Manufacturing method for non-aqueous electrolyte secondary battery

Abstract

To provide a non-aqueous electrolyte secondary battery using an electrolytic solution containing a compound (F) having a -SO2F group, capable of suppressing an increase in a reaction resistance in a central part of a negative electrode.SOLUTION: A manufacturing method of a non-aqueous electrolyte secondary battery including an electrode assembly and an electrolyte solution includes: a first step of pouring a first electrolyte solution including a compound (F) having a -SO2F group into an exterior body accommodating the electrode assembly to obtain a battery assembly; and a second step of pouring a second electrolyte solution into the exterior body of the battery assembly after the first step. A content of the compound (F) in the second electrolytic solution is 10 mass% or less with respect to a total amount of the compound (F) in the electrolytic solution of the non-aqueous electrolyte secondary battery, and is smaller than the content of the compound (F) in the first electrolytic solution.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] Patent Document 1 discloses that a compound having a fluorosulfonyl structure (-SOF group) is added to the electrolyte of a non-aqueous electrolyte battery. Patent Document 1 also discloses that the cycle characteristics of the battery can be improved by including the compound in the electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 157591 Summary of the Invention [Problem to be solved by the invention]

[0004] It was found that when an electrolyte containing a compound having a -SO2F group is used, the reaction resistance increases in the center of the negative electrode when viewed from above.

[0005] The present disclosure aims to suppress an increase in reaction resistance at the center of the negative electrode in a nonaqueous electrolyte secondary battery using an electrolyte solution containing a compound (F) having a -SO2F group. [Means for solving the problem]

[0006] [1] A method for manufacturing a nonaqueous electrolyte secondary battery including an electrode assembly and an electrolyte solution, a first step of obtaining a battery assembly by injecting a first electrolytic solution containing a compound (F) having a —SOF group into an exterior housing that accommodates the electrode body; a second step of injecting a second electrolytic solution into the exterior body of the battery assembly after the first step, The content of the compound (F) in the second electrolytic solution is 10% by mass or less of the total amount of the compound (F) in the electrolyte solution of the nonaqueous electrolyte secondary battery, and the content of the compound (F) in the first electrolytic solution is smaller than that in the second electrolytic solution. [2] The method for producing a nonaqueous electrolyte secondary battery according to [1], wherein the content of the compound (F) in the first electrolytic solution is 90 mass % or more based on the total amount of the compound (F) in the electrolytic solution of the nonaqueous electrolyte secondary battery. [3] The method for producing a nonaqueous electrolyte secondary battery according to [1] or [2], wherein an amount of the first electrolytic solution injected in the first step is 50 mass % or more with respect to a total amount of the electrolytic solution in the nonaqueous electrolyte secondary battery. [4] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [3], wherein the second electrolytic solution does not contain the compound (F). [5] The method for producing a non-aqueous electrolyte secondary battery according to any one of [1] to [4], wherein the compound (F) is a fluorosulfonate. [6] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [5], wherein the compound (F) contains LiFSO3. [7] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [6], further comprising a step of pressurizing the battery assembly after the second step. [8] The electrode body is a wound electrode body or a laminated electrode body including a negative electrode having an active material layer, The length of the active material layer in the direction of the winding axis of the wound electrode body is 140 mm or more, The laminated electrode body has a square or rectangular shape in plan view, [1] to [7], wherein the length of the active material layer in a direction parallel to one side of the square or a direction parallel to a short side of the rectangle is 140 mm or more. [9] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [8], wherein the second electrolytic solution contains one or more electrolytes selected from the group consisting of LiPF6, LiBF4, and LiBOB.

[10] The method for producing a nonaqueous electrolyte secondary battery according to any one of [1] to [9], wherein the first electrolytic solution contains one or more electrolytes selected from the group consisting of LiPF6, LiBF4, and LiBOB. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to manufacture a nonaqueous electrolyte secondary battery that can suppress an increase in reaction resistance in the center of the negative electrode when viewed from above the electrode assembly. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a flowchart showing a method for manufacturing 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 "x to y" includes both the upper and lower limits. That is, "x to y" represents a numerical range of "greater than or equal to x and less than or equal to y." 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 showing a method for manufacturing a nonaqueous electrolyte secondary battery according to an embodiment. The nonaqueous electrolyte secondary battery according to this embodiment (hereinafter also referred to as "the battery") is, for example, a lithium ion secondary battery that charges and discharges by absorbing and releasing lithium ions.

