be further improved.

[0198] The electrolyte layer 302 contains a solid electrolyte as a main component and may further contain unavoidable impurities, such as starting materials, by-products, and decomposition products used in synthesizing the solid electrolyte.

[0199] The electrolyte layer 302 may contain a solid electrolyte in a mass ratio of 100% relative to the entire electrolyte layer 302, excluding unavoidable impurities.

[0200] According to the above configuration, the output characteristics of the battery 3000 can be further improved.

[0201] The electrolyte layer 302 may contain two or more of the materials listed as solid electrolytes. For example, the electrolyte layer 302 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0202] The thickness of the electrolyte layer 302 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 302 is 1 μm or more, the possibility of short-circuiting between the positive electrode 301 and the negative electrode 303 is reduced. When the thickness of the electrolyte layer 302 is 300 μm or less, the battery 3000 can easily operate at high power. In other words, when the thickness of the electrolyte layer 302 is appropriately adjusted, the safety of the battery 3000 can be sufficiently ensured and the battery 3000 can be operated at high power.

[0203] The thickness of the solid electrolyte sheet included in the electrolyte layer 302 may be 1 μm or more and 30 μm or less, 1 μm or more and 15 μm or less, or 1 μm or more and 7.5 μm or less. When the thickness of the solid electrolyte sheet is 1 μm or more, the possibility of a short circuit between the positive electrode 301 and the negative electrode 303 is reduced. When the thickness of the solid electrolyte sheet is 30 μm or less, the internal resistance of the battery 3000 is reduced, thereby enabling high-power operation and improving the energy density of the battery 3000. The thickness of the solid electrolyte sheet is defined, for example, by the average value of multiple arbitrary points (e.g., three points) on a cross section parallel to the thickness direction.

[0204] The shape of the solid electrolyte contained in the battery 3000 is not particularly limited. The shape of the solid electrolyte may be needle-like, spherical, oval-spherical, etc. The shape of the solid electrolyte may also be particulate.

[0205] At least one selected from the group consisting of the positive electrode 301 and the negative electrode 303 may contain an electrolyte material, for example, a solid electrolyte. As the solid electrolyte, the solid electrolytes exemplified as materials constituting the electrolyte layer 302 can be used. With the above configuration, ionic conductivity (e.g., lithium ion conductivity) within the positive electrode 301 or the negative electrode 303 is improved, and the battery 3000 can operate at high output.

[0206] In the positive electrode 301 or the negative electrode 303, a sulfide solid electrolyte may be used as the solid electrolyte, and the above-mentioned halide solid electrolyte may be used as the coating material that coats the active material, or a halide solid electrolyte may be used as the solid electrolyte, and the above-mentioned sulfide solid electrolyte may be used as the coating material that coats the active material.

[0207] The positive electrode 301 includes, for example, a material having the property of absorbing and releasing metal ions (for example, lithium ions) as a positive electrode active material. The materials exemplified in Embodiment 1 can be used as the positive electrode active material.

[0208] When the solid electrolyte contained in the positive electrode 301 is in the form of particles (for example, spheres), the median diameter of the solid electrolyte may be 100 μm or less. When the median diameter of the solid electrolyte is 100 μm or less, the positive electrode active material and the solid electrolyte can be well dispersed in the positive electrode 301. This improves the charge / discharge characteristics of the battery 3000.

[0209] The median diameter of the solid electrolyte contained in the positive electrode 301 may be smaller than the median diameter of the positive electrode active material, thereby allowing the solid electrolyte and the positive electrode active material to be dispersed well.

[0210] The median diameter of the positive electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the positive electrode active material is 0.1 μm or more, the positive electrode active material and the solid electrolyte can be well dispersed in the positive electrode 301. As a result, the charge / discharge characteristics of the battery 3000 are improved. When the median diameter of the positive electrode active material is 100 μm or less, the lithium diffusion rate within the positive electrode active material is improved. Therefore, the battery 3000 can operate at high output.

[0211] In the positive electrode 301, the volume ratio "v1:100-v1" of the positive electrode active material to the solid electrolyte may satisfy 30≦v1≦95. v1 indicates the volume ratio of the positive electrode active material when the total volume of the positive electrode active material and solid electrolyte contained in the positive electrode 301 is taken as 100. When 30≦v1 is satisfied, it is easy to ensure a sufficient energy density for the battery 3000. When v1≦95 is satisfied, it is easy to operate the battery 3000 at high output.

