Method for manufacturing secondary battery and method for manufacturing doped electrode

Abstract

The present invention is a manufacturing method for a secondary battery in which a doped electrode including an active material layer doped with an alkali metal is used. The doped electrode is manufactured by transporting an electrode, containing an active material layer, along a path passing through a doping tank containing a counter electrode unit and a doping solution containing ions of the alkali metal and an aprotonic organic solvent. The secondary battery is manufactured by causing the doped electrode that has come out from the doping tank to be dried so as to contain 5 parts by mass to 40 parts by mass of a component of the doping solution with respect to 100 parts by mass of the active material layer, and then using the dried doped electrode.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This international application claims priority based on Japanese Patent Application No. 2020-187146 filed with the Japan Patent Office on November 10, 2020, the entire contents of which are incorporated by reference into this international application. [Technical field]

[0002] The present disclosure relates to a method for manufacturing a secondary battery and a method for manufacturing a doped electrode. [Background technology]

[0003] As electronic devices have become increasingly smaller and lighter in recent years, there is an increasing demand for smaller and lighter batteries to be used as the power source for these devices.

[0004] In order to satisfy such demands for miniaturization and weight reduction, non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, have been developed. In addition, lithium ion capacitors are known as power storage devices that can be used in applications that require high energy density and high output. Furthermore, sodium ion batteries and capacitors are also known that use sodium, which is less expensive and more abundant than lithium.

[0005] In such batteries and capacitors, a process of doping an electrode with an alkali metal in advance is adopted for various purposes. This process is generally called pre-doping. As a method of pre-doping an electrode with an alkali metal, for example, there is a continuous method. In the continuous method, pre-doping is performed while a strip-shaped electrode is transported in a doping solution. The continuous method is disclosed in Patent Documents 1 to 4. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-308212 [Patent Document 2] JP 2008-77963 A [Patent Document 3] JP 2012-49543 A [Patent Document 4] JP 2012-49544 A Summary of the Invention [Problem to be solved by the invention]

[0007] An electrode including an active material layer doped with an alkali metal is hereinafter referred to as a doped electrode. When the doped electrode leaves the tank of the doped solution, the components of the doped solution are attached to the doped electrode. As a result of research, the inventor has found that a secondary battery with high battery stability can be manufactured by using a doped electrode to which an appropriate amount of the components of the doped solution are attached. In one aspect of the present disclosure, it is preferable to provide a method for manufacturing a secondary battery with high battery stability and a method for manufacturing a doped electrode. [Means for solving the problem]

[0008] One aspect of the present disclosure is a method for producing a secondary battery using a doped electrode including an active material layer doped with an alkali metal. In the method for producing a secondary battery, the doped electrode is produced by conveying an electrode including an active material layer along a path passing through a doping solution including ions of the alkali metal and an aprotic organic solvent, and a doping tank that contains a counter electrode unit, and the doped electrode taken out of the doping tank is dried so that the doped electrode contains 5 parts by mass or more and 40 parts by mass or less of the components of the doping solution relative to 100 parts by mass of the active material layer, and the secondary battery is produced using the doped electrode after drying.

[0009] According to this manufacturing method, a secondary battery with high battery stability can be manufactured.

[0010] Another aspect of the present disclosure is a method for producing a doped electrode including an active material layer doped with an alkali metal, comprising the steps of: transporting an electrode including an active material layer along a path passing through a doping solution including ions of the alkali metal and an aprotic organic solvent, and a doping tank that contains a counter electrode unit, and drying the doped electrode that has been removed from the doping tank so that the doped electrode contains 5 to 40 parts by mass of the doping solution relative to 100 parts by mass of the active material layer.

[0011] By using a doped electrode produced by the method for producing a doped electrode according to another aspect of the present disclosure, a secondary battery with high battery stability can be produced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a plan view showing the configuration of an electrode 1. [Diagram 2] 2 is a cross-sectional view showing a cross section taken along line II-II in FIG. [Diagram 3] FIG. 2 is an explanatory diagram showing the configuration of an electrode manufacturing system 11. [Figure 4] FIG. 2 is an explanatory diagram showing the configuration of a doping tank 17. [Diagram 5] 2 is an explanatory diagram showing the configuration of counter electrode units 137 and 139. FIG. [Explanation of symbols]

[0013] 1...electrode, 1A...doped electrode, 3...current collector, 5...active material layer, 6...active material layer forming portion, 7...active material layer not formed portion, 11...electrode manufacturing system, 15...electrolyte treatment tank, 17, 19, 21...doping tank, 23A, 23B, 23C...cleaning tank, 25, 27, 29, 31, 33, 35, 37, 39, 40, 41, 43, 45, 46, 47, 49, 51, 52, 53, 55, 57, 58, 59, 61, 63, 64, 65, 67, 69, 70, 71, 73, 75, 77, 79, 81, 83, 85, 87, 89, 91, 93, 201, 203, 205, 2 07, 209, 211...conveyor roller, 101...supply roll, 103...take-up roll, 105...support stand, 107...circulation filtration unit, 109, 110, 111, 112, 113, 114...power source, 117...tub cleaner, 119...recovery unit, 121...end sensor, 131...upstream tank, 133...downstream tank, 137, 139, 141, 143...counter electrode unit, 149, 151...space, 153...conductive substrate, 155...alkali metal-containing plate, 157...porous insulating member, 161...filter, 163...pump, 165...piping, 213...blower DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Exemplary embodiments of the present disclosure will now be described with reference to the drawings. First Embodiment 1. Configuration of electrode 1 The structure of the electrode 1 will be described with reference to Figures 1 and 2. The electrode 1 has a strip-like shape. The electrode 1 includes a current collector 3 and an active material layer 5. The current collector 3 has a strip-like shape. The active material layers 5 are formed on both sides of the current collector 3.

