Moist powder and method for manufacturing nonaqueous electrolyte secondary battery having electrode made of the moist powder

Abstract

The present invention relates to a wet powder and a manufacturing method of a nonaqueous electrolyte secondary battery provided with an electrode composed of the wet powder. The wet powder disclosed herein is a wet powder for forming an electrode active material layer on an electrode current collector of either of a positive electrode and a negative electrode, composed of agglomerated particles containing an electrode active material and a nonaqueous electrolyte, and has a solid content rate of 70% or more when the entire wet powder is taken as 100% by mass, the nonaqueous electrolyte contains a nonaqueous solvent and a supporting salt, and the nonaqueous electrolyte has a viscosity of 25 mPa-S to 130 mPa-S at 25°C.

Description

Technical Field

[0001] The present invention relates to a wet powder and a method for producing a non-aqueous electrolyte secondary battery including an electrode composed of the wet powder. Background Art

[0002] Compared to existing batteries, secondary batteries such as lithium-ion secondary batteries are lightweight and have a higher energy density. Therefore, they are preferably used as high-output power supplies for vehicles or as power sources for personal computers and portable devices. In particular, lithium-ion secondary batteries are preferably used as high-output power supplies for driving vehicles such as battery-electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] The positive electrode and negative electrode (hereinafter referred to as "electrode" when there is no particular distinction between the positive and negative electrodes) of this secondary battery typically have a structure in which an electrode active material layer having an electrode active material as the main component is formed on one or both sides of a foil-shaped electrode collector. The electrode active material layer is prepared by dispersing solid components such as electrode active material, binder (adhesive), and conductive material in a predetermined solvent to prepare a slurry (paste) electrode material, applying the prepared slurry (paste) electrode material on the surface of the electrode collector to form a coating film, and after the coating film is dried, applying a pressing pressure to form a predetermined density and thickness. Alternatively, a study has been conducted to replace such film formation using composite slurry by using a so-called wet powder (Moisture Powder) in which a granular aggregate is formed in a state where the solvent is retained on the surface of the active material particles and the surface of the binder molecules.

[0004] Patent Document 1 discloses a wet composition comprising an active material, a binder, a solvent, and a surfactant, wherein the contact angle of the active material relative to a mixed liquid of the solvent and the surfactant is adjusted to 10° to 80°. It is disclosed that by using such a wet composition, a layer of electrode active material having a uniform thickness can be formed on a collector foil. Furthermore, Patent Document 2 discloses a method for manufacturing a secondary battery, including the step of manufacturing granules containing a portion of the solvent component of the electrolyte in order to suppress degradation of battery performance and improve the ductility of the granules.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-113113

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-117582 SUMMARY

[0009] In the past, solvents used in the production of such nonaqueous electrolyte secondary batteries, as described in Patent Document 2, have the possibility of reducing battery performance when remaining on the electrode and being carried into the battery. In addition, the binder resin that disperses in the solvent and binds the electrode active material to each other and the electrode active material layer to the current collector can become a resistance component when the electrode is constructed. Therefore, in order to reduce the resistance of the electrode, it is preferable to contain as little binder resin as possible. That is, the solvent and the binder resin are necessary materials during production, but on the other hand, can become an unnecessary component when the electrode is constructed, and therefore, it is preferable to contain as little (or, if possible, substantially no) binder resin as possible. Therefore, as the electrode material for constructing the electrode, a wet powder (electrode material) that contains substantially no binder resin and solvent is required.

[0010] The present application was made in view of the above-described circumstances, and the main object thereof is to provide a wet powder that can suppress a reduction in battery performance and increase the density of an electrode. In addition, another object thereof is to provide a method for producing a battery that has an electrode constructed from the wet powder.

[0011] In order to achieve the above-described object, a wet powder disclosed herein is provided. The wet powder disclosed herein is a wet powder for forming an electrode active material layer on an electrode current collector of either of a positive electrode and a negative electrode, and is composed of agglomerated particles that include an electrode active material and a nonaqueous electrolyte, and has a solid content ratio of 70% by mass or more when the entire wet powder is taken as 100% by mass. The above-described nonaqueous electrolyte contains a nonaqueous solvent and a supporting salt, and the viscosity of the above-described nonaqueous electrolyte at 25°C is 25 mPa-S to 130 mPa-S.

[0012] The nonaqueous electrolyte does not have concerns about adversely affecting battery performance, and by adjusting such a nonaqueous electrolyte to be high in viscosity and using it as a liquid component, a wet powder that is bound by liquid cross-linking force even if it contains substantially no binder resin that can become a resistance component and no solvent that has concerns about adversely affecting battery performance can be provided. According to this configuration, a wet powder that can suppress a reduction in battery performance and increase the density of an electrode can be achieved.

[0013] One preferable mode of the wet powder disclosed herein is characterized in that, in the above-described agglomerated particles, a solid phase and a liquid phase form a capillary state.

[0014] In the agglomerated particles that constitute the wet powder, by forming the capillary state described below in the solid phase and the liquid phase, a wet powder that can more appropriately form an electrode can be provided.

[0015] In a preferred embodiment of the wet powder disclosed herein, the non-aqueous solvent comprises at least one member selected from the group consisting of ethers, carbonates, glymes, esters, carbamates, amides, sulfides, sulfoxides, sulfones, and ketones, and the viscosity of the non-aqueous solvent at 25°C is 0.6 mPa·s to 4.1 mPa·s. In another preferred embodiment, the non-aqueous solvent comprises at least the carbonates and glymes, and the non-aqueous electrolyte solution contains 30 vol% or more of the glymes, based on 100 vol%.

[0016] According to the nonaqueous solvent having the above-described structure, the viscosity of the nonaqueous electrolyte solution that can be contained as a liquid component in the wet powder can be appropriately adjusted, and the liquid crosslinking force of the wet powder can be appropriately controlled.

[0017] In a preferred embodiment of the wet powder disclosed herein, the concentration of the supporting salt in the non-aqueous electrolyte is 2 mol / L to 5 mol / L.

[0018] According to the above configuration, the viscosity of the non-aqueous electrolyte solution contained in the wet powder can be appropriately adjusted.

[0019] In order to achieve the other objectives described above, a method for manufacturing a non-aqueous electrolyte secondary battery disclosed herein can be provided. The manufacturing method disclosed herein is a method for manufacturing a non-aqueous electrolyte secondary battery having an electrode body having a positive electrode and a negative electrode, and a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt, comprising the following steps: a step of granulating a wet powder formed from aggregated particles containing at least an electrode active material and the non-aqueous electrolyte; a step of supplying an electrode active material layer composed of the wet powder to an electrode current collector to form an electrode; a step of housing the electrode body produced using the electrode in a battery case; and a step of injecting the non-aqueous solvent into the battery case housing the electrode body. Here, the method for manufacturing a non-aqueous electrolyte secondary battery is characterized in that the viscosity of the non-aqueous electrolyte at 25°C in the granulation step is adjusted to 25 mPa·S to 130 mPa·S.