[0212] The thickness of the positive electrode 301 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 301 is 10 μm or more, a sufficient energy density can be easily ensured for the battery 3000. When the thickness of the positive electrode 301 is 500 μm or less, the battery 3000 can more easily operate at high output.

[0213] When the positive electrode 301 includes an electrode sheet 201, the thickness of the electrode sheet 201 may be 10 μm or more and 500 μm or less, or 20 μm or more and 200 μm or less. When the thickness of the electrode sheet 201 is 10 μm or more, the energy density of the battery 3000 can be improved. When the thickness of the electrode sheet 201 is 500 μm or less, the internal resistance of the battery 3000 can be reduced, thereby enabling high-output operation. The thickness of the electrode sheet 201 is defined, for example, by the average value of multiple arbitrary points (e.g., three points) on a cross section parallel to the thickness direction.

[0214] The negative electrode 303 includes, for example, a material having a property of absorbing and releasing metal ions (for example, lithium ions) as a negative electrode active material. As the negative electrode active material, the materials exemplified in Embodiment 1 can be used.

[0215] The median diameter of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can be well dispersed in the negative electrode 303. This improves the charge / discharge characteristics of the battery 3000. When the median diameter of the negative electrode active material is 100 μm or less, the lithium diffusion rate within the negative electrode active material improves. This allows the battery 3000 to operate at high power.

[0216] The median diameter of the negative electrode active material may be larger than the median diameter of the solid electrolyte, which allows the solid electrolyte and the negative electrode active material to be dispersed well.

[0217] The volume ratio "v2:100-v2" of the negative electrode active material to the solid electrolyte contained in the negative electrode 303 may satisfy 30≦v2≦95. v2 indicates the volume ratio of the negative electrode active material when the total volume of the negative electrode active material and solid electrolyte contained in the negative electrode 303 is taken as 100. When 30≦v2 is satisfied, it is easy to ensure sufficient energy density for the battery 3000. When v2≦95 is satisfied, it is easy to operate the battery 3000 at high output.

[0218] The thickness of the negative electrode 303 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 303 is 10 μm or more, a sufficient energy density can be easily ensured for the battery 3000. When the thickness of the negative electrode 303 is 500 μm or less, the battery 3000 can more easily operate at high power.

[0219] When the negative electrode 303 includes the electrode sheet 201, the thickness of the electrode sheet 201 may be 10 μm or more and 500 μm or less, or 20 μm or more and 200 μm or less. When the thickness of the electrode sheet 201 is 10 μm or more, the energy density of the battery 3000 can be improved. When the thickness of the electrode sheet 201 is 500 μm or less, the internal resistance of the battery 3000 can be reduced, thereby enabling high-output operation. The thickness of the electrode sheet 201 is defined, for example, by the average value of multiple arbitrary points (e.g., three points) on a cross section parallel to the thickness direction.

[0220] The positive electrode active material and the negative electrode active material may be coated with a coating material to reduce the interfacial resistance between each active material and the solid electrolyte. A material with low electronic conductivity may be used as the coating material. Examples of the coating material include the oxide material, oxide solid electrolyte, halide solid electrolyte, and sulfide solid electrolyte exemplified in the first embodiment.

[0221] At least one selected from the group consisting of the positive electrode 301, the electrolyte layer 302, and the negative electrode 303 may contain a binder for the purpose of improving adhesion between particles. The materials exemplified in embodiment 1 can be used as the binder. When the binder contains an elastomer, each of the positive electrode 301, the electrolyte layer 302, and the negative electrode 303 included in the battery 3000 tends to have excellent flexibility and elasticity. In this case, the durability of the battery 3000 tends to be improved.

[0222] At least one selected from the group consisting of the positive electrode 301, the electrolyte layer 302, and the negative electrode 303 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid in order to facilitate the exchange of lithium ions and improve the output characteristics of the battery 3000.

[0223] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents that can be used include cyclic carbonate ester solvents, chain carbonate ester solvents, cyclic ether solvents, chain ether solvents, cyclic ester solvents, chain ester solvents, and fluorine solvents. Examples of cyclic carbonate ester solvents include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of chain carbonate ester solvents include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of cyclic ether solvents include tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane. Examples of chain ether solvents include 1,2-dimethoxyethane and 1,2-diethoxyethane. Examples of cyclic ester solvents include γ-butyrolactone. Examples of chain ester solvents include methyl acetate. Examples of fluorine-containing solvents include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, fluorodimethylene carbonate, etc. As the non-aqueous solvent, one non-aqueous solvent selected from these may be used alone, or a mixture of two or more non-aqueous solvents selected from these may be used.