[0015] The surface of the electrode 1 includes an active material layer formed portion 6 and an active material layer unformed portion 7. The active material layer formed portion 6 is a portion where an active material layer 5 is formed. The active material layer unformed portion 7 is a portion where an active material layer 5 is not formed. In the active material layer unformed portion 7, the current collector 3 is exposed.

[0016] The portion 7 without the active material layer formed has a band-like shape extending in the longitudinal direction L of the electrode 1. The portion 7 without the active material layer formed is located at an end of the electrode 1 in the width direction W of the electrode 1.

[0017] The current collector 3 is preferably a metal foil such as copper, nickel, or stainless steel. The current collector 3 may be a metal foil on which a conductive layer mainly made of a carbon material is formed. The thickness of the current collector 3 is, for example, 5 to 50 μm.

[0018] The active material layer 5 can be produced, for example, by applying a slurry containing an active material, a binder, and the like onto the current collector 3 and drying it.

[0019] Examples of the binder include rubber-based binders, fluorine-based resins, polypropylene, polyethylene, and fluorine-modified (meth)acrylic binders as disclosed in JP-A-2009-246137. Examples of the rubber-based binders include styrene-butadiene rubber (SBR) and NBR. Examples of the fluorine-based resins include polytetrafluoroethylene and polyvinylidene fluoride.

[0020] The slurry may contain other components in addition to the active material and the binder. Examples of the other components include a conductive agent and a thickener. Examples of the conductive agent include carbon black, graphite, vapor-grown carbon fiber, and metal powder. Examples of the thickener include carboxymethylcellulose, its Na salt or ammonium salt, methylcellulose, hydroxymethylcellulose, ethylcellulose, hydroxypropylcellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.

[0021] The thickness of the active material layer 5 is not particularly limited. The thickness of the active material layer 5 is, for example, 5 to 500 μm, preferably 10 to 200 μm, and particularly preferably 10 to 100 μm. The active material contained in the active material layer 5 is not particularly limited as long as it is an electrode active material applicable to a battery or capacitor that utilizes the insertion and desorption of alkali metal ions. The active material may be either a negative electrode active material or a positive electrode active material.

[0022] The negative electrode active material is not particularly limited. Examples of the negative electrode active material include carbon materials such as composite carbon materials, metals or semimetals such as Si and Sn that can be alloyed with lithium, or materials containing oxides thereof. Examples of the composite carbon material include graphite, easily graphitized carbon, difficultly graphitized carbon, and composite carbon materials in which graphite particles are coated with pitch or resin carbide. Specific examples of the carbon material include the carbon materials described in JP-A-2013-258392. Specific examples of the material containing metals or semimetals that can be alloyed with lithium, or oxides thereof, include materials described in JP-A-2005-123175 and JP-A-2006-107795.

[0023] Examples of the positive electrode active material include transition metal oxides and sulfur-based active materials. Examples of the transition metal oxides include cobalt oxide, nickel oxide, manganese oxide, and vanadium oxide. Examples of the sulfur-based active material include simple sulfur and metal sulfides. Both the positive electrode active material and the negative electrode active material may be made of a single material or may be made of a mixture of two or more materials.

[0024] The active material contained in the active material layer 5 is pre-doped with an alkali metal using an electrode production system 11 described below. The alkali metal pre-doped into the active material is preferably lithium or sodium, and particularly preferably lithium. When the electrode 1 is used for producing an electrode for a lithium ion secondary battery, the density of the active material layer 5 is preferably 1.30 to 2.00 g / cc, and particularly preferably 1.40 to 1.90 g / cc.

[0025] 2. Configuration of electrode manufacturing system 11 The configuration of the electrode manufacturing system 11 will be described with reference to Fig. 3 to Fig. 5. As shown in Fig. 3, the electrode manufacturing system 11 includes an electrolyte treatment tank 15, doping tanks 17, 19, and 21, cleaning tanks 23A, 23B, and 23C, and conveying rollers 25, 27, 29, 31, 33, 35, 37, 39, 40, 41, 43, 45, 46, 47, 49, 51, 52, 53, 55, 57, 58, 59, 61, 63, 64, 65, 67, 69, 70, 71, 73, 75, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 9, 81, 83, 85, 87, 89, 91, 93, 201, 203, 205, 207, 209, 211, a supply roll 101, a take-up roll 103, a support stand 105, a circulation filtration unit 107, six power sources 109, 110, 111, 112, 113, 114, a tub cleaner 117, a recovery unit 119, an end sensor 121, and a blower 213. Hereinafter, the above-mentioned multiple transport rollers may be collectively referred to as a transport roller group.

[0026] The electrolyte treatment tank 15 is a rectangular tank that is open at the top. The bottom surface of the electrolyte treatment tank 15 has a substantially U-shaped cross section. The electrolyte treatment tank 15 includes a partition plate 123. The partition plate 123 is supported by a support rod 125 that penetrates its upper end. The support rod 125 is fixed to a wall or the like (not shown). The partition plate 123 extends in the vertical direction, and divides the inside of the electrolyte treatment tank 15 into two spaces.

[0027] The transport roller 33 is attached to the lower end of the partition plate 123. The partition plate 123 and the transport roller 33 are supported by a support rod 127 that penetrates them. The vicinity of the lower end of the partition plate 123 is cut out so as not to come into contact with the transport roller 33. A space exists between the transport roller 33 and the bottom surface of the electrolyte treatment tank 15.