[0020] According to the above-mentioned formation, owing to not containing the solvent of the concern that battery performance is caused to have a negative impact in fact, therefore, can manufacture the battery that electrode density is improved under the situation that does not possess the operation of removing this solvent, equipment.In addition, owing to make the nonaqueous electrolyte that comprises supporting salt be contained in the electrode in advance in the granulation process, therefore, in the nonaqueous solvent injection process, compared with the past, only injecting a small amount of nonaqueous solvent is enough.Thus, the time of injection process is shortened, does not contain supporting salt, therefore, the preservation property of nonaqueous solvent becomes higher.That is, as mentioned above, can suppress the secondary battery that manufactures the electrode that battery performance is improved in production cost.

[0021] In a preferred embodiment of the production method disclosed herein, the concentration of the support salt in the nonaqueous electrolyte in the granulation step is 2 to 5 mol / L.

[0022] According to the above configuration, the viscosity of the nonaqueous electrolyte in the granulation step can be appropriately adjusted.

[0023] In a preferred embodiment of the production method disclosed herein, the electrode formation step forms the electrode by causing the wet powder supplied between the first roller and the second roller to adhere to the outer peripheral surface of the second roller as the electrode active material layer, and transferring the electrode active material layer from the outer peripheral surface of the second roller to the surface of the electrode current collector supplied to the second roller, wherein the second roller is disposed opposite the first roller.

[0024] According to the above configuration, the wet powder granulated in the granulation step can be favorably transferred to the electrode current collector. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a flowchart showing the general procedure of the electrode production method of one embodiment.

[0026] Figure 2 is an explanatory diagram schematically showing the presence form of the solid phase (active material particles and the like solid components), the liquid phase (solvent), and the gas phase (voids) of the agglomerated particles constituting the wet powder, (A) shows a pendular state, (B) shows a funicular state, (C) shows a capillary state, and (D) shows a slurry state.

[0027] Figure 3 is an explanatory diagram schematically showing the configuration of the roll film formation apparatus of one embodiment.

[0028] Figure 4 is an explanatory diagram schematically showing a lithium-ion secondary battery of one embodiment.

[0029] SYMBOLS

[0030] 1 Agglomerated particle

[0031] 2 Solid component (solid phase)

[0032] 3 Liquid component (liquid phase)

[0033] 4 Void (gas phase)

[0034] 20 Wet powder

[0035] 31 Electrode current collector

[0036] 32 electrode active material layer

[0037] 40 roll film forming device

[0038] 41 first rotating roll (supply roll)

[0039] 42 second rotating roll (transfer roll)

[0040] 43 support roll

[0041] 45 partition wall

[0042] 50 battery case

[0043] 52 positive electrode terminal

[0044] 52a positive electrode current collector

[0045] 54 negative electrode terminal

[0046] 54a negative electrode current collector

[0047] 56 safety valve

[0048] 60 positive electrode sheet

[0049] 62 positive electrode current collector

[0050] 64 positive electrode active material layer

[0051] 66 positive electrode active material layer non-forming portion

[0052] 70 negative electrode sheet

[0053] 72 negative electrode current collector

[0054] 74 negative electrode active material layer

[0055] 76 negative electrode active material layer non-forming portion

[0056] 80 jelly-roll electrode body

[0057] 90 spacer

[0058] 100 lithium ion secondary battery DETAILED DESCRIPTION

[0059] Hereinafter, the wet powder and the manufacturing method of the battery having the electrode composed of the wet powder, which are disclosed herein, will be described in detail, taking an electrode which can be appropriately used in a lithium ion secondary battery as a typical example of a secondary battery.

[0060] Matters other than those not specifically mentioned in the present specification and matters required for implementation can be understood as matters of design for those skilled in the art based on the existing technology in the field. The technical contents disclosed herein can be implemented based on the contents disclosed in the present specification and the technical common sense in the field.

[0061] In addition, dimensional relationships (length, width, height, etc.) do not reflect actual dimensional relationships.

[0062] Note that in the present specification, the expression "A to B (where A, B are arbitrary values)" indicating a range means A or more and B or less.

[0063] In the present specification, "secondary battery" means a general battery capable of repeated charging. In addition, "nonaqueous electrolyte secondary battery" means a battery provided with a nonaqueous electrolyte (typically, a nonaqueous electrolyte containing a supporting electrolyte in a nonaqueous solvent). "Lithium ion secondary battery" means a secondary battery that utilizes lithium ions as charge carriers and realizes charging and discharging by movement of charges of lithium ions between positive and negative electrodes. In addition, in the present specification, when it is not necessary to particularly distinguish between positive and negative electrodes, it is simply referred to as an electrode.

[0064] The wet powder disclosed herein is typically composed of agglomerated particles containing an electrode active material and a nonaqueous electrolyte. The solid content rate when the entire wet powder is taken as 100 mass% is typically 70 mass% or more. For example, it can be 70 mass% to 87 mass%, or it can be 72 mass% to 85 mass%. The wet powder disclosed herein is set to a relatively high value in terms of the solid content rate compared to the slurry-like composition of the past. By setting the solid content rate within the above range, the capillary state described later is appropriately formed in the agglomerated particles, and even in a manner that substantially does not contain a binder resin and a solvent, the electrode active material can be appropriately integrated by the liquid cross-linking force (the sum of the capillary negative pressure and the surface tension).

[0065] Note that in the present specification, "solid content rate" means the proportion of solid content in the entire wet powder.

[0066] The wet powder disclosed herein is in a powder shape as a whole, and is in a state where a free liquid surface in which a gas-liquid interface is not present. As a powder exhibiting such a property, for example, it is preferable that the agglomerated particles constituting the wet powder form the capillary state described later.

[0067] Regarding the morphological classification of the wet powders, the present description adopts the four commonly known classifications described in "Particle Size Enlargement" by Capes CE (published by Elsevier Scientific Publishing Company, 1980), and the wet powders disclosed herein are clearly defined as follows.

[0068] Generally speaking, the existence forms (filling states) of the solid phase (solid components such as electrode active materials), liquid phase (liquid components such as non-aqueous electrolyte) and gas phase (voids) of agglomerated particles can be classified into four types: "pendulum state", "ribbon state", "capillary state" and "mud state".