[0011] The present battery includes an electrode assembly and an electrolyte. The method for manufacturing the present battery (hereinafter also referred to as the "method") includes: a first step of obtaining a battery assembly by injecting a first electrolytic solution containing a compound (F) having a -SOF group (hereinafter also referred to as "compound (F)") into an exterior housing containing an electrode assembly; a second step of injecting a second electrolytic solution into the exterior body of the battery assembly after the first step, The content of compound (F) in the second electrolytic solution is 10 mass % or less relative to the total amount of compound (F) in the electrolytic solution of the battery, and is smaller than the content of compound (F) in the first electrolytic solution.

[0012] In this method, the injection step of injecting the electrolyte solution into the exterior body may be Step 1 and Step 2, or may include one or more injection steps other than Step 1 and Step 2 (hereinafter also referred to as "other injection steps"). In addition, this method may include a step of housing an electrode assembly in the exterior body before Step 1; a depressurizing step of reducing the pressure inside a chamber container housing a battery assembly and holding the battery assembly; a holding step of holding the battery assembly into which the electrolyte solution has been injected at atmospheric pressure; a pressurizing step of pressurizing the battery assembly, etc.

[0013] The electrode assembly typically includes a positive electrode and a negative electrode. The positive electrode has a positive electrode active material layer containing a positive electrode active material, and the negative electrode has a negative electrode active material layer (active material layer) containing a negative electrode active material. The electrode assembly may, for example, include a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0014] The electrolyte solution containing compound (F) can form a coating with low reaction resistance on the surface of the negative electrode active material. The -SO2F group of compound (F) is likely to adsorb to the negative electrode active material, and it is presumed that compound (F) penetrates more slowly into the center of the electrode assembly in a planar view than electrolytes other than the nonaqueous solvent and compound (F) contained in the electrolyte solution. The center of the electrode assembly in a planar view (hereinafter simply referred to as the "center") refers to the central portion of the electrode assembly when viewed from the stacking direction of the positive electrode, negative electrode, and separator. Therefore, it is difficult for a coating to form on the surface of the negative electrode active material in the center of the negative electrode, and reaction resistance in the center of the negative electrode is likely to increase.

[0015] In contrast, in this method, in the first step, a first electrolytic solution containing compound (F) is injected into an exterior housing housing an electrode assembly, and in the second step, a second electrolytic solution having a lower compound (F) content than the first electrolytic solution is injected into the exterior housing. In this way, in this method, a first electrolytic solution containing a large amount of compound (F), which penetrates slowly into the center of the electrode assembly, is injected, followed by a second electrolytic solution with a lower compound (F) content. This allows compound (F) in the first electrolytic solution injected in the first step to more easily penetrate into the center of the electrode assembly in the second step. This is thought to suppress uneven distribution of compound (F) within the electrode assembly and facilitate the formation of a uniform coating on the surface of the negative electrode active material throughout the entire negative electrode. This suppresses an increase in reaction resistance in the center of the negative electrode.

[0016] (1st step) The first step is a step of injecting a first electrolytic solution containing compound (F) into an exterior housing that houses an electrode assembly to obtain a battery assembly. The battery assembly has an electrode assembly and an exterior housing, and may further have a sealing plate that seals the opening of the exterior housing. In the first step, the first electrolytic solution can be injected into the exterior housing through the opening of the exterior housing or through an injection hole formed in the sealing plate. Of the steps of injecting an electrolytic solution into an exterior housing that are performed in this method, the first step is preferably the first step of injecting an electrolytic solution containing compound (F), and more preferably the first step of injecting an electrolytic solution.

[0017] The first electrolytic solution is usually a non-aqueous electrolytic solution, preferably a non-aqueous solvent such as an organic solvent, containing compound (F) and an electrolyte other than compound (F). The first electrolytic solution contains compound (F) in a content greater than the content of compound (F) in the second electrolytic solution. The content of compound (F) in the first electrolytic solution is the amount of compound (F) contained in the total amount of the first electrolytic solution injected in the first step, and the content of compound (F) in the second electrolytic solution is the amount of compound (F) contained in the total amount of the second electrolytic solution injected in the second step.