[0224] The non-aqueous electrolyte may contain at least one fluorine solvent selected from the group consisting of fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, and fluorodimethylene carbonate.

[0225] Examples of lithium salts include LiPF, LiBF, LiSbF, LiAsF, LiSOCF, LiN(SOF), LiN(SOCF), LiN(SOCF), LiN(SOCF)(SOCF), and LiC(SOCF). A single lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt in the nonaqueous electrolyte may be 0.5 mol / L or more and 2 mol / L or less.

[0226] The gel electrolyte may be a polymer material containing a non-aqueous electrolyte, such as polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0227] The cations constituting the ionic liquid may be aliphatic chain quaternary cations such as tetraalkylammonium and tetraalkylphosphonium, aliphatic cyclic ammoniums such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperaziniums, and piperidiniums, and nitrogen-containing heterocyclic aromatic cations such as pyridiniums and imidazoliums. The anions constituting the ionic liquid may be PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2F)2 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , C(SO2CF3)3 - The ionic liquid may contain a lithium salt.

[0228] At least one selected from the group consisting of the positive electrode 301 and the negative electrode 303 may contain a conductive additive for the purpose of improving electronic conductivity. As the conductive additive, the materials exemplified in embodiment 1 can be used.

[0229] The battery 3000 may be a liquid battery containing an electrolyte solution. In this case, the electrolyte layer 302 may be a porous film made of a resin such as polyolefin. The positive electrode 301, the electrolyte layer 302, and the negative electrode 303 may each be impregnated with a nonaqueous electrolyte solution.

[0230] The shape of the battery 3000 may be a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, a laminated type, or the like.

[0231] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0232] (Technology 1) An electrode composition comprising: a solvent; a coated active material dispersed in the solvent; and a binder dispersed in the solvent, wherein the coated active material has an active material and a coating layer covering at least a portion of a surface of the active material, the coating layer including a first solid electrolyte, the first solid electrolyte including at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte, the binder including a styrene-based elastomer, and a total nitrogen content of the styrene-based elastomer being 30 ppm or more and 300 ppm or less.

[0233] According to the present disclosure, in the electrode composition, an appropriate interaction occurs between the coated active material and the binder, and this interaction can improve the fluidity of the electrode composition.

[0234] (Technology 2) The electrode composition according to Technology 1, wherein the first solid electrolyte includes a halide solid electrolyte, and the halide solid electrolyte includes Li, M, and X, wherein M is at least one selected from the group consisting of metal elements and semimetal elements other than Li, and X is at least one selected from the group consisting of F, Cl, Br, and I.

[0235] According to this configuration, the halide solid electrolyte does not contain sulfur, and therefore, generation of hydrogen sulfide gas can be suppressed.

[0236] (Technology 3) The electrode composition according to Technology 2, wherein M is at least one selected from the group consisting of Ca, Mg, Al, Y, Ti, and Zr. With this configuration, the halide solid electrolyte exhibits higher ionic conductivity, thereby enabling the battery to have higher output.

[0237] (Technology 4) The electrode composition according to Technology 3, wherein M is at least one selected from the group consisting of Al, Y, and Ti. With this configuration, the halide solid electrolyte exhibits higher ionic conductivity, thereby enabling the battery to have higher output.

[0238] (Technology 5) The electrode composition according to Technology 5, wherein the X includes F. According to this configuration, the halide solid electrolyte exhibits high electrochemical stability, and therefore, the cycle characteristics of the battery can be improved.

[0239] (Technology 6) The electrode composition according to claim 1, wherein the first solid electrolyte is represented by the following composition formula (1): Li α M β X γ ...Formula (1) Here, M is at least one selected from the group consisting of metal elements and metalloid elements other than Li, X is at least one selected from the group consisting of F, Cl, Br, and I, and α, β, and γ are each independent of one another and are values ​​greater than 0.

[0240] According to this configuration, the halide solid electrolyte exhibits high ionic conductivity, and therefore the battery can have a high output.

[0241] (Technology 7) The electrode composition according to Technology 1, wherein the first solid electrolyte includes a sulfide solid electrolyte. According to this configuration, the sulfide solid electrolyte exhibits high ionic conductivity, and therefore the battery can have high output.

[0242] (Technology 8) The electrode composition according to Technology 7, wherein the sulfide solid electrolyte contains Li2S-P2S5-based glass ceramics. According to this configuration, the Li2S-P2S5-based glass ceramics exhibit high ionic conductivity and are relatively soft materials, and therefore the battery can have a higher output.