[0028] The configuration of the dope tank 17 will be described with reference to Fig. 4. The dope tank 17 is composed of an upstream tank 131 and a downstream tank 133. The upstream tank 131 is disposed on the side of the supply roll 101, and the downstream tank 133 is disposed on the side of the take-up roll 103. In the following description, the side of the supply roll 101 is referred to as the upstream side, and the side of the take-up roll 103 is referred to as the downstream side.

[0029] First, the configuration of the upstream tank 131 will be described. The upstream tank 131 is a rectangular tank that is open at the top. The bottom surface of the upstream tank 131 has a substantially U-shaped cross section. The upstream tank 131 includes a partition plate 135 and four counter electrode units 137, 139, 141, and 143.

[0030] The partition plate 135 is supported by a support rod 145 that passes through its upper end. The support rod 145 is fixed to a wall or the like (not shown). The partition plate 135 extends in the vertical direction and divides the interior of the upstream tank 131 into two spaces. The transport roller 40 is attached to the lower end of the partition plate 135. The partition plate 135 and the transport roller 40 are supported by a support rod 147 that passes through them. The partition plate 135 is cut out near its lower end so as not to come into contact with the transport roller 40. A space exists between the transport roller 40 and the bottom surface of the upstream tank 131.

[0031] The counter electrode unit 137 is disposed on the upstream side of the upstream tank 131. The counter electrode units 139 and 141 are disposed to sandwich the partition plate 135 from both sides. The counter electrode unit 143 is disposed on the downstream side of the upstream tank 131.

[0032] A space 149 exists between the counter electrode unit 137 and the counter electrode unit 139. A space 151 exists between the counter electrode unit 141 and the counter electrode unit 143. The counter electrode units 137, 139, 141, and 143 are connected to one pole of the power source 109.

[0033] The counter electrode units 137, 139, 141, and 143 may be connected to separate power sources. In this case, the counter electrode units 137, 139, 141, and 143 can be controlled individually. In addition, it becomes easier to electrically adjust the counter electrode units 137, 139, 141, and 143 according to the degree of doping of the electrode 1 in the doping process. As a result, it becomes easier to manufacture a desired doped electrode 1A. The doped electrode 1A is an electrode 1 including an active material layer 5 doped with an alkali metal.

[0034] The counter electrode units 137, 139, 141, and 143 have the same configuration. Here, the configuration of the counter electrode units 137 and 139 will be described with reference to FIG.

[0035] The counter electrode units 137 and 139 have a configuration in which a conductive base material 153, an alkali metal-containing plate 155, and a porous insulating member 157 are laminated. Examples of the material of the conductive base material 153 include copper, stainless steel, and nickel. The form of the alkali metal-containing plate 155 is not particularly limited, and examples of the form include an alkali metal plate and an alkali metal alloy plate. The thickness of the alkali metal-containing plate 155 is, for example, 0.03 to 6 mm.

[0036] The porous insulating member 157 has a plate-like shape. The porous insulating member 157 is layered on the alkali metal-containing plate 155. The plate-like shape of the porous insulating member 157 is the shape of the porous insulating member 157 when it is layered on the alkali metal-containing plate 155. The porous insulating member 157 may be a member that maintains a certain shape by itself, or may be a member that is easily deformable, such as a net.

[0037] The porous insulating member 157 is porous. Therefore, a doping solution, which will be described later, can pass through the porous insulating member 157. This allows the alkali metal-containing plate 155 to come into contact with the doping solution.

[0038] The porous insulating member 157 may be, for example, a mesh made of resin. Examples of resins include polyethylene, polypropylene, nylon, polyether ether ketone, and polytetrafluoroethylene. The mesh opening can be set appropriately. The mesh opening is, for example, 0.1 μm to 10 mm, and preferably 0.1 to 5 mm. The mesh thickness can be set appropriately. The mesh thickness is, for example, 1 μm to 10 mm, and preferably 30 μm to 1 mm. The mesh opening ratio can be set appropriately. The mesh opening ratio is, for example, 5 to 98%, preferably 5 to 95%, and more preferably 50 to 95%.

[0039] The porous insulating member 157 may be made entirely of an insulating material, or may include an insulating layer in part.

[0040] The downstream tank 133 basically has the same configuration as the upstream tank 131. However, inside the downstream tank 133, a transport roller 46 is present instead of the transport roller 40. In addition, the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 are connected to one pole of the power source 110.

[0041] The dope tank 19 basically has the same configuration as the dope tank 17. However, inside the dope tank 19, transport rollers 52 and 58 are present instead of transport rollers 40 and 46. Furthermore, the counter electrode units 137, 139, 141, and 143 of the upstream tank 131 of the dope tank 19 are connected to one pole of a power source 111. Furthermore, the counter electrode units 137, 139, 141, and 143 of the downstream tank 133 of the dope tank 19 are connected to one pole of a power source 112.

[0042] The dope tank 21 basically has the same configuration as the dope tank 17. However, inside the dope tank 21, transport rollers 64 and 70 are present instead of transport rollers 40 and 46. Furthermore, the counter electrode units 137, 139, 141, and 143 of the upstream tank 131 of the dope tank 21 are connected to one pole of the power source 113. Furthermore, the counter electrode units 137, 139, 141, and 143 of the downstream tank 133 of the dope tank 21 are connected to one pole of the power source 114.

[0043] Each of the cleaning tanks 23A, 23B, and 23C basically has the same configuration as the electrolytic solution treatment tank 15. However, inside the cleaning tanks 23A, 23B, and 23C, a transport roller 75 is present instead of the transport roller 33.