[0018] The amount of the first electrolytic solution injected in the first step is preferably 50% by mass or more, and may be 50 to 90% by mass, 55 to 85% by mass, or 60 to 80% by mass, relative to the total amount of the electrolytic solution in the battery. The electrolytic solution in the battery refers to all electrolytic solutions injected in the method, and if the method includes other injection steps, it also includes the electrolytic solutions injected in the other injection steps in addition to the first and second electrolytic solutions. In the first step, the first electrolytic solution is preferably injected in an amount such that the entire electrode assembly is immersed in the first electrolytic solution in the exterior packaging immediately after the injection of the entire amount of the first electrolytic solution has been completed.

[0019] Compound (F) is a compound having a -SO2F group. Examples of compound (F) include fluorosulfonates.

[0020] Examples of the salt form of the fluorosulfonate include alkali metal salts such as lithium salt, sodium salt, potassium salt, rubidium salt, and cesium salt; alkaline earth metal salts such as magnesium salt, calcium salt, and barium salt; and ammonium salt. The fluorosulfonate is, for example, one or more selected from the group consisting of LiFSO3, NaFSO3, KFSO3, RbFSO3, and CsFSO3. Compound (F) is preferably LiFSO3.

[0021] The content of compound (F) in the first electrolytic solution is greater than the content of compound (F) in the second electrolytic solution. The content of compound (F) in the first electrolytic solution is preferably 90 mass % or more, may be 95 mass % or more, may be 100 mass %, may be 90 to 100 mass %, may be 95 to 99 mass %, or may be 95 to 98 mass %, based on the total amount of compound (F) in the electrolytic solution of the battery.

[0022] Examples of electrolytes other than compound (F) contained in the first electrolytic solution include electrolytes contained in known electrolytic solutions used in nonaqueous electrolyte secondary batteries (hereinafter also referred to as "batteries"). The first electrolytic solution preferably contains, as the electrolyte other than compound (F), one or more electrolytes selected from the group consisting of LiPF6, LiBF4, and LiBOB, and more preferably LiPF6.

[0023] Examples of non-aqueous solvents that may be contained in the first electrolytic solution include ethylene carbonate (EC), dimethyl carbonate (DMC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). The first electrolytic solution may contain one or more of these non-aqueous solvents, preferably at least one of EC, DMC, and EMC, and more preferably a mixed solvent containing EC and EMC. The non-aqueous solvent used in the first electrolytic solution preferably contains two or more of EC, DMC, and EMC in a volume ratio of EC:DMC:EMC=5-40:0-70:0-70, or may contain EC:DMC:EMC=10-40:20-70:0-50, or may contain EC:EMC=30-40:60-70.

[0024] (2nd process) The second step is a step of injecting a second electrolytic solution into the exterior body of the battery assembly after the first step. The second step may be performed after the first step, but is preferably performed without performing any other injection steps between the first and second steps. The second step may be performed after the depressurization step and the retention step have been performed after the first step. In the second step, the second electrolytic solution may be injected into the exterior body through the injection hole formed in the sealing plate.

[0025] The second electrolytic solution is usually a non-aqueous electrolytic solution and can be prepared using an electrolyte other than compound (F) and a non-aqueous solvent as described for the first electrolytic solution. The electrolyte other than compound (F) and the non-aqueous solvent contained in the second electrolytic solution are preferably the same as the electrolyte other than compound (F) and the non-aqueous solvent contained in the first electrolytic solution. The second electrolytic solution preferably contains one or more electrolytes selected from the group consisting of LiPF6, LiBF4, and LiBOB, and more preferably contains LiPF6.

[0026] The content of compound (F) in the second electrolytic solution is preferably 10% by mass or less, or may be 5% by mass or less, or may be 0 to 10% by mass, or may be 0 to 5% by mass, or may be 1 to 5% by mass, based on the total amount of compound (F) in the electrolytic solution of the battery. The second electrolytic solution more preferably does not contain compound (F). The content of compound (F) in the second electrolytic solution is smaller than the content of compound (F) in the first electrolytic solution.

[0027] The amount of the second electrolytic solution injected in the second step is, for example, 50 mass % or less, or may be 10 to 50 mass %, 15 to 45 mass %, or 20 to 40 mass % relative to the total amount of the electrolytic solution in the battery.