[0069] like Figure 2 As shown in (A), the "pendulum state" is a state in which the liquid component (liquid phase) 3 exists discontinuously by cross-linking the solid components (solid phase) 2 in the aggregated particles 1, while the solid components 2 can exist in a connected (continuous) state. As shown in the figure, the content of the liquid component 3 is relatively low. As a result, the voids (gas phase) 4 present in the aggregated particles 1 are mostly continuous, forming interconnected pores leading to the outside.

[0070] In addition, if Figure 2 As shown in (B), the "cord state" is a state in which the content of liquid component 3 in the aggregated particle 1 is relatively high compared to the pendulum state, resulting in a state in which the liquid component 3 exists continuously around the solid component 2 in the aggregated particle 1. However, the amount of liquid component 3 is still small, so, similar to the pendulum state, the solid component 2 exists in a connected (continuous) state. Although there is a trend that the proportion of communicating pores leading to the outside in the voids 4 in the aggregated particle 1 is slightly reduced, and the proportion of discontinuous isolated voids is increased, the presence of communicating pores is confirmed.

[0071] like Figure 2 As shown in (C), the "capillary state" is when the content of the liquid component 3 in the condensed particles 1 increases, the amount of the liquid component 3 in the condensed particles 1 approaches the saturated state, and a sufficient amount of the liquid component 3 exists continuously around the solid component 2. As a result, the solid component 2 exists in a discontinuous state. The solid components are filled with the liquid component 3, and the binding force between the solid components is strong. By the liquid component 3 staying on the surface of the condensed particles 1, the surface of the condensed particles 1 is in a wet state, and becomes a state where viscosity can be exerted. By increasing the content of the liquid component 3 in the condensed particles 1, there are almost no voids. When voids exist, almost all of them (for example, more than 80 vol% of the total void volume) exist in the form of isolated voids.

[0072] likeFigure 2 "mud state" is a state in which the solid component 2 has been suspended in the liquid component 3, becoming a state that cannot be called a coacervate particle. It is a state further lacking a gas phase compared to the capillary state.

[0073] As the main component of the solid component 2, i.e., the electrode active material, a compound of a composition employed as a negative electrode active material or a positive electrode active material of a conventional secondary battery (here, a lithium-ion secondary battery) can be used. For example, as the negative electrode active material, carbon materials such as graphite, hard carbon, and soft carbon can be given. In addition, as other examples of the negative electrode active material, metal materials (so-called alloy-based negative electrodes) composed of metals such as tin (Sn), aluminum (Al), zinc (Zn), and silicon (Si) or alloys in which these metals are the main component can be given. As the positive electrode active material, lithium transition metal complex oxides such as LiMn2O4, LiNiO2, LiCoO2, LiFeO2, LiNi0.5Mn1.5O4, and LiMnO2, and lithium transition metal phosphoric acid compounds such as LiFePO4 can be given. The average particle diameter of the electrode active material is not particularly limited, and it is appropriate to be about 0.1 μm to 50 μm, and it is preferably about 1 to 20 μm. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, and LiMnO2, and lithium transition metal phosphoric acid compounds such as LiFePO4. The average particle diameter of the electrode active material is not particularly limited, and it is appropriate to be about 0.1 μm to 50 μm, and it is preferably about 1 to 20 μm.

[0074] Note that, in the present specification, the "average particle diameter" means a particle diameter (D 50 (also called a median particle diameter)) corresponding to a cumulative frequency of 50% by volume from the fine particle side in a particle size distribution based on a volume basis of a general laser diffraction-light scattering method.

[0075] As the other solid component 2, for example, electrically conductive materials and the like can be given. As the electrically conductive material, for example, carbon black such as acetylene black (AB) and other (graphite and the like) carbon materials can be preferably used.

[0076] The wet powder disclosed herein is substantially free of the binder resin used in the conventional electrode manufacturing method. The binder resin referred to herein is a resin that has a binding action but does not have an electrically conductive property, and examples thereof include rubber-based resins such as styrene butadiene copolymer (SBR), acrylic-modified SBR resin (SBR-based latex), cellulose-based polymers such as carboxymethyl cellulose (CMC), acrylic-based resins such as polymers of methacrylate, and polyvinylidene fluoride (PVdF). The binder resin described above is a component that has been used in the conventional electrode material to bind active materials to each other and to bind the electrode material to the electrode current collector, and is a necessary component. However, the binder resin generally becomes a resistance component when the electrode is constructed, and therefore it is preferable to have as little (or substantially none, if possible) of the binder resin as possible. By being substantially free of the binder resin, the density of the electrode active material (the electrode density) can be increased.

[0077] Note that, in the present specification, "substantially free of" means that the subject component is not intentionally added, and means that the component is completely free of the component or that the manufacturing method disclosed herein contains only an extremely small amount (so-called contamination level) that has no meaning.

[0078] In addition, the wet powder disclosed herein is substantially free of the solvent used in the conventional electrode manufacturing method. The solvent referred to herein is a liquid component that is considered to have an adverse effect on the performance of the battery when the secondary battery is constructed, and examples thereof include N-methyl-2-pyrrolidone (NMP), water-based solvents (water or a mixed solvent mainly composed of water), and the like. The solvent described above is used as a necessary component in the conventional manufacturing method for the purpose of appropriately dispersing the active material, the electrically conductive material, and the like. However, if the solvent remains when the electrode is constructed, it has an adverse effect on the performance of the battery, and therefore it is necessary to remove the solvent by drying or the like. In contrast, in the wet powder disclosed herein, the conventional solvent is substantially free, and a nonaqueous electrolyte that does not have an adverse effect on the performance of the battery when the secondary battery is constructed is used. Therefore, it is possible to provide a wet powder that can construct a secondary battery of higher quality.

[0079] As the nonaqueous electrolyte contained in the wet powder, a nonaqueous electrolyte containing a supporting electrolyte (also referred to as a supporting salt) in a nonaqueous solvent can be typically used. The nonaqueous electrolyte is required to have a higher viscosity than the conventional electrolyte. Specifically, it is a nonaqueous electrolyte having a viscosity (shear viscosity) of 25 mPa s or more at 25°C. The viscosity of the nonaqueous electrolyte can be 25 mPa s or more and 130 mPa s or less, or 50 mPa s or more and 122 mPa s or less. According to the above configuration, liquid cross-linking force can be appropriately exerted between solid components, and an electrode active material layer having an increased electrode density can be formed.

[0080] Note that the viscosity here refers to shear viscosity (mPa-s) and can be easily measured using a commercially available rotational viscometer (e.g., the well-known B-type viscometer of Brookfield).

