Method for producing nonaqueous electrolyte secondary battery

Abstract

To provide a manufacturing method of a nonaqueous electrolyte secondary battery capable of improving productivity.SOLUTION: A method of manufacturing a nonaqueous electrolyte secondary battery includes obtaining an electrode assembly by stacking an electrode plate and a separator with an inclusion interposed therebetween, accommodating the electrode assembly in an outer package, and injecting a first solution into the outer package accommodating the electrode assembly. The inclusion is a component constituting the nonaqueous electrolyte solution and contains a compound having a melting point of 15 to 45 °C. The first solution contains at least a part of remaining components excluding components contained in the non-aqueous electrolyte solution in the inclusion from components contained in the non-aqueous electrolyte solution. A ratio (C1 / C0) of a content C1 [parts by mass] of the compound in the inclusion to a content C0 [parts by mass] of the compound in the nonaqueous electrolytic solution is 100 / 100 to 8 / 100.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery. [Background technology]

[0002] It is known that in secondary batteries such as lithium ion batteries, an electrode assembly in which an electrode plate and a separator are bonded together is used (for example, Patent Documents 1 and 2). Patent Document 2 discloses that an adhesive solution containing a component used in a non-aqueous electrolyte is used to bond the electrode plate and the separator together. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-54503 [Patent Document 2] Japanese Patent Application Publication No. 2019-117700 Summary of the Invention [Problem to be solved by the invention]

[0004] Secondary batteries are typically manufactured through a liquid injection process in which a nonaqueous electrolyte is injected into an exterior housing housing an electrode assembly. Some of the components constituting the nonaqueous electrolyte have low melting points. Nonaqueous electrolytes containing components with low melting points tend to have high viscosity. Highly viscous nonaqueous electrolytes injected in the liquid injection process have difficulty permeating the electrode assembly, which increases the time required for the nonaqueous electrolyte to permeate the entire electrode assembly, resulting in reduced productivity of secondary batteries.

[0005] An object of the present disclosure is to provide a method for producing a non-aqueous electrolyte secondary battery that can improve productivity. [Means for solving the problem]

[0006] [1] A method for manufacturing a non-aqueous electrolyte secondary battery including an electrode assembly in which electrode plates and a separator are stacked, a non-aqueous electrolyte solution, and an exterior body that accommodates the electrode assembly and the non-aqueous electrolyte solution, obtaining the electrode assembly by stacking the electrode plates and the separators with an intervening material therebetween; The electrode assembly is housed in the outer casing; and injecting a first liquid into the exterior housing that houses the electrode assembly; the inclusions are components constituting the nonaqueous electrolyte solution and contain a compound having a melting point of 15 to 45°C, the first liquid contains at least a portion of the remaining components obtained by excluding the components contained in the nonaqueous electrolyte solution in the inclusions from the components contained in the nonaqueous electrolyte solution, a ratio (C1 / C0) of a content C1 [parts by mass] of the compound in the inclusions to a content C0 [parts by mass] of the compound in the nonaqueous electrolyte solution is 100 / 100 to 8 / 100. [2] Obtaining the electrode body includes: Applying a second liquid containing the inclusions to at least one of the electrode plate and the separator; and The method for producing a nonaqueous electrolyte secondary battery according to [1], further comprising: interposing the applied second liquid between the electrode plate and the separator. [3] The method for producing a nonaqueous electrolyte secondary battery according to [2], further comprising cooling the applied second liquid to reduce the fluidity of the second liquid. [4] The method for producing a nonaqueous electrolyte secondary battery according to [2], further comprising cooling the applied second liquid to within ±5°C of the melting point of the compound. [5] The method for producing a nonaqueous electrolyte secondary battery according to [3] or [4], further comprising bringing the separator coated with the second liquid into contact with a cooling roller. [6] The separator is a long separator, The method for producing a nonaqueous electrolyte secondary battery according to any one of [2] to [5], further comprising applying the second liquid to the separator while it is being transported. [7] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [6], wherein the inclusions are present in the center of the surface where the electrode plate and the separator face each other, and are not present in at least a part of the edge portions. [8] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [7], wherein the inclusions are present on the entire surface where the electrode plate and the separator face each other. [9] The method for producing a non-aqueous electrolyte secondary battery according to any one of [1] to [8], wherein the inclusions contain ethylene carbonate.