[0028] (Other injection processes) The other liquid injection step is a step of injecting an electrolyte into the exterior body. The other liquid injection step is preferably carried out within the range of liquid injection conditions described in the second step, and as long as it is within this range, the liquid injection conditions may be the same as or different from those in the second step. The electrolyte used in the other liquid injection step more preferably does not contain compound (F). The other liquid injection step is preferably carried out after the first step, and can be carried out, for example, at least one stage between the first step and the second step, or after the second step. This allows compound (F) to further penetrate into the center of the electrode body. The present method does not necessarily include the other liquid injection step.

[0029] (Decompression process) The depressurization step is a step of maintaining the battery assembly under reduced pressure, and can be carried out, for example, by reducing the pressure inside a chamber container that houses the battery assembly. The depressurization step is carried out for the purposes of removing gas from the battery assembly and permeating the electrolyte into the electrode body. The depressurization step is preferably carried out after the first step and / or the second step, or between the first and second steps. The depressurization step may be repeated two or more times. When the depressurization step is repeated two or more times, the pressure inside the chamber container is returned to atmospheric pressure after the first depressurization step, and the chamber container is again maintained under reduced pressure. The gauge pressure in the depressurization step is, for example, -80 to -10 kPa, or may be -70 to -20 kPa, or may be -60 to -30 kPa. The time for maintaining the reduced pressure state is, for example, 0.1 to 10 minutes, or may be 0.5 to 5 minutes, or may be 1 to 3 minutes.

[0030] (holding process) The holding step is a step of holding the battery assembly under atmospheric pressure, and is carried out for the purpose of impregnating the electrode body with the electrolyte. The holding step can be carried out after the electrolyte is injected and / or after the pressure is reduced to atmospheric pressure. The holding step can be carried out under atmospheric pressure at room temperature (e.g., 20 to 25°C), and the holding time is, for example, 0.5 to 3 hours, or may be 1 to 2 hours.

[0031] (Pressure process) The pressurizing step is a step of pressurizing the battery assembly, and can be carried out, for example, by pressurizing the chamber container housing the battery assembly. In the pressurizing step, a force is applied that pushes the electrolyte into the electrode body, further promoting the penetration of compound (F). The pressurizing step is preferably carried out after the second step. The gauge pressure in the pressurizing step is, for example, 0.1 to 1 MPa, or may be 0.3 to 0.8 MPa, or may be 0.4 to 0.6 MPa. The pressurizing step can be carried out, for example, by sealing nitrogen in the chamber container. The time for which the pressurized state is maintained is, for example, 0.5 to 3 hours, or may be 1 to 2 hours.

[0032] (electrode body) As described above, the electrode assembly may include, for example, a positive electrode plate, a negative electrode plate, and a separator. The electrode assembly may be a wound type electrode assembly or a stacked type electrode assembly.

[0033] When the electrode body is a wound electrode body, the length of the negative electrode active material layer in the direction parallel to the winding axis may be 140 mm or more, preferably 150 mm or more, and may be 150 mm or more and 350 mm or less, 180 mm or more and 350 mm or less, or 200 mm or more and 300 mm or less. When the electrode body is a stacked electrode body, the stacked electrode body preferably has a square or rectangular shape in plan view. In this case, in the stacked electrode body, the length of the negative electrode active material layer in the direction parallel to one side of the square or the length of the negative electrode active material layer in the direction parallel to the short side of the rectangle may be 140 mm or more, preferably 150 mm or more, and may be 150 mm or more and 350 mm or less, 180 mm or more and 350 mm or less, or 200 mm or more and 300 mm or less.

[0034] In a large battery having a negative electrode active material layer of the above-mentioned length, compound (F) is unevenly distributed within the electrode body, and the reaction resistance at the center of the negative electrode is likely to increase. According to the method of the present battery, even when the negative electrode active material layer has the above-mentioned length, it is easy to form a coating evenly on the surface of the negative electrode active material over the entire negative electrode, and the increase in reaction resistance at the center of the negative electrode can be suppressed.

[0035] The negative electrode may have a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. 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 contains a negative electrode active material. Examples of the negative electrode active material include carbon-based active materials containing carbon (C) atoms, such as graphite; and metal-based active materials containing metal elements, such as simple metals or metal oxides, containing elements selected from the group consisting of silicon (Si), tin (Sn), antimony (Sb), bismuth (Bi), titanium (Ti), and germanium (Ge). The negative electrode active material layer may contain a Si-based active material containing silicon.