[0081] As the type of nonaqueous solvent, for example, ethers, carbonates, esters, carbamates, amides, sulfides, sulfoxides, sulfones, ketones, glyme dimethyl ethers, and the like can be given. Among these, in order to easily produce a nonaqueous electrolyte solution having a high viscosity, carbonates and / or glyme dimethyl ethers can be preferably used. Specifically, ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC), triglyme dimethyl ether (G3), tetraglyme dimethyl ether (G4), and the like can be given. Such a nonaqueous solvent can be used alone as one kind or can be used in combination of two or more as appropriate.

[0082] Note that glyme dimethyl ether refers to a general term for linear glyme diethers. Triglyme dimethyl ether (triethylene glycol dimethyl ether) refers to an ether compound represented by the structural formula of CH3(OCH2CH2)3OCH3. Further, tetraglyme dimethyl ether (tetraethylene glycol dimethyl ether) refers to an ether compound represented by the structural formula of CH3(OCH2CH2)4OCH3.

[0083] In a preferable embodiment, the nonaqueous solvent has a viscosity of 0.6 mPa-s to 4.1 mPa-s, or 0.6 mPa-s to 3.8 mPa-s at 25°C. The above-mentioned viscosity can be adjusted to the above-mentioned appropriate viscosity range by using one kind of the above-mentioned nonaqueous solvent having an appropriate viscosity alone or by combining two or more as appropriate. When two or more are combined, the nonaqueous solvent as a whole is preferably composed of 30 vol% or more (e.g., 30 to 50 vol%) of the above-mentioned glyme dimethyl ethers.

[0084] As the supporting salt contained in the nonaqueous solvent, a conventional supporting salt used in a nonaqueous electrolyte secondary battery can be used without particular limitation. For example, lithium salts such as LiPF6, LiBF4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, and the like can be used.

[0085] The concentration of the supporting salt in the nonaqueous electrolyte is adjusted so that the viscosity of the nonaqueous electrolyte becomes the above-mentioned range. Generally, the viscosity of the nonaqueous electrolyte can be increased by increasing the concentration of the supporting salt in the nonaqueous electrolyte. This varies depending on the nonaqueous solvent used, and thus is not particularly limited, and for example, is preferably 2 mol / L to 5 mol / L, more preferably 2 mol / L to 4.5 mol / L, and particularly preferably 2.5 mol / L to 4.1 mol / L.

[0086] The concentration of the supporting salt in the nonaqueous electrolyte used in the conventional nonaqueous electrolyte secondary battery is typically approximately 1 mol / L. In the nonaqueous solvent injection process described later, the nonaqueous solvent is injected, and the concentration of the supporting salt can be adjusted so that it becomes approximately 1 mol / L (for example, 0.7 mol / L to 1.3 mol / L). Thus, the concentration of the supporting salt in the nonaqueous electrolyte in the wet powder (electrode material) can be higher than in the conventional case. By setting the concentration of the supporting salt to be higher, the viscosity of the nonaqueous electrolyte becomes higher, and the moldability in the electrode formation process described later is improved.

[0087] Note that the nonaqueous electrolyte of the nonaqueous secondary battery of the present embodiment can contain various additives such as a gas generating agent such as biphenyl (BP) or cyclohexylbenzene (CHB), a coating forming agent, a dispersant, a thickening agent, and the like, without significantly impairing the effects of the present application.

[0088] <Method for manufacturing nonaqueous electrolyte secondary battery>

[0089] Figure 1 is a flowchart showing the electrode manufacturing method disclosed herein. The electrode manufacturing method disclosed herein typically includes the following four processes: (1) a process of granulating a wet powder (S110); (2) a process of forming an electrode (S120); (3) a process of housing an electrode body produced from the electrode in a battery case (S130); and (4) a process of injecting a nonaqueous solvent (S140). Hereinafter, each process will be described in detail.

[0090] <Granulation process>

[0091] In the granulation process S110, the electrode active material and the nonaqueous electrolyte are mixed and then granulated, and the electrode material in a wet state (wet powder) is granulated. The method of mixing is not particularly limited, and for example, a mixer such as a planetary mixer can be used for mixing. As a method of producing granulated particles, for example, there are a tumbling granulation method, a fluidized bed granulation method, a stirring granulation method, a compression granulation method, an extrusion granulation method, a crushing granulation method, a spray drying method, and the like. Among these, the compression granulation method is suitable for granulating the wet powder disclosed herein, and thus is preferred.

[0092] First, the electrode active material and the non-aqueous electrolyte are mixed using a mixer such as a planetary mixer. The mixer typically comprises: a cylindrical mixing container, a rotating blade housed inside the mixing container, and a motor connected to the rotating blade via a rotating shaft. The electrode active material and the non-aqueous electrolyte are added to the mixing container of the mixer, and the mixture is rotated at a speed of, for example, 2000 rpm to 5000 rpm for 1 to 30 seconds to produce a mixture of the electrode active material and the non-aqueous electrolyte. The non-aqueous electrolyte is measured and added in such a way that the solid content of the wet powder becomes 70% by mass or more, more preferably 75% by mass or more (for example, 80 to 87% by mass). Next, the conductive material is added to the mixing container, and the rotating blade is further rotated at a speed of, for example, 100 rpm to 1000 rpm for 1 to 30 seconds. Thus, a mixture in a wet state in which each material is fully mixed can be obtained.

[0093] Next, the mixture is compressed and granulated using a conventionally known granulation apparatus. For example, a preferred embodiment of this granulation apparatus includes a roller mill, which compresses and granulates the mixture by feeding it between a pair of rollers rotating in opposite directions. In compression granulation using a roller mill, high compressive and shearing forces are applied to the fed mixture while granulating it. While not particularly limited, it is speculated that the above granulation method, when performed as described below, can appropriately form a wet powder in a capillary state.

[0094] The wet powder disclosed herein contains a high-viscosity non-aqueous electrolyte. The high-viscosity non-aqueous electrolyte is properly attached to the surface of the solid material (here, the electrode active material) by the above-mentioned mixing. By compressing and rubbing the electrode active materials against each other in such a state, gas is squeezed out from the mixture, and the electrode active materials can be in a state of higher density. That is, it is possible to properly form a Figure 2 (C) shows capillary aggregated particles 1. Electrode active materials can be strongly bound to each other by liquid crosslinking forces. Furthermore, the use of a high-viscosity nonaqueous electrolyte can further enhance the binding strength of aggregated particles 1. This allows wet powders to be granulated even without a binder resin that could potentially act as a resistive component.