[10] The method for producing a non-aqueous electrolyte secondary battery according to any one of [1] to [9], wherein the first liquid contains a part of the solvent contained in the non-aqueous electrolyte solution.

[11] The method for producing a non-aqueous electrolyte secondary battery according to any one of [1] to

[10] , wherein the content of the compound in the non-aqueous electrolyte solution is 1 to 7 mass %. [Effects of the Invention]

[0007] According to the present disclosure, non-aqueous electrolyte secondary batteries can be manufactured with improved productivity. [Brief explanation of the drawings]

[0008] [Figure 1] 2 is a flowchart illustrating a manufacturing process of a nonaqueous electrolyte secondary battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification, unless otherwise specified, a numerical range such as "m to n" includes both the upper and lower limits. That is, "m to n" represents a numerical range of "m or more and n or less." A numerical value arbitrarily selected from within the numerical range may be set as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, or in a figure.

[0010] (Method of manufacturing non-aqueous electrolyte secondary battery) 1 is a flowchart illustrating the manufacturing process of a nonaqueous electrolyte secondary battery according to an embodiment. The manufacturing method (hereinafter also referred to as "the present method") of a nonaqueous electrolyte secondary battery (hereinafter also referred to as "secondary battery") according to this embodiment is, for example, a manufacturing method of a lithium ion secondary battery that performs charging and discharging by absorbing and releasing lithium ions. Hereinafter, a secondary battery manufactured by this method will also be referred to as "the present battery." The present battery includes an electrode assembly in which electrode plates and separators are stacked, a nonaqueous electrolyte solution, and an exterior housing that accommodates the electrode assembly and the nonaqueous electrolyte solution.

[0011] This method includes stacking electrode plates and separators with an intervening material therebetween to obtain an electrode assembly (hereinafter also referred to as the "stacking step"); Housing the electrode assembly in the outer casing (hereinafter also referred to as the "housing step"); and Injecting the first liquid into the exterior housing that houses the electrode assembly (hereinafter also referred to as the "liquid injection step").

[0012] The inclusions are components of the non-aqueous electrolyte and contain a compound (hereinafter also referred to as "first compound") having a melting point of 15 to 45°C. The first liquid contains at least a portion of the components (hereinafter also referred to as "residual components") remaining after excluding the components contained in the non-aqueous electrolyte in the inclusions from the components contained in the non-aqueous electrolyte. In this method, the ratio (C1 / C0) of the content C1 [parts by mass] of the first compound in the inclusions to the content C0 [parts by mass] of the first compound in the non-aqueous electrolyte is 100 / 100 to 8 / 100.

[0013] Because the melting point of the first compound is within the above range, the viscosity of the nonaqueous electrolyte containing the first compound is likely to be high. The content of the first compound in the first liquid is adjusted to be greater than the content of the first compound in the inclusions and less than the content C0 of the first compound in the nonaqueous electrolyte by mixing with the first compound in the inclusions, so that the content is less than the content C0 of the first compound in the nonaqueous electrolyte. Therefore, the first liquid has a lower viscosity than the nonaqueous electrolyte. Because a nonaqueous electrolyte with a high viscosity has difficulty permeating the electrode assembly, when the nonaqueous electrolyte is injected into an exterior housing containing the electrode assembly, it takes a long time for the nonaqueous electrolyte to uniformly permeate the electrode assembly. In contrast, the present method injects a first liquid with a lower viscosity than the nonaqueous electrolyte, thereby shortening the time required for the first liquid to uniformly permeate the electrode assembly and improving the productivity of the battery.