[0036] The negative electrode active material layer may contain, in addition to the negative electrode active material, one or both of a binder and a conductive additive. Examples of binders include cellulose-based binders such as carboxymethyl cellulose (CMC), methyl cellulose (MC), and hydroxypropyl cellulose; styrene butadiene rubber (SBR), polyacrylic acid (PAA), acrylonitrile butadiene rubber (NBR), polyvinylidene fluoride (PVdF), and polytetrafluoroethylene (PTFE). Examples of conductive additives include carbon materials such as fibrous carbon, carbon black (acetylene black, ketjen black, etc.), coke, and activated carbon. Examples of fibrous carbon include carbon nanotubes (hereinafter also referred to as "CNTs"). CNTs may be single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes such as double-walled carbon nanotubes (DWCNTs).

[0037] The positive electrode may have a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. 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 contains a positive electrode active material. Examples of the positive electrode active material include lithium transition metal composite oxides (e.g., LiNiCoMnO2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, LiCrMnO4, LiFePO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) are examples.

[0038] The positive electrode active material layer may contain, in addition to the positive electrode active material, one or both of a binder and a conductive additive. Examples of the binder include SBR, PVdF, and PTFE. Examples of the conductive additive include those described above.

[0039] The separator may be a porous sheet (film, nonwoven fabric, etc.) made of a resin such as polyethylene, polypropylene, polyester, cellulose, or polyamide. The porous sheet may have a single-layer structure or a multi-layer structure of two or more layers. The separator may have a functional layer on the surface of the porous sheet. The functional layer may be at least one of a heat-resistant layer and an adhesive layer for adhering to the positive electrode plate and the negative electrode plate.

[0040] (exterior body) The exterior body is a housing that houses the electrode assembly and has an opening for housing the electrode assembly. The opening of the exterior body can be sealed with a sealing plate. The exterior body and the sealing plate are preferably made of metal and can be formed using aluminum, an aluminum alloy, iron, an iron alloy, or the like, and can be formed using, for example, an aluminum laminate film. [Example]

[0041] Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples. Example 1 (Preparation of positive electrode) A cathode active material, LiNiCoMnO2, a conductive additive, acetylene black (AB), and a binder, polyvinylidene fluoride (PVdF), were used in a mass ratio of LiNiCoMnO2:AB:PVdF = 100:1:1. This mixture was mixed with N-methylpyrrolidone (NMP) to obtain a cathode mixture slurry. The cathode mixture slurry was applied to an aluminum foil current collector, dried, and compressed to a predetermined thickness to form a cathode active material layer on the aluminum foil. The cathode was then cut to a predetermined width to obtain a cathode. The cathode had a widthwise region where the cathode active material layer was formed on the aluminum foil and a region where the cathode active material layer was not formed and the aluminum foil was exposed. The width of the cathode active material layer (the length parallel to the winding axis of the electrode body) of the cathode active material layer was 146 mm.

[0042] (Preparation of negative electrode) Graphite was used as the negative electrode active material, and styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were used as binders in a graphite:SBR:CMC = 100:1:1 (mass ratio). This was mixed with water to obtain a negative electrode mixture slurry. The negative electrode mixture slurry was applied to a copper foil negative electrode current collector, dried, and compressed to a predetermined thickness to form a negative electrode active material layer on the copper foil. The negative electrode was then cut to a predetermined width to obtain a negative electrode. The negative electrode had a region in the width direction where the negative electrode active material layer was formed on the copper foil and a region where the negative electrode active material layer was not formed and the copper foil was exposed. The width of the negative electrode active material layer (length in the direction parallel to the winding axis of the electrode body) was 150 mm.

[0043] (Preparation of electrode body) A separator with a three-layer structure of polypropylene (PP) / polyethylene (PE) / PP was prepared. The positive and negative electrodes obtained above were stacked with the separator interposed between them and wound to obtain a wound electrode body. An aluminum plate for external current collection was welded to the area where the positive electrode current collector of the wound electrode body was exposed, and a copper plate for external current collection was welded to the area where the negative electrode current collector was exposed, thereby integrating the wound electrode body with the sealing plate of the battery case.