[0095] The properties of the wet powder granulated in the granulation step may be, for example, an average particle size of approximately 10 μm or more, 100 μm or more, or 1 mm or more. The upper limit of the average particle size is not particularly limited, but typically may be 10 mm or less, for example, 5 mm or less.

[0096] <Electrode Formation Process>

[0097] The electrode forming step S120 is a step of supplying the electrode active material layer composed of the wet powder to the electrode current collector to form the electrode. The electrode active material layer 32 composed of the wet powder 20 can be formed using the schematic diagram shown in FIG. Figure 3 Such a roll film forming device 40 is performed. As shown in the drawings, the roll film forming device 40 includes a first rotating roller 41 (hereinafter also referred to as "supply roller 41") and a second rotating roller 42 (hereinafter also referred to as "transfer roller 42") arranged opposite to the first rotating roller 41. The outer peripheral surface of the supply roller 41 and the outer peripheral surface of the transfer roller 42 are opposite to each other. The pair of rotating rollers 41 and 42 are as shown in FIG. Figure 3 As shown by the arrows, the feed roller 41 and the transfer roller 42 can rotate in opposite directions. In addition, the gap between the feed roller 41 and the transfer roller 42 can be separated by only a distance corresponding to the desired thickness of the electrode active material layer 32 formed on the long sheet-shaped electrode current collector 31. In addition, by adjusting the size of the gap, it is also possible to adjust the force that compresses the wet powder 20 passing between the feed roller 41 and the transfer roller 42. Therefore, by adjusting the size of the gap between the feed roller 41 and the transfer roller 42 according to the solid content of the wet powder 20, etc., the granulated particles are appropriately integrated with each other, stretched, and formed into a film.

[0098] The electrode collector 31 can use, without particular limitation, any metal electrode collector used as the electrode collector of this type of secondary battery. When the electrode collector 31 is a positive electrode collector, for example, it is made of a metal material having good electrical conductivity, such as aluminum, nickel, titanium, stainless steel, etc. Aluminum (for example, aluminum foil) is particularly preferred. When the electrode collector 31 is a negative electrode collector, for example, it is made of a metal material having good electrical conductivity, such as copper, an alloy mainly composed of copper, nickel, titanium, stainless steel, etc. Copper (for example, copper foil) is particularly preferred. The thickness of the electrode collector 31 is, for example, approximately 5 μm to 20 μm, preferably 8 μm to 15 μm.

[0099] Partition walls 45 are provided at both ends of the supply roller 41 and the transfer roller 42 in the width direction. The partition walls 45 hold the wet powder 20 on the supply roller 41 and the transfer roller 42, and the distance between the two partition walls 45 defines the width of the electrode active material layer 32 formed on the electrode current collector 31. The electrode material (wet powder 20) is supplied between the two partition walls 45 by a feeder (not shown) or the like.

[0100] In the roll film forming device 40 of this embodiment, a support roller 43 is arranged as a third rotating roller next to the transfer roller 42. The support roller 43 plays a role in conveying the electrode collector 31 to the transfer roller 42. The transfer roller 42 and the support roller 43 are as follows: Figure 3 The arrows rotate in opposite directions.

[0101] The supply roller 41, the transfer roller 42, and the support roller 43 are connected to independent driving devices (motors) not shown, respectively, and the wet powder 20 is transported along the transfer roller 42 and transferred from the outer circumferential surface of the transfer roller 42 to the surface of the electrode current collector 31 transported by the support roller 43 by gradually increasing the rotation speed of each of the supply roller 41, the transfer roller 42, and the support roller 43 in this order.

[0102] Although not particularly limited, the size (width) of the gap between the supply roller 41, the transfer roller 42, and the support roller 43 can be set to a size such that the average film thickness of the electrode active material layer 32 formed is 10 μm to 300 μm (for example, 20 μm to 150 μm).

[0103] The size of the supply roller 41, the transfer roller 42, and the support roller 43 is not particularly limited, and can be the same as in the conventional roller film forming device, for example, the diameter can be 50 mm to 500 mm. The diameters of the supply roller 41, the transfer roller 42, and the support roller 43 can be the same or different. In addition, the width of the electrode active material layer 32 can be the same as in the conventional roller film forming device, and can be appropriately determined according to the width of the electrode current collector 31 to which the electrode active material layer 32 is to be formed. In addition, the material of the outer circumferential surface of the supply roller 41, the transfer roller 42, and the support roller 43 can be the same as the material of the rotating roller in the conventional publicly known roller film forming device, for example, SUS steel, SUJ steel, and the like.

[0104] It should be noted that Figure 3 In the above embodiment, the supply roller 41, the transfer roller 42, and the support roller 43 are arranged with the rotation axes of each of the rollers arranged horizontally, but the arrangement of the rollers is not limited to this.

[0105] In the electrode forming step S120 disclosed herein, first, the wetted powder 20 is supplied between the pair of supply rollers 41 and the transfer roller 42 rotating in opposite directions. The wetted powder 20 is transported to the gap of the pair of rollers by the supply rollers 41 and the transfer roller 42 rotating in opposite directions. Next, the wetted powder 20 is formed into a film shape while being compressed by the gap of the supply rollers 41 and the transfer roller 42 to form the electrode active material layer 32. That is, the wetted powder 20 is compressed by the supply rollers 41 and the transfer roller 42, and the wetted powder 20 is integrated with each other, stretched, and formed into the film-shaped electrode active material layer 32. At this time, the wetted powder 20 (specifically, the aggregated particles) is not particularly limited, but it is presumed that the wetted powder 20 is bonded by the liquid cross-linking force. As the inter-particle adhesive force (bonding force), in addition to the liquid cross-linking force, the van der Waals force, the electrostatic force, and the like can be cited, but the liquid cross-linking force can exert a greater adhesive force, and for example, when the solid content rate is 70% by mass or more (for example, 70 to 87% by mass), an appropriate adhesive force is exerted. In addition to this, by using a non-aqueous electrolyte solution having a high viscosity, the bonding force is strengthened. Therefore, by compressing the wetted powder 20 in the capillary state described above, even if the binder resin is not substantially contained, the film-shaped electrode active material layer 32 can be formed.

[0106] Next, the electrode active material layer 32 is transported while being attached to the transfer roller 42. As described above, the rotational speed of the transfer roller 42 is set to be faster than that of the supply rollers 41, and thus the formed electrode active material layer 32 is attached to the transfer roller 42. The electrode active material layer 32 attached to the transfer roller 42 is transported by the rotation of the transfer roller 42 and is transferred to the electrode current collector 31 supplied by the support roller 43. At this time, the electrode active material layer 32 is brought into contact with the electrode current collector 31 with a certain degree of pressure, and thus the electrode active material layer 32 is transferred to the electrode current collector 31. Thus, an electrode having the electrode active material layer 32 on the electrode current collector 31 can be obtained.