[0243] (Technology 9) The electrode composition according to Technology 1, wherein the binder comprises at least one selected from the group consisting of modified SEBS and modified SBR. According to this configuration, the modified SEBS or modified SBR is particularly suitable as a binder for the electrode sheet because it has excellent flexibility and elasticity.

[0244] (Technology 10) The electrode composition according to Technology 1, wherein the boiling point of the solvent is 100° C. or higher and 250° C. or lower. According to this configuration, the solvent is unlikely to volatilize at room temperature, and therefore the electrode composition can be stably produced.

[0245] (Technology 11) The electrode composition according to Technology 1, wherein the solvent contains an aromatic hydrocarbon. According to this configuration, the binder tends to have high solubility in aromatic hydrocarbons. In particular, styrene-based elastomers are easily soluble in aromatic hydrocarbons. When the binder has high solubility in aromatic hydrocarbons, the dispersibility of the coated active material in the electrode composition can be further improved. Furthermore, because aromatic hydrocarbons have relatively low polarity, a decrease in ionic conductivity due to excessive adsorption and / or reaction with the solid electrolyte can be suppressed.

[0246] (Technology 12) The electrode composition according to Technology 1, wherein the solvent contains tetralin. According to this configuration, tetralin has a relatively high boiling point, and therefore not only improves the fluidity of the electrode composition but also enables the electrode composition to be stably produced by a kneading process.

[0247] (Technology 13) The electrode composition according to Technology 1, wherein the coating layer is composed of a plurality of layers. With this configuration, in a battery using an electrode sheet manufactured from the electrode composition, it is possible to achieve both improved cycle characteristics and improved output characteristics.

[0248] (Technology 14) The electrode composition according to Technology 1, further comprising a second solid electrolyte. With this configuration, the ionic conductivity of an electrode sheet produced from the electrode composition can be improved, and the output of a battery can be increased.

[0249] (Technology 15) The electrode composition according to any one of Techniques 1 to 14, wherein an outermost layer of the coating layer is composed of a layer containing the first solid electrolyte. According to this configuration, by providing the first solid electrolyte in the outermost layer which is likely to come into contact with the binder, the fluidity of the electrode composition can be further improved.

[0250] (Technology 16) A method for producing an electrode composition, comprising: coating an active material with a first solid electrolyte without using a binder to form a coated active material; and mixing a solvent, the coated active material, and a binder, wherein the coated active material has an active material and a coating layer that coats at least a portion of a surface of the active material, the coating layer comprising a first solid electrolyte, the first solid electrolyte comprising at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte, the binder comprising a styrene-based elastomer, and a total nitrogen content of the styrene-based elastomer being 30 ppm or more and 300 ppm or less.

[0251] This configuration allows the production of a battery with higher output characteristics, and also prevents the binder from being disposed at the interface between the active material and the first solid electrolyte, further improving the output characteristics of the battery.

[0252] (Technology 17) A method for producing an electrode composition, comprising: coating an active material with a first solid electrolyte without using a binder to form a coated active material; and mixing the coated active material with a styrene-based elastomer having a total nitrogen content of 30 ppm or more and 300 ppm or less.

[0253] This configuration can prevent the binder from being disposed at the interface between the active material and the first solid electrolyte, thereby improving the output characteristics of the battery.

[0254] (Technology 18) A method for producing an electrode sheet, comprising: applying the electrode composition according to Technology 1 to a substrate, a current collector, or an electrode assembly to form a coating film; and removing the solvent from the coating film.

[0255] According to this configuration, an electrode sheet having a uniform and even thickness can be manufactured.

[0256] (Technology 19) A method for manufacturing a battery having a first electrode, an electrolyte layer, and a second electrode in this order, the method comprising the following steps (i), (ii), or (iii): (i) applying the electrode composition described in Technology 1 to a substrate to form a coating film, removing the solvent from the coating film to form an electrode sheet for the second electrode, and combining the first electrode, the second electrode, and the electrolyte layer so that the electrolyte layer is located between the first electrode and the second electrode. (ii) applying the electrode composition described in Technology 1 to a current collector to form a coating film, removing the solvent from the coating film to form the first electrode, and combining the first electrode, the second electrode, and the electrolyte layer so that the electrolyte layer is located between the first electrode and the second electrode. (iii) applying the electrode composition described in Technology 1 to the electrolyte layer of an electrode assembly, which is a laminate of the first electrode and the electrolyte layer, to form a coating film, and removing the solvent from the coating film to form an electrode sheet for the second electrode.

[0257] Such a configuration allows the production of a battery with a higher energy density.