[0014] In this method, at least a portion of the first compound is preliminarily present in the electrode assembly as an inclusion between the electrode plate and the separator. After the electrode assembly containing the first compound is housed in an outer casing, a first liquid is injected into the outer casing, whereby the first compound in the inclusion mixes with the first liquid to form a nonaqueous electrolyte. Therefore, this method allows the battery to be produced with high productivity without changing the content of the first compound in the nonaqueous electrolyte of the battery.

[0015] Inclusions containing the first compound tend to have high viscosity and low fluidity. Because such inclusions are easily interposed between the electrode plate and the separator, they tend to adhere to each other when stacked. This prevents misalignment between the electrode plate and the separator, allowing the electrode assembly to be housed in an outer casing while maintaining the shape of the electrode assembly obtained in the stacking process. This method eliminates the need for a pressing process to press the electrode plate and separator laminate, which is typically performed to adhere the electrode plate and separator together during the production of the electrode assembly.

[0016] Each step of this method will now be described in detail. (Obtaining the electrode body (lamination process)) In the lamination step, an electrode assembly is obtained. The electrode assembly may include an electrode plate and a separator. The electrode plate is at least one of a positive electrode plate and a negative electrode plate, and may be both a positive electrode plate and a negative electrode plate. In the lamination step, the electrode plate and the separator are laminated with an inclusion containing the first compound interposed therebetween. The temperature condition for carrying out the lamination step may be, for example, (melting point of the first compound + 5°C) or less, (melting point of the first compound + 3°C) or less, (melting point of the first compound - 3°C) or less, or (melting point of the first compound - 5°C) or less.

[0017] The inclusions need only contain at least the first compound, and may contain only the first compound. The first compound is a component constituting the non-aqueous electrolyte. The first compound is preferably at least one of a component contained as a solvent in the non-aqueous electrolyte and a component contained as an additive in the non-aqueous electrolyte, and more preferably a component contained as a solvent in the non-aqueous electrolyte. When the first compound is a solvent contained in the non-aqueous electrolyte, the solvent is preferably a non-aqueous solvent, and more preferably an organic solvent. The first compound contained in the inclusions may be one type or a combination of two or more types.

[0018] The melting point of the first compound may be 15 to 45°C, 18 to 45°C, 20 to 45°C, 25 to 43°C, or 30 to 40°C. The melting point can be determined by differential scanning calorimetry (DSC) measurement under 1 atm. When the inclusions contain two or more first compounds, the melting points of the two or more first compounds may be the same or different. When the melting point of the first compound is within the above range, the productivity of the battery can be easily improved by this method. When the melting point of the first compound is outside the above range, the temperature difference with room temperature becomes large, making temperature control difficult and requiring a long time to change the temperature to the set temperature, making it difficult to improve productivity.

[0019] The ratio (C1 / C0) of the contents C1 [parts by mass] of the first compound in the inclusions and the non-aqueous electrolyte to C0 [parts by mass] of the first compound in each of the inclusions and the non-aqueous electrolyte may be 100 / 100 to 8 / 100, preferably 100 / 100 to 10 / 100, and may be 99 / 100 to 15 / 100, 95 / 100 to 20 / 100, or 90 / 100 to 30 / 100. If the ratio (C1 / C0) is below the above range, it is difficult to expect improvement in the productivity of the present battery. When the inclusions and the non-aqueous electrolyte contain two or more types of first compounds, the contents C1 and C0 refer to the total amounts of the first compounds contained in the inclusions and the non-aqueous electrolyte, respectively.

[0020] The first compound is not particularly limited as long as it is a component of the non-aqueous electrolyte and has a melting point within the above range. Examples of the first compound include carbonates such as ethylene carbonate (EC), vinylene carbonate (VC), and fluoroethylene carbonate (FEC); nitrogen-containing compounds such as 3-methyloxazolidinone (MOX); esters such as γ-butyrolactone (BL); sulfur-containing compounds such as dimethyl sulfoxide (DMSO), sulfolane (S), and 1,3-propane sultone. The first compound is preferably one or more of EC, VC, and FEC, and more preferably EC.