[0107] The electrode active material layer composed of the general slurry-like electrode material is formed by preparing an electrode active material and a binder into a slurry-like electrode material with a proper solvent, coating the obtained electrode material on a current collector, and drying and pressing it. According to this method, when the slurry-like electrode material coated on the current collector is dried, a phenomenon of segregation of the binder with a small specific gravity to the surface side, i.e., migration, occurs. If this migration occurs, the adhesion of the electrode current collector to the electrode active material layer can be reduced. Also, in the manufacturing process of the nonaqueous electrolyte secondary battery, or at the time of use of the nonaqueous electrolyte secondary battery, the electrode active material layer is easily peeled from the electrode current collector at the time of repeated charge and discharge. In addition, the slurry-like electrode material has a problem of reduction in productivity because of a low solid content rate (typically, 55% or less) and a time-consuming removal of the solvent based on drying or the like. In contrast, in the electrode manufacturing method disclosed herein, since a nonaqueous electrolyte is used as a liquid component, there is no need to remove the liquid component. Thus, a high-quality electrode in which the electrode active material layer is not peeled from the electrode current collector can be manufactured without migration. In addition, according to the above reasons, there is no need for a solvent removal process and a solvent recovery device, and an improvement in productivity is also achieved. In addition to this, since a wet powder substantially containing no binder resin that can be a resistance component is used and is formed into a film while being compressed by the above roll film forming device, the electrode density can be sufficiently improved. Thus, there is no need for the pressing process (process of adjusting the density of the electrode active material layer) in the conventional manufacturing method. Therefore, according to the electrode manufacturing method disclosed herein, a high-quality electrode higher than the conventional one can be efficiently manufactured.

[0108] <electrode body housing process>

[0109] In the electrode body housing process S130, an electrode body is produced using the above-described manufactured sheet-shaped electrode, and the electrode body is housed in a battery case. As the production method of the electrode body, specifically, the electrode body is produced by stacking the sheet-shaped positive electrode and the sheet-shaped negative electrode via the sheet-shaped separator.

[0110] As the separator, for example, a porous sheet (film) composed of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, polyamide, or the like can be given. The porous sheet can be a single layer structure, or a laminated structure of two or more layers (for example, a three-layer structure in which a PP layer is laminated on both surfaces of a PE layer). The separator can be provided with a heat-resistant layer (HRL).

[0111] The sheet-shaped electrode can be used as it is, or can be used after being cut into a rectangular flat plate shape. For example, a wound electrode body can be produced by winding in the longitudinal direction in a state in which the sheet-shaped positive electrode and the negative electrode are stacked via the separator. In addition, for example, a stacked electrode body can be produced by stacking the positive electrode and the negative electrode cut into a rectangular flat plate shape via the separator.

[0112] The electrode body is housed in a battery case. The battery case can be a box-shaped battery case made of a metal material that is high in strength, light in weight, and good in thermal conductivity, and typically can be a laminate case made of a laminate film having a multilayer structure.

[0113] <Non-aqueous solvent injection step>

[0114] In the non-aqueous solvent injection step S140, a prescribed non-aqueous solvent is injected into the battery case in which the electrode body is housed. The non-aqueous solvent injected here typically can be the non-aqueous solvent contained in the non-aqueous electrolyte solution used in the granulation step S110. In the manufacturing method disclosed herein, a step of removing the liquid component is not required to be performed, and therefore, the liquid component (non-aqueous electrolyte solution) added in the granulation step S110 remains substantially in the electrode body. Therefore, the non-aqueous solvent injected in the non-aqueous solvent injection step S140 can be mixed with the non-aqueous electrolyte solution remaining in the electrode body.

[0115] The non-aqueous electrolyte solution injected in the conventional manufacturing method typically contains a non-aqueous solvent and a supporting salt. The non-aqueous electrolyte solution used in the granulation step S110 disclosed herein is high in viscosity as described above, and therefore, it is preferable that the concentration of the supporting salt in the non-aqueous electrolyte solution be set to be high. For example, by previously adding the supporting salt to the non-aqueous electrolyte solution used in the granulation step S110 in such a manner that the concentration of the supporting salt in the non-aqueous electrolyte solution when the secondary battery is constructed becomes approximately 1 mol / L or so, it is possible to inject only the non-aqueous solvent in this non-aqueous solvent injection step S140. The non-aqueous solvent can be injected in such a manner that the concentration of the supporting salt in the non-aqueous electrolyte solution when the secondary battery is constructed becomes, for example, 0.7 mol / L to 1.3 mol / L.

[0116] The supporting salt is a necessary component, since it is used as a main electrolyte and enables a balance between the total ion content in the non-aqueous electrolyte solution and the viscosity of the electrolyte solution to be moderate. On the other hand, from the viewpoint of extending the storage period of the non-aqueous electrolyte solution, it is preferable to prepare it in a state in which the non-aqueous solvent and the supporting salt are not mixed. In addition, by not containing the supporting salt at the stage of injection, it is possible to inject a liquid (non-aqueous solvent) in a state that is lower in viscosity than the conventional non-aqueous electrolyte solution, and therefore, it is possible to shorten the injection time. In addition to this, since the electrode is impregnated with sufficient non-aqueous electrolyte solution, it is not necessary to wait for the non-aqueous solvent to impregnate the electrode body, and therefore, it is possible to shorten the time of the non-aqueous solvent injection step S140. Therefore, according to the manufacturing method disclosed herein, it is possible to manufacture a non-aqueous electrolyte secondary battery by a manufacturing method that does not contain a solvent that adversely affects the performance of the battery and that reduces the production cost.

[0117] <Lithium ion secondary battery>

[0118] Hereinafter, a lithium-ion secondary battery 100 that can be constructed by the manufacturing method of the battery disclosed herein will be described. Figure 4 is an explanatory diagram schematically showing one example of the lithium-ion secondary battery 100.

[0119] Figure 4 The lithium-ion secondary battery 100 shown is constructed by housing a flat-shaped wound electrode body 80 and a non-aqueous electrolyte solution (not shown) in a box-shaped battery case 50 that can be sealed. In the battery case 50, a positive electrode terminal 52 and a negative electrode terminal 54 for external connection, and a thin-walled safety valve 56 that is set in such a manner that the internal pressure of the battery case 50 is released when the internal pressure rises to a prescribed level or more are provided. In addition, an injection port (not shown) for injecting a non-aqueous electrolyte solution or a non-aqueous solvent is provided in the battery case 50. The positive electrode terminal 52 is electrically connected to a positive electrode current collector 52a. The negative electrode terminal 54 is electrically connected to a negative electrode current collector 54a.