[0258] Hereinafter, the present disclosure will be described in detail using examples and comparative examples. Note that the electrode composition, electrode sheet, and battery of the present disclosure are not limited to the following examples.

[0259] Example 1-1 [Solvent] In all of the following steps, a commercially available dehydrated solvent or a solvent dehydrated by nitrogen bubbling was used as the solvent. The water content in the solvent was 10 ppm by mass or less.

[0260] [Preparation of Binder Solution] A binder solution was prepared by adding a solvent to a binder and dissolving or dispersing the binder in the solvent. The binder concentration in the binder solution was adjusted to 5% by mass or more and 10% by mass or less. Next, the binder solution was dehydrated by nitrogen bubbling until the water content reached 10 ppm by mass or less.

[0261] In Example 1-1, tetralin was used as the solvent for the binder solution. Solution-polymerized styrene-butadiene rubber (modified SBR) was used as the styrene-based elastomer constituting the binder. The modified SBR used was Asaprene (registered trademark) Y031 manufactured by Asahi Kasei Corporation. In the styrene-based elastomer constituting this binder, the molar fraction of repeating units derived from styrene was 0.16, and the weight-average molecular weight (Mw) of the binder was 380,000.

[0262] [Preparation of First Solid Electrolyte] In an argon glove box with a dew point of -60°C or less, raw material powders of LiF, TiF4, and AlF3 were weighed in a molar ratio of LiF:TiF4:AlF3 = 2.7:0.3:0.7. These were pulverized and mixed in a mortar to obtain a mixture. The mixture was milled using a planetary ball mill at 500 rpm for 12 hours. Then, a bead mill treatment was carried out. As a result, a halide solid electrolyte powder was obtained as the first solid electrolyte of Example 1. The halide solid electrolyte of Example 1 was prepared by mixing LiF, TiF4, and AlF3 in a molar ratio of 2.7:0.3:0.7. 2.7 Ti 0.3 Al 0.7 F6 (hereinafter referred to as "LTAF").

[0263] [Preparation of Coated Active Material] Powder of Li(NiCoAl)O2 (hereinafter referred to as "NCA") was prepared as a positive electrode active material. A coating layer composed of LTAF was formed on the surface of the NCA. The coating layer was formed by shearing using a particle mixer (BALANCE GRAN, manufactured by Freund Turbo). Specifically, NCA and LTAF were weighed to a mass ratio of 97.31:2.69, and processed at a rotation speed of 1000 rpm for a processing time of 135 minutes. No binder was added at this time. This resulted in the production of the coated active material of Example 1.

[0264] [Preparation of Electrode Composition] Tetralin and a binder solution were added to the coated active material in an argon glove box with a dew point of −60° C. or less. These materials were mixed at a mass ratio of coated active material:binder of 100:1.17, and the solid content (NV) was adjusted to 82. Next, the resulting mixture was kneaded using a planetary centrifugal mixer (ARE-310, manufactured by THINKY Corporation) at 1600 rpm for 3 minutes, thereby obtaining the electrode composition of Example 1.

[0265] Example 2 An electrode composition of Example 2 was prepared by the same method as Example 1, except that the styrene-based elastomer constituting the binder was a mixture containing a hydrogenated styrene-based thermoplastic elastomer (modified SEBS, manufactured by Asahi Kasei Corporation, Tuftec (registered trademark) MP10) and a hydrogenated block copolymer (SEBS, manufactured by Kraton Corporation, G1633) in a mass ratio of 2:3. In the styrene-based elastomer constituting the binder used in Example 2, the molar fraction of repeating units derived from styrene was 0.19, and the weight average molecular weight (Mw) of the binder was 270,000.

[0266] Example 3 An electrode composition of Example 3 was prepared by the same method as Example 1, except that a mixture containing a hydrogenated styrene-based thermoplastic elastomer (modified SEBS, manufactured by Asahi Kasei Corporation, Tuftec MP10) and a hydrogenated block copolymer (SEBS, manufactured by Kraton Corporation, G1633) in a mass ratio of 1:1 was used as the styrene-based elastomer constituting the binder. In the styrene-based elastomer constituting the binder used in Example 3, the molar fraction of repeating units derived from styrene was 0.19, and the weight average molecular weight (Mw) of the binder was 240,000.

[0267] Comparative Example 1 An electrode composition of Comparative Example 1 was prepared by the same method as in Example 1, except that solution-polymerized styrene-butadiene rubber (SBR, manufactured by Asahi Kasei Corporation, Tufden 2100R) was used as the styrene-based elastomer constituting the binder. In the styrene-based elastomer constituting the binder used in Comparative Example 1, the molar fraction of repeating units derived from styrene was 0.16, and the weight-average molecular weight (Mw) of the binder was 390,000.