[0021] The inclusions may contain a second compound other than the first compound. The second compound may be a component constituting the non-aqueous electrolyte, a compound having a melting point outside the melting point range of the first compound, or a component not constituting the non-aqueous electrolyte. The inclusions preferably contain only components constituting the non-aqueous electrolyte. Therefore, the second compound is preferably a component constituting the non-aqueous electrolyte, and may be, for example, a solvent and additive other than the first compound, as well as an electrolyte.

[0022] The electrolyte, such as lithium salt, contained in the non-aqueous electrolyte may increase the viscosity of the non-aqueous electrolyte. Therefore, the viscosity of the first liquid may be reduced by incorporating a lithium salt into the inclusions and reducing the content of the lithium salt in the first liquid injected in the liquid injection step. When the inclusions contain a lithium salt, it is preferable to perform the lamination step under an atmosphere of an inert gas, such as nitrogen gas, He gas, or Ar gas, in order to prevent the lithium salt from reacting with oxygen or moisture in the air.

[0023] The inclusions may be present at least partially between the electrode plates and the separator of the electrode assembly, and may be present in part or all of the space between the electrode plates and the separator. By stacking the electrode plates and the separator with the inclusions interposed therebetween, it is possible to eliminate the need for a press process to apply pressure to the electrode plates and the separator to bring them into close contact with each other.

[0024] The inclusions may be present on the entire surface where the electrode plate and the separator face each other (hereinafter also referred to as the "facing surface"). By having the inclusions on the entire surface of the facing surface, the electrode plate and the separator can be closely attached to each other over the entire facing surface. From the viewpoint of suppressing variations in the thickness of the electrode body and making it easier to accommodate the electrode body in an exterior body in the accommodation step, it is preferable that the inclusions present on the entire facing surface be formed to a constant thickness over the entire facing surface.

[0025] From the viewpoint of closely adhering the electrode plate and the separator, the inclusions may be present partially, and the proportion of the area where the inclusions are present may be 3% or more, 5% or more, or 10% or more of the total area of ​​the opposing surfaces of the electrode plate.

[0026] The inclusions may be present, for example, in the central portion of the opposing surfaces, but may not be present in at least a portion of the edges of the opposing surfaces. The central portion of the opposing surfaces refers to a region other than the edges, and may be a region including the center of the opposing surfaces. The edges free of inclusions may be all edges of the opposing surfaces, or may be only some edges of the opposing surfaces. A nonaqueous electrolyte solution containing the first compound is less likely to penetrate into the electrode body. On the other hand, by having the inclusions present in the central portion of the opposing surfaces in the lamination process, the first compound can be more easily uniformly distributed inside the electrode body in a short time by the injection process, thereby improving the productivity of the battery.

[0027] When inclusions are present between the electrode plates and the separator, it may be difficult to remove the solvent used to form the active material layers (positive electrode active material and negative electrode active material layers) contained in the electrode plates even after drying the electrode assembly. Therefore, a drying treatment to remove the solvent from the electrode plates may be performed before stacking the electrode plates and the separator. When inclusions are present on the entire opposing surfaces, it is preferable to dry the electrode plates before stacking the electrode plates and the separator.

[0028] The method for interposing the intervening material between the electrode plate and the separator is not particularly limited, and examples thereof include a method of applying a second liquid containing the intervening material to at least one of the electrode plate and the separator and interposing the applied second liquid between the electrode plate and the separator; and a method of sandwiching a molded body in which the intervening material is formed into a sheet or the like between the electrode plate and the separator.

[0029] The second liquid contains at least the first compound because it contains inclusions. The second liquid may be, for example, the first compound in a liquid state, or a liquid containing the first compound. When the second liquid is the first compound, the first compound may be brought into a liquid state by heating or the like. The liquid containing the first compound is, for example, a liquid in which the first compound is dissolved or dispersed in a liquid component other than the first compound.