[0044] The dope solution carried out from the dope tank 21 adheres to the electrode 1 that has passed through the dope tank 21. In the cleaning tanks 23A, 23B, and 23C, the dope solution adhering to the electrode 1 is efficiently removed, which makes it easier to handle the electrode 1 in the next process.

[0045] The cleaning tanks 23A, 23B, and 23C contain, for example, the following cleaning liquid. The cleaning liquid is preferably an organic solvent, and preferably contains an aprotic solvent having a boiling point of 150° C. or less at 1 atm. Examples of the aprotic solvent having a boiling point of 150° C. or less at 1 atm include at least one selected from carbonate-based solvents, ester-based solvents, ether-based solvents, hydrocarbon-based solvents, ketone-based solvents, and nitrile-based solvents. Among these, carbonate-based solvents are preferred. As the carbonate-based solvent, at least one selected from dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, and ethyl methyl carbonate is particularly preferred. By using such a cleaning liquid, it becomes easier to remove the cleaning liquid from the electrode 1 after cleaning.

[0046] In addition, since the dope solution carried out from the dope tank 21 accumulates in the cleaning tanks 23A, 23B, and 23C, it is preferable to maintain the cleaning solution at a constant quality by adding or replacing the cleaning solution. A method for grasping the quality of the cleaning solution includes a method of installing sensors such as an insulation resistance meter and a conductivity meter in the cleaning tanks 23A, 23B, and 23C and periodically checking the values ​​measured by these sensors.

[0047] Among the group of conveying rollers, the conveying rollers 37, 39, 43, 45, 49, 51, 55, 57, 61, 63, 67, and 69 are made of a conductive material. The conveying rollers 37, 39, 43, 45, 49, 51, 55, 57, 61, 63, 67, and 69 correspond to conductive power supply rollers. Examples of conductive materials include stainless steel, gold, copper, and rhodium. Copper is particularly preferred as a conductive material. The conductive material may be a mixture of two or more materials. The presence of the conductive material, particularly on the surface of the power supply roller, makes it easier to suppress the reaction between the doped electrode 1A and the power supply roller. As a result, it is possible to mass-produce high-quality doped electrodes 1A.

[0048] The other conveying rollers in the conveying roller group are made of elastomer, except for the bearing portion. The conveying roller group conveys the electrode 1 along a fixed path. The conveying roller group conveys the electrode 1 along a cleaning path and a cleaning-omitted path. The cleaning path is a path from the supply roll 101, passing through the electrolyte treatment tank 15, the dope tank 17, the dope tank 19, the dope tank 21, at least one of the cleaning tanks 23A, 23B, and 23C, and the tub cleaner 117, to the take-up roll 103. In the cleaning path, the number of cleaning tanks through which the doped electrode 1A passes can be selected from 1 to 3.

[0049] The cleaning skip path is basically the same as the cleaning execution path, but after passing through the dope tank 21, the process proceeds to the tub cleaner 117 without passing through the cleaning tanks 23A, 23B, and 23C.

[0050] In addition, for both the cleaning execution path and the cleaning omission path, there are two types of paths after passing through the tub cleaner 117. In one path, after passing through the tub cleaner 117, the sheet is transported by transport rollers 201, 203, 205, 207, 209, and 211, and then transported by transport rollers 85, 87, 89, 91, and 93. This path will be referred to as the long drying path KL below.

[0051] The other path is a path in which the paper passes through tub cleaner 117, passes through transport rollers 201 and 203, and is transported by transport rollers 85, 87, 89, 91, and 93. This path is hereinafter referred to as a short drying path KS.

[0052] The portion of the path along which the electrode 1 is transported by the transport roller group that passes through the electrolyte treatment tank 15 is a path in which the electrode 1 first moves downward via transport rollers 29 and 31, and then the direction of movement is changed to upward by transport roller 33.

[0053] The portion of the path along which the conveying roller group conveys the electrode 1 passes through the dope tank 17 is as follows. First, the conveying roller 37 changes the direction of movement downward, so that the electrode 1 moves downward through the space 149 of the upstream tank 131. Next, the conveying roller 40 changes the direction of movement upward, so that the electrode 1 moves upward through the space 151 of the upstream tank 131. Next, the conveying rollers 41 and 43 change the direction of movement downward, so that the electrode 1 moves downward through the space 149 of the downstream tank 133. Next, the conveying roller 46 changes the direction of movement upward, so that the electrode 1 moves upward through the space 151 of the downstream tank 133. Finally, the conveying roller 47 changes the direction of movement horizontally, so that the electrode 1 moves toward the dope tank 19.

[0054] The portion of the path along which the conveying roller group conveys the electrode 1 passes through the dope tank 19 is as follows. First, the conveying roller 49 changes the direction of movement downward, so that the electrode 1 moves downward through the space 149 of the upstream tank 131. Next, the conveying roller 52 changes the direction of movement upward, so that the electrode 1 moves upward through the space 151 of the upstream tank 131. Next, the conveying rollers 53 and 55 change the direction of movement downward, so that the electrode 1 moves downward through the space 149 of the downstream tank 133. Next, the conveying roller 58 changes the direction of movement upward, so that the electrode 1 moves upward through the space 151 of the downstream tank 133. Finally, the conveying roller 59 changes the direction of movement horizontally, so that the electrode 1 moves toward the dope tank 21.

[0055] The portion of the path along which the group of transport rollers transports the electrode 1 passes through the dope tank 21 is as follows. First, the direction of movement is changed downward by the transport roller 61, and the electrode 1 moves downward through the space 149 of the upstream tank 131. Next, the direction of movement is changed upward by the transport roller 64, and the electrode 1 moves upward through the space 151 of the upstream tank 131. Next, the direction of movement is changed downward by the transport rollers 65 and 67, and the electrode 1 moves downward through the space 149 of the downstream tank 133. Next, the direction of movement is changed upward by the transport roller 70, and the electrode 1 moves upward through the space 151 of the downstream tank 133. Finally, the direction of movement is changed horizontally by the transport roller 71, and the electrode 1 moves toward the cleaning tank 23.