[0268] Comparative Example 2 An electrode composition of Comparative Example 2 was prepared by the same method as in Example 1, except that the styrene-based elastomer constituting the binder was a mixture containing a hydrogenated styrene-based thermoplastic elastomer (modified SEBS, manufactured by Asahi Kasei Corporation, Tuftec MP10) and a hydrogenated block copolymer (SEBS, manufactured by Kraton Corporation, G1633) in a mass ratio of 7:3. In the styrene-based elastomer constituting the binder used in Comparative Example 2, the molar fraction of repeating units derived from styrene was 0.20, and the weight-average molecular weight (Mw) of the binder was 170,000.

[0269] Comparative Example 3 An electrode composition of Comparative Example 3 was prepared by the same method as in Example 1, except that the styrene-based elastomer constituting the binder was a mixture containing a hydrogenated styrene-based thermoplastic elastomer (modified SEBS, manufactured by Asahi Kasei Corporation, Tuftec MP10) and a hydrogenated block copolymer (SEBS, manufactured by Kraton Corporation, G1633) in a mass ratio of 4:1. In the styrene-based elastomer constituting the binder used in Comparative Example 3, the molar fraction of repeating units derived from styrene was 0.20, and the weight-average molecular weight (Mw) of the binder was 140,000.

[0270] Comparative Example 4 An electrode composition of Comparative Example 4 was prepared by the same method as in Example 1, except that a hydrogenated styrene-based thermoplastic elastomer (modified SEBS, manufactured by Asahi Kasei Corporation, Tuftec MP10) was used as the styrene-based elastomer constituting the binder. In the styrene-based elastomer constituting the binder used in Comparative Example 4, the molar fraction of repeating units derived from styrene was 0.20, and the weight average molecular weight (Mw) of the binder was 58,000.

[0271] Comparative Example 5 An electrode composition of Comparative Example 5 was prepared in the same manner as in Example 1, except that no binder was used.

[0272] Comparative Example 6 An electrode composition of Comparative Example 6 was prepared in the same manner as in Example 1, except that no coating layer was formed on the positive electrode active material.

[0273] [Measurement of total nitrogen content of styrene-based elastomer] The total nitrogen content of the styrene-based elastomer constituting the binder was measured by trace total nitrogen measurement using a trace total nitrogen analyzer (TN-2100H manufactured by Nitto Seiko Analytech Co., Ltd.) under the following measurement conditions.

[0274] [Measurement conditions] Temperature of pyrolysis furnace: 800°C Temperature of oxidation furnace: 900°C Carrier gas: O2 and Ar Standard sample: Pyridine / toluene solution Detector: Reduced pressure chemiluminescence detector

[0275] Under these measurement conditions, the mass (μg) of nitrogen (N) contained in 1 g of polymer was measured, and the total amount of nitrogen was calculated from the ratio (μg / g=ppm).

[0276] <Evaluation of Electrode Composition> The rheology of the electrode compositions of Examples 1 to 3 and Comparative Examples 1 to 6 was evaluated by the following method and under the following conditions.

[0277] [Evaluation of Fluidity] The fluidity of the electrode composition was evaluated in a dry room with a dew point of -40°C or less. A viscosity / viscoelasticity measuring device (HAAKE MARS40, manufactured by Thermo Fisher Scientific) and a cone plate with a diameter of 35 mm and an angle of 2° (C35 / 2 Ti, manufactured by Thermo Fisher Scientific) were used for the measurement. The viscosity of the electrode composition was measured at shear rates of 0.1 / sec to 1000 / sec under conditions of 25°C and rate control mode (CR mode). A flow curve was created by plotting the shear rate on the horizontal axis and the viscosity on the vertical axis. The behavior of the electrode composition was then evaluated based on the created flow curve using the above-mentioned criteria. In Table 1, a circle (○) indicates good fluidity. A cross (×) indicates poor fluidity.

[0278] [Calculation of Viscosity Ratio] The viscosity of the electrode composition was measured in a dry room with a dew point of -40°C or less. For the measurement, a viscosity / viscoelasticity measuring device (HAAKE MARS40, manufactured by Thermo Fisher Scientific) and a cone plate with a diameter of 35 mm and an angle of 2° (C35 / 2 Ti, manufactured by Thermo Fisher Scientific) were used. The viscosity of the electrode composition was measured at 25°C in rate control mode (CR mode) from a shear rate of 0.1 / sec to 1000 / sec, and the viscosity ratio η1 / η2 was calculated using the method described above.