[0030] The second liquid may be applied to the electrode plate, the separator, or both the electrode plate and the separator. In the lamination step, the electrode plate and the separator are laminated with the second liquid applied to at least one of the electrode plate and the separator interposed therebetween. The method for applying the second liquid is not particularly limited, and examples thereof include spraying, gravure printing, flexographic printing, offset printing, die coating, blade coating, dip coating, inkjet printing, and spin coating.

[0031] The second liquid may be applied to the separator as it is being conveyed. In this case, roller application is preferred, which can apply the second liquid in contact with the separator. Roller application allows the second liquid to be applied effectively to separators being conveyed at high speed. The separator may be a long separator.

[0032] In the lamination step, the second liquid applied to the electrode plates and / or separators may be cooled. The cooling of the second liquid may be carried out after application to the electrode plates and / or separators, and before or after laminating the electrode plates and separators with the second liquid interposed therebetween.

[0033] The cooling temperature of the second liquid may be any temperature at which the fluidity of the second liquid decreases. The decrease in the fluidity of the second liquid can be confirmed by the viscosity of the second liquid, and an increase in the viscosity of the second liquid indicates a decrease in the fluidity of the second liquid. By cooling the second liquid so as to decrease the fluidity of the second liquid, the second liquid can be retained on the electrode plates and / or separators to which the second liquid is applied. Stacking the electrode plates and separators in this state makes it easier to bring the electrode plates and separators into close contact with each other.

[0034] The cooling temperature of the second liquid may be, for example, within a range of ±5° C. of the melting point of the first compound, a temperature within a range of ±4° C., or a temperature within a range of ±3° C. Cooling the second liquid to within this temperature range makes it easier to reduce the fluidity of the second liquid.

[0035] The method for cooling the second liquid is not particularly limited, and examples thereof include a method of bringing the electrode plates and / or separators coated with the second liquid into contact with a cooling roller; a method of exposing the second liquid coated on the electrode plates and / or separators to cold air or the like; and a method of transporting the electrode plates and / or separators coated with the second liquid into a cooled space. The cooling rollers may be support rollers that support the separators, or transport rollers that transport the separators. When the separators used in the electrode assembly are long separators, the second liquid may be applied to the separators while they are being transported, and the separators coated with the second liquid may be brought into contact with the cooling rollers.

[0036] The method for interposing the inclusion between the electrode plate and the separator is not limited to the method of applying the second liquid, and may be, for example, a method of interposing a molded inclusion between the electrode plate and the separator. Since the melting point of the first compound contained in the inclusion is within the above-mentioned range, it is easy to form a solidified inclusion by cooling. Therefore, a molded sheet-shaped inclusion may be prepared as the solidified inclusion, and this molded sheet may be sandwiched between the electrode plate and the separator to interpose the inclusion between the electrode plate and the separator.

[0037] (Accommodating the electrode body (accommodating step)) In the accommodation step, the electrode assembly is accommodated in the outer casing. The temperature conditions for the accommodation step may be, for example, the same as those described above for the temperature conditions for the lamination step.

[0038] In the lamination step of this method, the electrode plates and separators are laminated with an interposing material interposed therebetween to obtain an electrode assembly in which the electrode plates and separators are in close contact with each other. This method allows the electrode assembly to be housed in an outer casing while suppressing misalignment between the electrode plates and separators.

[0039] (Injecting the first liquid (injection process)) In the liquid injection step, the first liquid is injected into the exterior housing containing the electrode assembly. The liquid injection step may be carried out, for example, at room temperature (e.g., 20 to 30°C) or within the temperature range described above for the lamination step.