[0056] In addition, the portion of the cleaning path that passes through cleaning tanks 23A, 23B, and 23C is a path in which the direction of movement is first changed downward by conveying roller 73 and moves downward, and then the direction of movement is changed upward by conveying roller 75.

[0057] The electrode 1 is wound around the supply roll 101. That is, the supply roll 101 holds the electrode 1 in a wound state. The active material in the electrode 1 held by the supply roll 101 has not yet been doped with an alkali metal.

[0058] The group of transport rollers pulls out and transports the electrode 1 held by the supply roll 101. The winding roll 103 winds up and stores the electrode 1 transported by the group of transport rollers. When the electrode 1 is transported along a path passing through the doping tanks 17, 19, and 21, the active material layer 5 is doped with an alkali metal. The method of doping the alkali metal is a method of electrically doping the active material with the alkali metal using counter electrode units 139, 141, and 143 provided opposite the electrode 1 in the doping tanks 17, 19, and 21. By doping the active material layer 5 with the alkali metal, the electrode 1 becomes a doped electrode 1A including an active material layer 5 doped with the alkali metal. The electrode 1 stored on the winding roll 103 is a doped electrode 1A.

[0059] The support stand 105 supports the electrolyte treatment tank 15, the dope tanks 17, 19, 21, and the cleaning tanks 23A, 23B, 23C from below. The height of the support stand 105 can be changed. The circulation filtration units 107 are provided in the dope tanks 17, 19, 21, respectively. The circulation filtration units 107 include a filter 161, a pump 163, and a pipe 165.

[0060] In the circulation filtration unit 107 provided in the dope tank 17, the pipe 165 is a circulation pipe that goes out from the dope tank 17, passes through the pump 163 and the filter 161 in order, and returns to the dope tank 17. The dope solution in the dope tank 17 circulates through the pipe 165 and the filter 161 by the driving force of the pump 163, and returns to the dope tank 17 again. At this time, foreign matter in the dope solution is filtered by the filter 161. Examples of the foreign matter include foreign matter precipitated from the dope solution and foreign matter generated from the electrode 1. The material of the filter 161 is, for example, a resin such as polypropylene or polytetrafluoroethylene. The pore size of the filter 161 can be appropriately set. The pore size of the filter 161 is, for example, 0.2 μm to 50 μm.

[0061] The circulation filtration units 107 provided in the dope tanks 19 and 21 have the same configuration and provide the same effects. For convenience, the dope solution is not shown in FIGS.

[0062] One terminal of the power source 109 is connected to the transport rollers 37 and 39. The other terminal of the power source 109 is connected to the counter electrode units 137, 139, 141, and 143 provided in the upstream tank 131 of the dope tank 17. The electrode 1 contacts the transport rollers 37 and 39. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the dope solution, which is an electrolyte. Therefore, in the upstream tank 131 of the dope tank 17, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolyte.

[0063] One terminal of the power source 110 is connected to the transport rollers 43 and 45. The other terminal of the power source 110 is connected to the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 of the dope tank 17. The electrode 1 contacts the transport rollers 43 and 45. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the dope solution, which is an electrolyte. Therefore, in the downstream tank 133 of the dope tank 17, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolyte.

[0064] One terminal of the power source 111 is connected to the transport rollers 49 and 51. The other terminal of the power source 111 is connected to the counter electrode units 137, 139, 141, and 143 provided in the upstream tank 131 of the dope tank 19. The electrode 1 contacts the transport rollers 49 and 51. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the dope solution, which is an electrolyte. Therefore, in the upstream tank 131 of the dope tank 19, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolyte.

[0065] One terminal of the power source 112 is connected to the transport rollers 55 and 57. The other terminal of the power source 112 is connected to the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 of the dope tank 19. The electrode 1 contacts the transport rollers 55 and 57. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the dope solution, which is an electrolyte. Therefore, in the downstream tank 133 of the dope tank 19, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolyte.

[0066] One terminal of the power source 113 is connected to the transport rollers 61 and 63. The other terminal of the power source 113 is connected to the counter electrode units 137, 139, 141, and 143 provided in the upstream tank 131 of the dope tank 21. The electrode 1 contacts the transport rollers 61 and 63. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the dope solution, which is an electrolyte. Therefore, in the upstream tank 131 of the dope tank 21, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolyte.

[0067] One terminal of the power source 114 is connected to the transport rollers 67 and 69. The other terminal of the power source 114 is connected to the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 of the dope tank 21. The electrode 1 contacts the transport rollers 67 and 69. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the dope solution, which is an electrolyte. Therefore, in the downstream tank 133 of the dope tank 21, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolyte.

[0068] The tub cleaner 117 cleans the portion 7 of the doped electrode 1A where the active material layer is not formed. If residual organic components derived from the doping solution or the like remain in the portion 7 of the doped electrode 1A where the active material layer is not formed, welding defects are likely to occur when the portion 7 of the doped electrode 1A where the active material layer is not formed is welded.

[0069] After cleaning with the tub cleaner 117, the amount of remaining organic components on the portion 7 where the active material layer is not formed can be measured. For example, a total reflection measurement method using a Fourier transform infrared spectrophotometer can be used as the measurement method. The characteristic peak of the remaining organic components is at a wave number of 1180 cm. -1 ~1250cm -1 Therefore, the amount of remaining organic components can be measured based on the absorbance peak area value in this range.