[0120] The wound electrode body 80 typically has a configuration in which a long strip-shaped positive electrode (hereinafter, referred to as a positive electrode strip 60) and a long strip-shaped negative electrode (hereinafter, referred to as a negative electrode strip 70) are overlapped via a long strip-shaped separator 90 and wound in the longitudinal direction. The positive electrode strip 60 has a configuration in which a positive electrode active material layer 64 is formed on one face or both faces of a positive electrode current collector 62 in the longitudinal direction. The negative electrode strip 70 has a configuration in which a negative electrode active material layer 74 is formed on one face or both faces of a negative electrode current collector 72 in the longitudinal direction. On the edge portion of the positive electrode current collector 62 on the width direction side, a region in which the positive electrode current collector 62 is exposed without the positive electrode active material layer 64 being formed along the edge portion (i.e., a positive electrode active material layer non-formed portion 66) is provided. On the edge portion of the negative electrode current collector 72 on the other width direction side, a region in which the negative electrode current collector 72 is exposed without the negative electrode active material layer 74 being formed along the edge portion (i.e., a negative electrode active material layer non-formed portion 76) is provided. The positive electrode current collector 52a and the negative electrode current collector 54a are respectively joined to the positive electrode active material layer non-formed portion 66 and the negative electrode active material layer non-formed portion 76.

[0121] The positive electrode (positive electrode strip 60) and the negative electrode (negative electrode strip 70) can use the positive electrode and the negative electrode obtained by the manufacturing method described above. Note that in the present configuration example, the positive electrode and the negative electrode have the electrode active material layer 32 (positive electrode active material layer 64 and negative electrode active material layer 74) formed on both faces of the electrode current collector 31 (positive electrode current collector 62 and negative electrode current collector 72).

[0122] The lithium-ion secondary battery 100 constructed as described above can be used for various applications. Suitable applications include driving power supplies for vehicles such as battery-electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The lithium-ion secondary battery 100 can also be used in the form of a battery pack comprising multiple batteries connected in series and / or in parallel.

[0123] Hereinafter, examples related to the electrodes disclosed herein will be described, but the technology disclosed herein is not intended to be limited to the contents shown in these examples.

[0124] <Example 1>

[0125] Use the following positive electrode materials, Figure 1 The process shown is used to manufacture a non-aqueous electrolyte secondary battery.

[0126] First, as a positive electrode active material, an average particle size (D 50 ) is 20μm lithium transition metal oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) and acetylene black as a conductive material. A non-aqueous electrolyte solution was prepared by dissolving LiPF6 as a supporting salt at a concentration of 4.1 mol / L in a mixed solvent containing tetraethylene glycol dimethyl ether (G4), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) at a volume ratio of 30:40:30. The viscosity of this non-aqueous electrolyte solution at 25°C was measured to be 122 mPa·s.

[0127] 90 parts by mass of the above-mentioned positive electrode active material and 10 parts by mass of acetylene black were placed in a planetary mixer and mixed to obtain a mixture of powder materials composed of the above-mentioned solid materials. A non-aqueous electrolyte was added to the obtained mixture so that the solid content became 70% by mass, and the mixture was further mixed. The wet mixture was granulated using a roller mill to produce a wet powder (positive electrode material) of this example.

[0128] Next, the resulting wet powder (positive electrode material) is fed to the aforementioned roll film forming apparatus to form a positive electrode active material layer on the surface of a separately prepared long sheet of positive electrode current collector made of aluminum foil. This yields a positive electrode sheet having a positive electrode active material layer formed on the sheet of positive electrode current collector.

[0129] Next, as a negative electrode, a negative electrode active material having an average particle size (D 50) graphite powder having a particle diameter of 10 μm. As the nonaqueous electrolyte, the nonaqueous electrolyte used in the above-described positive electrode was prepared. The nonaqueous electrolyte was added to the graphite powder in such a manner that the solid content rate became 70 mass% and mixed. The mixture in the wet state was granulated using a roll mill to produce a wet powder (negative electrode material).

[0130] The obtained wet powder (negative electrode material) was supplied to the film forming device to form a negative electrode active material layer on the surface of a long sheet-shaped negative electrode current collector prepared separately from a copper foil. Thus, a negative electrode sheet having a negative electrode active material layer formed on a sheet-shaped negative electrode current collector was obtained.

[0131] In addition, as separators, two porous polyolefin sheets having a three-layer structure of PP / PE / PP were prepared.

[0132] The produced positive electrode sheet, negative electrode sheet, and the two prepared separators were overlapped and wound to produce a wound electrode body. Electrode terminals were attached to the positive electrode sheet and negative electrode sheet of the produced wound electrode body by welding, and the wound electrode body was housed in a battery case having an injection port.

[0133] A nonaqueous solvent was injected from the injection port, and the injection port was hermetically sealed with a sealing cap. Note that, as the nonaqueous solvent, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) at a volume ratio of 30:40:30 was prepared, and the mixed solvent was injected in such a manner that the concentration of the supporting salt in the nonaqueous electrolyte of the constructed secondary battery became 1.0 mol / L. By the above operation, a lithium ion secondary battery for evaluation was obtained.

[0134] <Comparative Example 1>

[0135] As a comparative example, an electrode was produced using a nonaqueous electrolyte having a viscosity equivalent to that of the conventional nonaqueous electrolyte.

[0136] First, the same positive electrode active material and conductive material as in the above-described Example 1 were prepared. As the nonaqueous electrolyte, a nonaqueous electrolyte in which LiPF6 was dissolved as a supporting salt at a concentration of 1 mol / L in a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (EMC) at a volume ratio of 30:40:30 was prepared. The viscosity of the nonaqueous electrolyte at 25°C was measured, and the result was 3.1 mPa-s.

[0137] Ninety mass parts of the above-described positive electrode active material and 10 mass parts of acetylene black were put into a planetary mixer and mixed to obtain a mixture of powder materials composed of the above-described solid materials. A nonaqueous electrolyte was added to the obtained mixture in such a manner that the solid content rate became 70 mass%, and further stirred. The mixture in the wet state was granulated using a roll mill. Thus, a wet powder (positive electrode material) was produced.