[0040] The first liquid contains at least a portion of the remaining components contained in the non-aqueous electrolyte, and may contain all of the remaining components. As described above, the remaining components are the components remaining after excluding the components contained in the non-aqueous electrolyte in the inclusions from the components contained in the non-aqueous electrolyte. The first liquid preferably contains a portion of the solvent contained in the non-aqueous electrolyte, and more preferably contains a solvent contained in the non-aqueous electrolyte other than the first compound. The first liquid may contain the first compound, or may not contain the first compound. The first liquid may contain components other than the components contained in the non-aqueous electrolyte, but preferably contains only the components contained in the non-aqueous electrolyte.

[0041] The viscosity V1 [mPa·s] of the first solution is preferably smaller than the viscosity V0 [mPa·s] of the nonaqueous electrolyte. The difference (V0-V1) between the viscosities V0 and V1 can be adjusted by adjusting the value of the ratio (C1 / C0), and may be, for example, 0.2 to 2 mPa·s, 0.5 to 1.8 mPa·s, or 0.8 to 1.6 mPa·s. If the difference (V0-V1) is below the above range, it becomes difficult to improve the productivity of the battery using this method. If the difference (V0-V1) is above the above range, handling becomes difficult when interposing the first compound between the electrode plate and the separator.

[0042] The viscosity V1 of the first liquid may be, for example, 1.5 to 4 mPa·s, 1.8 to 3.8 mPa·s, 2 to 3.6 mPa·s, or 2.1 to 3.2 mPa·s. The viscosity V0 of the non-aqueous electrolyte may be, for example, 3 to 4.2 mPa·s, 3.3 to 4 mPa·s, or 3.5 to 3.8 mPa·s. In this specification, the viscosities of the first liquid and the non-aqueous electrolyte refer to kinematic viscosities, and refer to values ​​measured using a Stabinger viscometer at 25°C according to a method in accordance with ISO 23581:2020.

[0043] The present battery can be manufactured through the laminating step, the housing step, and the liquid injection step of this method. The present battery contains a nonaqueous electrolyte formed by mixing components in the inclusions with components in the first liquid. The nonaqueous electrolyte contains at least a first compound, and preferably contains components other than the first compound. The content of the first compound in the nonaqueous electrolyte is, for example, 1 to 7 mass %, and may be 1.5 to 7 mass %, 1.5 to 6 mass %, 2.5 to 5 mass %, or 3 to 4 mass %. When the nonaqueous electrolyte contains two or more types of first compounds, the content of the first compounds refers to the total amount of the first compounds contained in the nonaqueous electrolyte.

[0044] Each of the components constituting the present battery will be described in detail below. (electrode body) The electrode body may be a laminated electrode body in which a plurality of negative electrode plates and a plurality of positive electrode plates are alternately stacked with a separator interposed therebetween, or may be a wound electrode body in which a long laminate in which long negative electrode plates and long positive electrode plates are stacked with a long separator interposed therebetween is wound.

[0045] When the electrode body is a wound electrode body, the length in the direction of the winding axis may be 140 mm or more, 150 mm or more, 150 to 350 mm, 180 to 350 mm, or 200 to 300 mm. The length in the longer direction of the directions perpendicular to the winding axis of the wound electrode body may be 70 mm or more, 80 mm or more, 80 to 140 mm, or 90 to 120 mm.

[0046] When the electrode body is a laminated electrode body, the laminated electrode body preferably has a square or rectangular shape in plan view. In the laminated electrode body, the length in a direction parallel to one side of the square or the length in a direction parallel to the long side of the rectangle may be 140 mm or more, 150 mm or more, 150 to 350 mm, 180 to 350 mm, or 200 to 300 mm. The length in a direction parallel to the short side of the rectangle may be 70 mm or more, 80 mm or more, 80 to 140 mm, or 90 to 120 mm.

[0047] An electrode body having the above-mentioned length results in a large secondary battery size, making it difficult for the nonaqueous electrolyte to penetrate into the electrode body, and therefore the productivity of the secondary battery is likely to decrease. According to this method, even in secondary batteries having such large electrode bodies, the injection step makes it easier to uniformly distribute the first compound inside the electrode body in a short time, thereby improving the productivity of the secondary battery.