[0070] After cleaning with the tub cleaner 117, the quality of the doped electrode 1A can be evaluated based on the amount of organic components remaining on the active material layer unformed portion 7. For example, -1 ~1250cm -1 The quality of doped electrode 1A can be evaluated based on whether the absorbance peak area value is 0.1 or less in this range. If the absorbance peak area value is 0.1 or less, it can be determined that active material layer unformed portion 7 has been sufficiently cleaned.

[0071] The recovery units 119 are disposed in the electrolyte treatment tank 15, the dope tanks 17, 19, 21, and the cleaning tanks 23A, 23B, 23C, respectively. The recovery units 119 recover the liquid taken out of the tanks by the electrode 1 and return it to the tanks.

[0072] The end sensor 121 detects the position of the end of the electrode 1 in the width direction W. An end position adjustment unit (not shown) adjusts the positions of the supply roll 101 and the take-up roll 103 in the width direction W based on the detection result of the end sensor 121.

[0073] There are multiple blowers 213. The multiple blowers 213 are lined up along the path along which the doped electrode 1A is transported. Some of the blowers 213 blow gas onto the doped electrode 1A being transported, regardless of whether the path of the doped electrode 1A is the long drying path KL or the short drying path KS. Other blowers 213 blow gas onto the doped electrode 1A being transported along the long drying path KL. Therefore, when the path of the doped electrode 1A is the long drying path KL, the doped electrode 1A is blown with gas for a longer period of time than when the path is the short drying path KS.

[0074] The gas blown by the blower 213 is preferably a gas inert to the active material doped with an alkali metal. Examples of such gas include helium gas, neon gas, argon gas, nitrogen gas, and dehumidified air from which moisture has been removed. The gas may be a gas consisting of a single component, or a mixed gas consisting of two or more components.

[0075] When the cleaning omission path is selected and the doped electrode 1A passes through the tub cleaner 117, the doped solution adheres to the surface of the doped electrode 1A. The blower 213 blows gas onto the doped electrode 1A, causing the solvent of the doped solution to evaporate. Components of the doped solution remain on the surface of the doped electrode 1A. These remaining components are hereinafter referred to as residual components. The residual components are residues of one or more components contained in the doped solution that adhere to the doped electrode 1A. Most of the residual components can be removed from the doped electrode 1A by cleaning the doped electrode 1A. Therefore, the mass of the residual components is approximately equal to the mass of the solvent basis weight a described below.

[0076] 3. Composition of the dope solution When the electrode manufacturing system 11 is used, a dope solution is contained in the electrolyte treatment tank 15 and the dope tanks 17, 19, and 21. The dope solution contains alkali metal ions and a solvent. The dope solution is an electrolyte.

[0077] Examples of the solvent include organic solvents. Examples of the organic solvent include aprotic organic solvents. Examples of the aprotic organic solvent include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, dipropyl carbonate, γ-butyrolactone, sulfolane, diethylene glycol dimethyl ether (diglyme), diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether (triglyme), triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether (tetraglyme).

[0078] When the solvent is the above-mentioned aprotic organic solvent, it is possible to efficiently dope the electrode 1. In addition, by using the doped electrode 1A that has been doped using the above-mentioned aprotic organic solvent, a secondary battery with high battery stability can be obtained.

[0079] As the aprotic organic solvent, an organic solvent belonging to a specific group is preferred.As the organic solvent belonging to a specific group, for example, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, and propylene carbonate are preferred.Among the organic solvents belonging to such a specific group, dimethyl carbonate, ethylene carbonate, and methyl ethyl carbonate are more preferred, and it is particularly preferred to use at least dimethyl carbonate and ethylene carbonate in combination.

[0080] When at least dimethyl carbonate and ethylene carbonate are used in combination as the organic solvent belonging to the specific group, the volume ratio of dimethyl carbonate in the organic solvent is preferably 30% or more, more preferably 50% or more, and particularly preferably 70% or more. By using the doped electrode 1A doped with the organic solvent having such a composition, a secondary battery with high battery stability can be obtained.

[0081] When the solvent is an organic solvent belonging to a specific group, it is possible to particularly efficiently dope the electrode 1. Furthermore, by using a doped electrode 1A that has been doped with an organic solvent belonging to a specific group, a secondary battery with particularly high battery stability can be obtained.

[0082] In addition, as the organic solvent, for example, an ionic liquid such as a quaternary imidazolium salt, a quaternary pyridinium salt, a quaternary pyrrolidinium salt, a quaternary piperidinium salt, etc. The organic solvent may be composed of a single component, or may be a mixed solvent of two or more components.

[0083] The alkali metal ions contained in the dope solution are ions constituting an alkali metal salt. The alkali metal salt is preferably a lithium salt or a sodium salt. The anion moiety constituting the alkali metal salt is, for example, PF6 - , PF3(C2F5)3 -, PF3(CF3)3 - Phosphorus anion with fluoro group such as BF4 - , BF2(CF)2 - , BF3(CF3) - , B(CN)4 - Boron anions with fluoro or cyano groups such as N(FSO2)2 - , N(CF3SO2)2 - , N(C2F5SO2)2 - Sulfonylimide anions with fluoro groups such as CF3SO3 - and the like.

[0084] The concentration of the alkali metal salt in the doping solution is preferably 0.1 mol / L or more, and more preferably in the range of 0.5 to 1.5 mol / L. When the concentration of the alkali metal salt is within this range, pre-doping of the alkali metal proceeds efficiently.