[0279] [Measurement of Casson Yield Value] Rheology measurements of the electrode composition were carried out in a dry room with a dew point of -40°C or less. For the measurements, a viscosity / viscoelasticity measuring device (HAAKE MARS40, manufactured by Thermo Fisher Scientific) and a cone plate with a diameter of 35 mm and an angle of 2° (C35 / 2 Ti, manufactured by Thermo Fisher Scientific) were used. The shear stress of the electrode composition was measured at 25°C in rate control mode (CR) at shear rates from 0.1 / sec to 1000 / sec, and the Casson yield value was determined by the method described above.

[0280] The results of the above measurements are shown in Table 1 and Figures 9 and 10. Binder types A to G in Table 1 correspond to the following polymers, respectively. A: Solution-polymerized styrene-butadiene rubber (modified SBR), Asaprene Y031 B: Hydrogenated styrenic thermoplastic elastomer (amine-modified SEBS), a 2:3 mixture of Tuftec MP10, hydrogenated block copolymer (SEBS), and G1633 C: Hydrogenated styrenic thermoplastic elastomer (amine-modified SEBS), a 1:1 mixture of Tuftec MP10, hydrogenated block copolymer (SEBS), and G1633 D: Solution-polymerized styrene-butadiene rubber (SBR), Tufden 2100R E: Hydrogenated styrenic thermoplastic elastomer (amine-modified SEBS), a 7:3 mixture of Tuftec MP10, hydrogenated block copolymer (SEBS), and G1633 F: Hydrogenated styrenic thermoplastic elastomer (amine-modified SEBS), a 4:1 mixture of Tuftec MP10, hydrogenated block copolymer (SEBS), and G1633 G: Hydrogenated styrene-based thermoplastic elastomer (amine-modified SEBS), Tuftec MP10

[0281] It is presumed that Type A solution-polymerized styrene-butadiene rubber contains nitrogen components by substituting the terminals of the polymer with nitrogen-containing groups, while Type D solution-polymerized styrene-butadiene rubber contains nitrogen components as impurities separate from the polymer, which is the main component.

[0282] 9 and 10 are graphs in which the viscosity obtained in the evaluation of the fluidity of the electrode compositions in the examples and comparative examples is plotted against shear rate. FIG. 9 shows the results of Examples 1 to 3 and Comparative Examples 1 and 2. FIG. 10 shows the results of Example 1 and Comparative Examples 3 to 6. For the electrode compositions of Examples 1 to 3 and Comparative Examples 1 to 6, the fluidity was evaluated as "good (◯)" or "poor (×)" depending on whether the graph in which the viscosity was plotted against the shear rate resembled one of graphs A to D in FIG. 2.

[0283]

[0284] The electrode compositions of Examples 1 to 3 and Comparative Examples 1 to 4 all contained a coated active material and a styrene-based elastomer as a binder. As can be seen from Table 1 and Figures 9 and 10, the fluidity of the electrode compositions of Examples 1 to 3 was good. In Comparative Example 1, the total nitrogen content of the styrene-based elastomer in the electrode composition was low. Therefore, it is presumed that in Comparative Example 1, the binder was insufficiently adsorbed to the coated active material, resulting in poor fluidity of the electrode composition. In Comparative Examples 2 to 4, the total nitrogen content of the styrene-based elastomer was high. Therefore, it is presumed that in Comparative Examples 2 to 4, the binder was excessively adsorbed to the coated active material, resulting in poor fluidity of the electrode composition. In Comparative Example 5, the absence of a styrene-based elastomer is presumed to have resulted in poor fluidity of the electrode composition. In Comparative Example 6, the absence of a coating layer on the positive electrode active material is presumed to have resulted in poor fluidity of the electrode composition.

[0285] As can be seen from Table 1, the electrode compositions of the examples in which a coating layer of a first solid electrolyte was provided on the active material and a styrene-based elastomer having a nitrogen content of 30 ppm or more and 300 ppm or less was used as a binder were able to improve the fluidity of the electrode compositions.

[0286] The electrode composition, electrode sheet, and battery of the present disclosure can be used, for example, in the manufacture of a lithium ion secondary battery.