[0048] (Pole plate) The electrode plate is a positive electrode plate and / or a negative electrode plate. The positive electrode plate can have a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is, for example, a metal foil made of an aluminum material such as aluminum or an aluminum alloy. The positive electrode active material layer can be formed on one or both sides of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material such as a lithium transition metal oxide, and can further contain a conductive additive, a binder, etc. The positive electrode plate has a positive electrode active material layer side facing the separator.

[0049] The negative electrode plate can have a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is, for example, a metal foil made of a copper material such as copper or a copper alloy. The negative electrode active material layer can be formed on one or both sides of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material such as graphite, and can further contain a conductive additive, a binder, etc. The negative electrode plate has the negative electrode active material layer facing the separator.

[0050] The separator may have a substrate and a functional layer on at least one side of the substrate. The substrate may be a porous sheet and may have a single-layer structure or a multi-layer structure. Examples of the functional layer include an adhesive layer and a heat-resistant layer, and the separator may have one or both of these. The adhesive layer may be formed, for example, by an adhesive. The heat-resistant layer may contain, for example, a filler and a binder.

[0051] (Non-aqueous electrolyte) The non-aqueous electrolyte solution contains an electrolyte in a solvent and may further contain an additive, which is a compound other than the solvent and electrolyte. Examples of the electrolyte include lithium salts such as LiPF, LiBF, LiClO, LiFSO, and LiBOB (lithium bis(oxalato)borate).

[0052] The solvent is preferably a non-aqueous solvent such as an organic solvent. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), butylene carbonate (BC), diethyl carbonate (DEC), 3-methyloxazolidinone (MOX), γ-butyrolactone (BL), dimethyl sulfoxide (DMSO), sulfolane (S), and 1,3-propane sultone. The non-aqueous electrolyte may contain one or more of these non-aqueous solvents.

[0053] Examples of the additive include cyclic carbonate compounds having a carbon-carbon double bond, such as vinylene carbonate (VC) and vinylethylene carbonate (VEC), fluoroethylene carbonate, and salts such as oxalates, phosphates, and sulfates. The non-aqueous electrolyte may contain one or more of these additives.

[0054] (exterior body) The exterior body is a case that houses the electrode assembly and can be made of aluminum, an aluminum alloy, iron, an iron alloy, or the like. A resin sheet serving as an electrode holder may be disposed between the exterior body and the electrode assembly. The exterior body has an opening through which the electrode assembly is inserted. The opening of the exterior body may be sealed with a sealing plate to form a battery case. When the exterior body is a laminate film, a pouch-shaped battery case may be formed by overlapping and welding the edges of the laminate film. [Example]

[0055] Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples.

[0056] Comparative Example 1 An electrode assembly was obtained by stacking a positive electrode plate (electrode plate) and a negative electrode plate (electrode plate) with a separator interposed therebetween. A nonaqueous electrolyte solution containing LiPF6 as an electrolyte and a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (EC:EMC:DMC = 3:3:4 (volume ratio)) was prepared. The first compound contained in the nonaqueous electrolyte solution was EC (melting point: 39 to 40°C). The electrode assembly was housed in an outer casing, and a specific amount of nonaqueous electrolyte solution was poured into it. The electrode was removed from the outer casing at regular intervals to check the degree of wetting of the electrode plate. The time until it was confirmed that approximately 90% of the entire electrode plate was wet was measured as the pouring time.