[0085] The dope solution may further contain additives such as vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, 1-(trifluoromethyl)ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, diethyl sulfone, etc. The amount of such additives added is preferably 5% by mass or less, more preferably 3% by mass or less, based on the mass ratio of the dope solution.

[0086] The dope solution may further contain a flame retardant such as a phosphazene compound. The amount of the flame retardant added is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the dope solution, from the viewpoint of effectively controlling the thermal runaway reaction when doping with an alkali metal. Also, the amount of the flame retardant added is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the dope solution, from the viewpoint of obtaining a high-quality doped electrode 1A.

[0087] 4. Method for manufacturing doped electrode 1A using electrode manufacturing system 11 The manufacturing method of the doped electrode 1A is as follows. The electrode 1 before pre-doping is wound around the supply roll 101. Next, the electrode 1 before pre-doping is pulled out from the supply roll 101 and sent to the take-up roll 103 along the above-mentioned path. Next, the electrolyte treatment tank 15, the doping tanks 17, 19, 21, and the cleaning tanks 23A, 23B, 23C are raised and set in the fixed positions shown in FIG.

[0088] Next, the dope solution is placed in the electrolyte treatment tank 15 and the dope tanks 17, 19, and 21. The dope solution is the dope solution described in "3. Composition of the dope solution." When the cleaning execution path is selected as the transport path, cleaning liquid is placed in the cleaning tanks 23A, 23B, and 23C.

[0089] Next, the electrode 1 is transported along the above-mentioned path from the supply roll 101 to the take-up roll 103 by a group of transport rollers. The path along which the electrode 1 is transported passes through the doping tanks 17, 19, and 21. When the electrode 1 passes through the doping tanks 17, 19, and 21, the active material contained in the active material layer 5 is pre-doped with an alkali metal.

[0090] Furthermore, when the cleaning execution path is selected as the transport path, the transport roller group transports the electrode 1 to one or more of the cleaning tanks 23A, 23B, and 23C. The electrode 1 is cleaned in one or more of the cleaning tanks 23A, 23B, and 23C while being transported by the transport roller group.

[0091] Furthermore, the group of transport rollers continuously transports the electrode 1 to a tub cleaner 117. The portion of the electrode 1 transported to the tub cleaner 117 has already been subjected to pre-doping processing and has become a doped electrode 1A. The tub cleaner 117 cleans a portion 7 of the doped electrode 1A where an active material layer is not formed.

[0092] The doped electrode 1A may be a positive electrode or a negative electrode. When manufacturing a positive electrode, the electrode manufacturing system 11 dopes a positive electrode active material with an alkali metal. When manufacturing a negative electrode, the electrode manufacturing system 11 dopes a negative electrode active material with an alkali metal.

[0093] When lithium is absorbed in the negative electrode active material of a lithium ion capacitor, the doping amount of the alkali metal is preferably 70 to 95% of the theoretical capacity of the negative electrode active material.When lithium is absorbed in the negative electrode active material of a lithium ion secondary battery, the doping amount of the alkali metal is preferably 10 to 30% of the theoretical capacity of the negative electrode active material.

[0094] 5. Manufacturing method of secondary battery An example of the secondary battery is a lithium ion secondary battery. The secondary battery includes an electrode cell. The electrode cell has a configuration in which a negative electrode and a positive electrode are stacked. In the secondary battery, for example, the negative electrode is manufactured by the above-mentioned "4. Manufacturing method of doped electrode 1A using electrode manufacturing system 11". Next, the negative electrode and the positive electrode are stacked to form an electrode cell.

[0095] 6. Effects of the method for manufacturing doped electrode and the method for manufacturing secondary battery (6-1) When the cleaning-free route is selected as the transport route for the electrode 1, the doped electrode 1A having the dope solution attached thereto can be dried on the long drying route KL or the short drying route KS. Drying means removing the solvent of the dope solution. The doped electrode 1A after drying contains 5 parts by mass or more and 40 parts by mass or less of residual components per 100 parts by mass of the active material layer 5. By using the doped electrode 1A containing the residual components, a secondary battery with high battery stability can be manufactured.

[0096] The doped electrode 1A after drying preferably contains 10 parts by mass or more and 30 parts by mass or less of residual components per 100 parts by mass of active material layer 5, more preferably contains 15 parts by mass or more and 25 parts by mass or less of residual components per 100 parts by mass of active material layer 5, and particularly preferably contains 15 parts by mass or more and 20 parts by mass or less of residual components.

[0097] A secondary battery with even higher battery stability can be manufactured when the doped electrode 1A after drying contains 10 parts by mass or more and 30 parts by mass or less of the residual component per 100 parts by mass of the active material layer 5. A secondary battery with especially high battery stability can be manufactured when the doped electrode 1A after drying contains 15 parts by mass or more and 25 parts by mass or less of the residual component per 100 parts by mass of the active material layer 5.

[0098] (6-2) When the cleaning-free path is selected as the transport path for the electrode 1, the process of cleaning the doped electrode 1A is not required, and therefore the productivity of the doped electrode 1A is high.

[0099] Furthermore, even if a cleaning execution path is selected as the transport path for the electrode 1, if any of the cleaning tanks 23A, 23B, and 23C is not used, the productivity of the doped electrode 1A is higher than when all of the cleaning tanks 23A, 23B, and 23C are used.

[0100] (6-3) The doped electrode 1A containing the residual components can be manufactured by an electrode manufacturing system that does not include a cleaning mechanism such as the cleaning tanks 23A, 23B, and 23C. Therefore, the electrode manufacturing system can be made smaller.