[0138] Next, the obtained wet powder (positive electrode material) is supplied to the above-mentioned roll film forming device, and a positive electrode active material layer is formed on the surface of a long sheet-shaped positive electrode current collector prepared separately from an aluminum foil. Thus, a positive electrode sheet having the positive electrode active material layer formed on the sheet-shaped positive electrode current collector is obtained.

[0139] Next, as the negative electrode, graphite powder having an average particle diameter (D50) of 10 μm based on a laser diffraction-scattering method as a negative electrode active material is prepared. As the nonaqueous electrolyte, the same nonaqueous electrolyte as the positive electrode of the above-mentioned Comparative Example 1 is prepared. The nonaqueous electrolyte is added to the graphite powder so that the solid content rate becomes 70 mass%, and mixed. The mixture in the wet state is granulated using a roll mill, and a wet powder (negative electrode material) is obtained. 50

[0140] Next, the obtained wet powder (negative electrode material) is supplied to the above-mentioned film forming device, and a negative electrode active material layer is formed on the surface of a long sheet-shaped negative electrode current collector prepared separately from a copper foil. Thus, a negative electrode sheet having the negative electrode active material layer formed on the sheet-shaped negative electrode current collector is obtained.

[0141] In addition, as the separator sheets, two porous polyolefin sheets having a three-layer structure of PP / PE / PP are prepared.

[0142] The prepared positive electrode sheet, negative electrode sheet, and the prepared two separator sheets are overlapped, and wound to produce a wound electrode body. Electrode terminals are attached to the positive electrode sheet and the negative electrode sheet of the prepared wound electrode body by welding, and housed in a battery case having a pouring inlet.

[0143] A nonaqueous electrolyte is poured from the above-mentioned pouring inlet, and the pouring inlet is hermetically sealed with a sealing cap. It should be noted that, as the nonaqueous electrolyte, a nonaqueous electrolyte in which LiPF6 as a supporting salt is dissolved at a concentration of 1 mol / L in a mixed solvent containing EC:DMC:EMC = 30:40:30 by volume is prepared. By the above operation, a lithium ion secondary battery for evaluation is obtained.

[0144] <Activation Treatment>

[0145] An activation treatment (initial charge) is performed on each of the lithium ion secondary batteries for evaluation in an environment at 25°C. The activation treatment is a constant current-constant voltage method, and after constant current charging to 4.2 V is performed at a current value of 1 / 3 C, constant voltage charging is performed until the current value becomes 1 / 50 C, whereby a full charge state is formed. Then, constant current discharging is performed at a current value of 1 / 3 C until the voltage becomes 3.0 V.

[0146] <Initial Resistance Measurement>

[0147] ​After adjusting each of the lithium-ion secondary batteries after the activation treatment to a SOC (State of charge) of 27%, the batteries were placed in a temperature environment of -30°C. Discharge was performed at a current value of 12C for 10 seconds, and the voltage drop (ΔV) was determined. The battery resistance was calculated by dividing the voltage drop ΔV by the discharge current value (12C), and was used as the initial resistance.

[0148] When the initial resistance of Comparative Example 1 was set to 1, the initial resistance of Example 1 was 0.95. Therefore, the wet powder disclosed herein substantially does not contain a binder resin that can be a resistance component and a solvent that is concerned to adversely affect the battery performance, and the viscosity of the nonaqueous electrolyte is high, and thus, the initial resistance of the secondary battery having an electrode composed of the wet powder can be reduced. That is, the wet powder composed of agglomerated particles including an electrode active material and a nonaqueous electrolyte, having a solid content rate of 70 mass% or more when the entire wet powder is set to 100 mass%, and including a nonaqueous electrolyte having a viscosity of 25 mPa-S or more at 25°C can suppress the reduction in the battery performance and increase the electrode density.

[0149] The above detailed description of the specific examples of the present application, but they are merely illustrative and do not limit the scope of the claimed. In the claimed range of technology includes the technology of the above examples of the specific examples of various modifications, changes.

Claims

1. A wet powder for forming an electrode active material layer on an electrode collector of either a positive electrode or a negative electrode, The wet powder is composed of aggregated particles containing electrode active material and non-aqueous electrolyte. The wet powder is in powder form, When the entire wet powder is taken as 100% by mass, the solid content is 70% by mass or more. In the agglomerated particles, the solid phase and the liquid phase form a capillary state. The non-aqueous electrolyte contains a non-aqueous solvent and a supporting salt, The viscosity of the non-aqueous electrolyte at 25° C. is 25 mPa·S to 130 mPa·S.

2. The wet powder according to claim 1, wherein The non-aqueous solvent comprises at least one selected from ethers, carbonates, glymes, esters, carbamates, amides, sulfides, sulfoxides, sulfones and ketones, The viscosity of the non-aqueous solvent at 25° C. is 0.6 mPa·S to 4.1 mPa·S.

3. The wet powder according to claim 2, wherein: The non-aqueous solvent contains at least the carbonates and the glymes, and contains 30 vol % or more of the glymes when the non-aqueous solvent is taken as 100 vol %.

4. The wet powder according to any one of claims 1 to 3, wherein The concentration of the supporting salt in the non-aqueous electrolyte is 2 mol / L to 5 mol / L.

5. A method for manufacturing a non-aqueous electrolyte secondary battery, characterized in that: A method for manufacturing a non-aqueous electrolyte secondary battery having an electrode body having a positive electrode and a negative electrode and a non-aqueous electrolyte containing a non-aqueous solvent and a supporting salt, comprising the following steps: a step of granulating a wet powder composed of aggregated particles containing at least an electrode active material and the non-aqueous electrolyte; a step of supplying an electrode active material layer composed of the wet powder onto an electrode current collector to form an electrode, a step of housing an electrode assembly manufactured using the electrode in a battery case, and a step of injecting the non-aqueous solvent into a battery case containing the electrode assembly; The granulation process comprises: mixing the electrode active material and the non-aqueous electrolyte, and Compressing and granulating the mixture of the electrode active material and the non-aqueous electrolyte; The viscosity of the non-aqueous electrolyte solution at 25° C. in the granulation step is adjusted to 25 mPa·S to 130 mPa·S.

6. The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 5, wherein: The concentration of the supporting salt in the non-aqueous electrolyte in the granulation step is 2 mol / L to 5 mol / L.

7. The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 5 or 6, wherein: The electrode forming process forms the electrode by allowing the wet powder supplied between the first roller and the second roller to adhere to the outer peripheral surface of the second roller as the electrode active material layer, and transferring the electrode active material layer from the outer peripheral surface of the second roller to the surface of the electrode collector supplied separately to the second roller, wherein the second roller is arranged opposite to the first roller.

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