[0044] (Preparation of electrolyte (1)) Using LiFSO3 as the compound (F), LiPF6 as the electrolyte, and a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC = 1:3 (volume ratio)) as the non-aqueous solvent, LiFSO3, LiPF6, and the mixed solvent were mixed so that the concentration of LiPF6 was 1 mol / L and the concentration of LiFSO3 was 1.43 mass%, to prepare an electrolyte solution (1).

[0045] (Preparation of electrolyte (2)) Electrolyte solution (2) was prepared by mixing LiPF6 as the electrolyte and a mixed solvent of EC and EMC (EC:EMC = 1:3 (volume ratio)) as the non-aqueous solvent so that the concentration of LiPF6 was 1 mol / L.

[0046] (Preparation of electrolyte (3)) An electrolyte solution (3) was prepared with the same composition as the electrolyte solution (1), except that the concentration of LiFSO3 was adjusted to 1 mass %.

[0047] (Fabrication of non-aqueous electrolyte secondary battery) The wound electrode body integrated with the sealing plate was housed in an aluminum exterior body, and the exterior body and the sealing plate were welded. Under a nitrogen atmosphere, electrolyte solution (1) as the first electrolyte solution was poured through an inlet provided in the sealing plate in an amount of 70 mass % relative to the total amount of electrolyte in the battery to obtain a battery assembly (first step). The battery assembly was placed in a chamber container, and the pressure was reduced to -50 kPa and maintained for 1 minute (depressurization step), followed by returning to atmospheric pressure. This operation was repeated twice. Next, a temporary sealing plug was inserted into the inlet, and the battery was left standing for 1 hour in an environment of 25°C (maintenance step). The temporary sealing plug was removed, and under a nitrogen atmosphere, electrolyte solution (2) as the second electrolyte solution was poured through the inlet in an amount of 30 mass % relative to the total amount of electrolyte in the battery (second step). The battery assembly after the second step was placed in a chamber container, and nitrogen was sealed in to a gauge pressure of 0.5 MPa, and the pressure was maintained for 1 hour (pressurization step), and then returned to atmospheric pressure. The battery assembly was then placed in a chamber container, and the pressure was reduced to -50 kPa, and the pressure was maintained for 1 minute (depressurization step), and the pressure was returned to atmospheric pressure. This cycle was repeated twice. A sealing plug was then attached to the injection hole and welded, and the battery was then left in an environment of 25°C for 1 hour (maintenance step), to obtain a battery. The electrolyte solution (1) injected in the first injection step contained compound (F), but the electrolyte solution (2) injected in the second injection step did not contain compound (F). Therefore, the concentration of compound (F) in the battery's electrolyte was 1% by mass.

[0048] Comparative Example 1 A battery assembly was obtained by injecting the electrolyte (2) in an amount of 100 mass % of the total amount of the electrolyte in the battery in the first liquid injection step, and a battery was obtained in the same procedure as in Example 1, except that the second liquid injection step was not performed. The electrolyte in the battery did not contain compound (F).

[0049] Comparative Example 2 A battery assembly was obtained by injecting the electrolyte (3) in an amount of 100% by mass relative to the total amount of the electrolyte in the battery in the first liquid injection step, and a battery was obtained in the same procedure as in Example 1, except that the second liquid injection step was not performed. The concentration of compound (F) in the electrolyte in the battery was 1% by mass.

[0050] Example 2 A battery was obtained in the same manner as in Example 1, except that the pressurizing step was not carried out.

[0051] [Comparative Example 3 and Example 3] A battery was obtained in the same manner as in Comparative Example 2 and Example 1, except that the width of the positive electrode active material layer of the positive electrode was 76 mm and the width of the negative electrode active material layer of the negative electrode was 80 mm.

[0052] [Measurement of reaction resistance at the center of the negative electrode] The battery obtained above was charged to 4.2 Vcccv (constant current / constant voltage) at a current value of C / 10 in an environment of 25°C, and then stored at 60°C for 24 hours. After that, the battery was initially activated by discharging to a voltage of 3 V at a current value of C / 10.

[0053] After initial activation, the battery was disassembled, and a 10 mm diameter piece was punched out from the center of the width direction (parallel to the winding axis) of the negative electrode, which faced the inner periphery of the first winding of the positive electrode (the inner periphery of the wound electrode body). The punched negative electrode was washed with dimethyl carbonate (DMC), dried under reduced pressure, and one side of the negative electrode was peeled off to obtain a negative electrode sample. An electrode body was fabricated by placing the negative electrode sample and an 11 mm diameter Li metal opposite each other through a separator with a 13 mm diameter and a PP / PE / PP layer structure. The electrode body was placed in a case, and electrolyte (2) was poured into it to fabricate a coin cell.