[0287] DESCRIPTION OF SYMBOLS 101 Active material 102 Coating layer 103 Binder 104 Solvent 105 Second solid electrolyte 111 Coated active material 112, 122 Ion conductor 201, 211 Electrode sheet 202 Substrate 203 Current collector 301 Positive electrode 302 Electrolyte layer 303 Negative electrode 1000, 1001 Electrode composition 2001 Electrode transfer sheet 2002 Electrode 2003 Battery precursor 2004 Electrode assembly 3000 Battery

Claims

1. An electrode composition comprising: a solvent; a coated active material dispersed in the solvent; and a binder dispersed in the solvent, wherein the coated active material has an active material and a coating layer coating at least a portion of a surface of the active material, the coating layer comprising a first solid electrolyte, the first solid electrolyte comprising at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte, the binder comprising a styrene-based elastomer, and a total nitrogen content of the styrene-based elastomer being 30 ppm or more and 300 ppm or less.

2. The electrode composition according to claim 1, wherein the first solid electrolyte comprises a halide solid electrolyte, the halide solid electrolyte comprises Li, M, and X, the M being at least one selected from the group consisting of metal elements and semi-metal elements other than Li, and the X being at least one selected from the group consisting of F, Cl, Br, and I.

3. The electrode composition according to claim 2, wherein M is at least one selected from the group consisting of Ca, Mg, Al, Y, Ti, and Zr.

4. The electrode composition according to claim 3, wherein M is at least one selected from the group consisting of Al, Y, and Ti.

5. The electrode composition according to claim 4, wherein X comprises F.

6. The electrode composition according to claim 1, wherein the first solid electrolyte is represented by the following composition formula (1): Li α M β X γ ...Formula (1) wherein, M is at least one selected from the group consisting of metal elements and metalloid elements other than Li, X is at least one selected from the group consisting of F, Cl, Br, and I, and α, β, and γ are each independent of one another and are values ​​greater than 0.

7. The electrode composition according to claim 1, wherein the first solid electrolyte comprises a sulfide solid electrolyte.

8. The electrode composition according to claim 7, wherein the sulfide solid electrolyte includes Li2S-P2S5-based glass ceramics.

9. The electrode composition according to claim 1, wherein the binder comprises at least one selected from the group consisting of modified SEBS and modified SBR.

10. The electrode composition according to claim 1, wherein the boiling point of the solvent is 100°C or higher and 250°C or lower.

11. The electrode composition of claim 1, wherein the solvent comprises an aromatic hydrocarbon.

12. The electrode composition according to claim 7, wherein the solvent comprises tetralin.

13. The electrode composition according to claim 1, wherein the coating layer is composed of multiple layers.

14. The electrode composition of claim 1, further comprising a second solid electrolyte.

15. An electrode composition according to any one of claims 1 to 14, wherein the outermost layer of the coating layer is composed of a layer containing the first solid electrolyte.

16. A method for producing an electrode composition comprising: coating an active material with a first solid electrolyte without using a binder to form a coated active material; and mixing a solvent, the coated active material, and a binder, wherein the coated active material has an active material and a coating layer coating at least a portion of a surface of the active material, the coating layer comprising a first solid electrolyte, the first solid electrolyte comprising at least one selected from the group consisting of a sulfide solid electrolyte and a halide solid electrolyte, the binder comprising a styrene-based elastomer, and a total nitrogen content of the styrene-based elastomer being 30 ppm or more and 300 ppm or less.

17. A method for producing an electrode composition comprising the steps of: coating an active material with a first solid electrolyte without using a binder to form a coated active material; and mixing the coated active material with a styrene-based elastomer having a total nitrogen content of 30 ppm or more and 300 ppm or less.

18. A method for producing an electrode sheet, comprising: applying the electrode composition according to claim 1 to a substrate, a current collector, or an electrode assembly to form a coating film; and removing the solvent from the coating film.

19. A method for manufacturing a battery comprising a first electrode, an electrolyte layer, and a second electrode in this order, comprising the steps of (i), (ii), or (iii) below: (i) applying the electrode composition according to claim 1 to a substrate to form a coating film; removing the solvent from the coating film to form an electrode sheet for the second electrode; and combining the first electrode, the second electrode, and the electrolyte layer such that the electrolyte layer is located between the first electrode and the second electrode; (ii) applying the electrode composition according to claim 1 to a current collector to form a coating film; removing the solvent from the coating film to form the first electrode; and combining the first electrode, the second electrode, and the electrolyte layer such that the electrolyte layer is located between the first electrode and the second electrode; (iii) applying the electrode composition according to claim 1 to the electrolyte layer of an electrode assembly which is a laminate of the first electrode and the electrolyte layer to form a coating film; and removing the solvent from the coating film to form an electrode sheet for the second electrode.

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