[0057] Example 1 A secondary battery including a nonaqueous electrolyte solution, electrode assembly, and exterior case with the same composition as in Comparative Example 1 was fabricated by the following procedure. EC (second liquid) was applied to the surface of the separator facing the electrode plates (positive and negative electrode plates). The applied EC (intercalator) was interposed between the electrode plates and the separator, and the resulting stack was used to obtain an electrode assembly (stacking step). The electrode assembly was housed in an exterior case (accommodating step). A first liquid was prepared from the components contained in the nonaqueous electrolyte, excluding the EC interposed between the electrode plates and the separator. A specific amount of the first liquid was injected into the exterior case housing the electrode assembly (liquid injection step). The electrodes were removed from the exterior case at regular intervals, and the degree of wetting of the electrode plates was confirmed. The time until it was confirmed that approximately 90% of the entire electrode plates were wet was measured as the liquid injection time. The ratio (C1 / C0) of the EC content C1 [parts by mass] in the applied EC to the EC content C0 [parts by mass] in the nonaqueous electrolyte was 100 / 100.

[0058] Example 2 A secondary battery was fabricated using the same procedure as in Example 1, except that the ratio (C1 / C0) of the EC content C1 [parts by mass] in the applied EC to the EC content C0 [parts by mass] in the non-aqueous electrolyte was set to 10 / 100.

[0059] [Evaluation of improvement rate of time required for injection process] The ratio of the injection time of the first liquid in Examples 1 and 2 to the injection time of the nonaqueous electrolyte in Comparative Example 1 was calculated using the following formula, and this was taken as the improvement rate of the time required for the injection step. The results are shown in Table 1. Improvement rate [%] = [(non-aqueous electrolyte injection time - first liquid injection time) / non-aqueous electrolyte injection time] x 100

[0060] [Table 1]

Claims

1. A method for manufacturing a non-aqueous electrolyte secondary battery including an electrode assembly in which electrode plates and a separator are stacked, a non-aqueous electrolyte solution, and an exterior body that accommodates the electrode assembly and the non-aqueous electrolyte solution, obtaining the electrode assembly by stacking the electrode plates and the separators with an intervening material therebetween; The electrode assembly is housed in the outer casing; and injecting a first liquid into the exterior housing that houses the electrode assembly; the inclusions are components constituting the nonaqueous electrolyte solution and contain a compound having a melting point of 15 to 45°C; the first liquid contains at least a portion of the remaining components obtained by excluding the components contained in the nonaqueous electrolyte solution in the inclusions from the components contained in the nonaqueous electrolyte solution, a ratio (C1 / C0) of a content C1 [parts by mass] of the compound in the inclusions to a content C0 [parts by mass] of the compound in the nonaqueous electrolyte solution is 100 / 100 to 8 / 100.

2. Obtaining the electrode assembly includes: Applying a second liquid containing the inclusions to at least one of the electrode plate and the separator; and The method for manufacturing a nonaqueous electrolyte secondary battery according to claim 1 , further comprising: interposing the applied second liquid between the electrode plate and the separator.

3. The method for manufacturing a nonaqueous electrolyte secondary battery according to claim 2 , further comprising cooling the applied second liquid to reduce the fluidity of the second liquid.

4. 3. The method for producing a nonaqueous electrolyte secondary battery according to claim 2, further comprising cooling the applied second liquid to within ±5°C of the melting point of the compound.

5. 5. The method for producing a non-aqueous electrolyte secondary battery according to claim 3, further comprising bringing the separator coated with the second liquid into contact with a cooling roller.

6. the separator is a long separator, The method for producing a nonaqueous electrolyte secondary battery according to claim 5 , further comprising applying the second liquid to the separator while it is being transported.

7. 2 . The method for producing a nonaqueous electrolyte secondary battery according to claim 1 , wherein the inclusions are present in the center of the surface where the electrode plate and the separator face each other, and are not present in at least a part of the edge portions.

8. The method for producing a non-aqueous electrolyte secondary battery according to claim 1 , wherein the inclusions are present on the entire surface where the electrode plate and the separator face each other.

9. The method for producing a non-aqueous electrolyte secondary battery according to claim 1 , wherein the inclusions contain ethylene carbonate.

10. The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 1 , wherein the first liquid contains a part of the solvent contained in the non-aqueous electrolyte solution.

11. 2. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the content of said compound in said non-aqueous electrolyte solution is 1 to 7 mass %.

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