[0054] In a 25°C environment, the negative electrode of the coin cell was charged to 0.02 V at a current of 0.1 C, and the charge amount was defined as 100% SOC (state of charge). The negative electrode was discharged to 1 V at a current of 0.1 C and charged in the negative electrode charging direction so that the SOC was 50%. After resting for 1 hour in a 25°C environment, the AC impedance was measured in this state at 25°C, with an amplitude of 10 mV and in the range of 100 kHz to 0.1 Hz, and the range of 1 kHz to 1 Hz was defined as the negative electrode reaction resistance. The negative electrode reaction resistances of the examples and comparative examples were determined as relative values, with the negative electrode reaction resistance of Comparative Example 1 set as the reference (100%). The results are shown in Table 1.

[0055] [Table 1]

[0056] A comparison of the reaction resistance of the negative electrode in Comparative Examples 1 and 2 reveals that the compound (F) penetrates slowly into the electrode assembly. In Examples 1 to 3, the first and second steps promoted the penetration of the compound (F) into the center of the electrode assembly, which is thought to have reduced the reaction resistance of the negative electrode compared to Comparative Examples 1 and 2. A comparison of Examples 1 and 2 reveals that the pressurization step promotes the penetration of the compound (F) and can suppress an increase in the reaction resistance of the negative electrode. A comparison of Examples 1 and 2 with Example 3 and Comparative Example 3 reveals that in electrode assemblies with large negative electrode widths, the compound (F) does not penetrate easily into the center, which tends to increase the reaction resistance in the center of the negative electrode, but that the first and second steps promote the penetration of the compound (F) into the center of the electrode assembly.

Claims

1. A method for manufacturing a nonaqueous electrolyte secondary battery including an electrode assembly and an electrolyte solution, The outer casing housing the electrode assembly contains -SO ２ a first step of injecting a first electrolytic solution containing a compound (F) having an F group to obtain a battery assembly; a second step of injecting a second electrolytic solution into the exterior body of the battery assembly after the first step, The content of the compound (F) in the second electrolytic solution is The compound (F) is 10% by mass or less relative to the total amount of the compound (F) in the electrolyte solution of the nonaqueous electrolyte secondary battery, and the content of the compound (F) in the first electrolytic solution is smaller than that in the second electrolytic solution.

2. 2. The method for producing a nonaqueous electrolyte secondary battery according to claim 1, wherein a content of the compound (F) in the first electrolytic solution is 90 mass% or more with respect to a total amount of the compound (F) in the electrolytic solution of the nonaqueous electrolyte secondary battery.

3. 3 . The method for producing a nonaqueous electrolyte secondary battery according to claim 1 , wherein an amount of the first electrolytic solution injected in the first step is 50 mass % or more with respect to a total amount of the electrolytic solution in the nonaqueous electrolyte secondary battery.

4. The method for producing a nonaqueous electrolyte secondary battery according to claim 1 , wherein the second electrolytic solution does not contain the compound (F).

5. The method for producing a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the compound (F) is a fluorosulfonate.

6. The compound (F) is LiFSO ３ The method for producing a nonaqueous electrolyte secondary battery according to claim 1 or 2, comprising:

7. 3. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, further comprising the step of pressurizing the battery assembly after the second step.

8. the electrode body is a wound electrode body or a laminated electrode body including a negative electrode having an active material layer, the length of the active material layer in the direction of the winding axis of the wound electrode body is 140 mm or more; The laminated electrode body has a square or rectangular shape in plan view, 3. The method for producing a nonaqueous electrolyte secondary battery according to claim 1, wherein the length of the active material layer in a direction parallel to one side of the square or a direction parallel to a short side of the rectangle is 140 mm or more.

9. The second electrolyte solution is LiPF ６ , LiBF ４ 3. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery contains one or more electrolytes selected from the group consisting of LiBOB and LiBOB.

10. The first electrolyte solution is LiPF ６ , LiBF ４ 3. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery contains one or more electrolytes selected from the group consisting of LiBOB and LiBOB.

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