[0101] 7. Working Example Example 1 (i) Preparation of Electrode 1 A long strip-shaped current collector 3 was prepared. The current collector 3 was a negative electrode current collector. The size of the current collector 3 was 130 mm wide, 100 mm long, and 8 μm thick. The surface roughness Ra of the current collector 3 was 0.1 μm. The current collector 3 was made of copper foil. An active material layer 5 was formed on each of both sides of the current collector 3. The active material layer 5 was a negative electrode active material layer.

[0102] The coating amount of the active material layer 5 is 100 g / m 2As shown in FIG. 1, the active material layer 5 was formed along the longitudinal direction of the current collector 3. The active material layer 5 was formed over a width of 120 mm from one end of the current collector 3 in the width direction W. The width of the portion 7 where the active material layer was not formed at the other end of the current collector 3 in the width direction W was 10 mm. The portion 7 where the active material layer was not formed is a portion where the active material layer 5 was not formed. Thereafter, the electrode 1 was obtained by drying and pressing.

[0103] The active material layer 5 contained a negative electrode active material, carboxymethyl cellulose, acetylene black, a binder, and a dispersant in a mass ratio of 88:3:5:3:1. The negative electrode active material was a mixture of a Si-based active material and a graphite-based active material. The negative electrode active material contained a Si-based active material and a graphite-based active material in a mass ratio of 2:8. The acetylene black corresponds to a conductive agent.

[0104] (ii) Fabrication of counter electrode units 137, 139, 141, and 143 A polypropylene (PP) resin film was attached onto a copper plate. The copper plate had a length of 1000 mm, a width of 220 mm, and a thickness of 3 mm. The resin film had a length of 810 mm, a width of 120 mm, and a thickness of 470 μm. The resin film had a mesh shape with multiple openings. The opening ratio of the resin film was 50%.

[0105] Furthermore, Li foil was attached onto the resin film. The length and width of the Li foil were the same as the length and width of the resin film. The thickness of the Li foil was 2 mm. The resin film and Li foil were pressed onto a copper plate using a roll press device to obtain counter electrode units 137, 139, 141, and 143. The linear pressure during pressing was 5 kgf / cm. The copper plate corresponds to the conductive substrate 153. The Li foil corresponds to the alkali metal-containing plate 155.

[0106] (iii) Fabrication of doped electrode 1A The electrode manufacturing system 11 shown in FIG. 3 was prepared, and the electrode 1 was passed through it. In addition, the counter electrode units 137, 139, 141, and 143 were installed in the dope tanks 17, 19, and 21, respectively. Next, the dope solution was supplied into the dope tanks 17, 19, and 21. The dope solution was a solution containing 1.2M LiPF6. The solvent of the dope solution was a mixed solution containing EC (ethylene carbonate) and DMC (dimethyl carbonate) at a volume ratio of 3:7. The composition of the dope solution 1 in Example 1 is D1. The dope tanks 17, 19, and 21 were in a state of containing the dope solution and the counter electrode units 137, 139, 141, and 143. The transport path of the electrode 1 was a cleaning-omitted path and a short drying path KS.

[0107] Next, the electrode 1 and the counter electrode units 137, 139, 141, and 143 fed through the electrode manufacturing system 11 were connected to a DC power supply equipped with a current and voltage monitor. While the electrode 1 was transported at a speed of 1.24 m / min, a current of 154 A was applied to the entire electrode manufacturing system 11. At this time, the pre-doping current density per unit area of ​​the electrode 1 was 10 mA / cm. 2 It was. At this time, the center in the width direction W of the active material layer 5 of the electrode 1 coincided with the center in the width direction W of the Li foil of the counter electrode units 137, 139, 141, and 143. At this time, even if the pre-doping was continued, the voltage did not continue to rise. Pre-doping could be performed with the voltage stable at 3.0V.

[0108] After passing through the doping tank 21, the doped electrode 1A proceeded to the tub cleaner 117 without passing through the cleaning tanks 23A, 23B, and 23C. After passing through the tub cleaner 117, the doped electrode 1A proceeded to the short drying path KS. When the doped electrode 1A entered the short drying path KS, the doped electrode 1A had a doped solution attached to its surface. In the short drying path KS, the doped electrode 1A was dried by being blown with gas from the blower 213. The gas blown by the blower 213 was nitrogen. The flow rate of each blower 213 was 5 L / min. The total number of blowers 213 was 18. In Example 1, the number of blowers 213 that blew gas to the doped electrode 1A was 6.

[0109] (iv) Calculation of mass ratio X For the obtained doped electrode 1A, the mass ratio X was calculated. The mass ratio X (%) is a value calculated by the following formula 1. (Formula 1) X=(a / b)×100 a is the weight per unit of the solvent. The unit of the weight per unit of the solvent is g / cm 2 b is the active material layer area density. The unit of the active material layer area density b is g / cm 2 It is.

[0110] The solvent weight a is calculated as follows. A sample with a diameter of 16 mm was punched out from the doped electrode 1A using a hand punch manufactured by Nogami Giken. The initial mass wa1 of the sample was measured using an electronic balance. Next, the sample was thoroughly washed using DMC solvent and dried. The mass wa2 of the sample after drying was measured using an electronic balance. The units of wa1 and wa2 are both g. The solvent weight a was calculated using the following formula 2. (Equation 2) a = (wa1-wa2) / S S is the area of ​​the sample with a diameter of 16 mm. S is measured in cm 2 It is.

[0111] The active material layer weight b is calculated by the following formula 3. (Equation 3) b = (wa2-wa3) / S wa3 is the mass of a sample having a diameter of 16 mm punched out from the current collector 3. The unit of wa3 is g.

[0112] The mass ratio X in the doped electrode 1A was 17%, as shown in Table 1. As described above, the mass of the residual component was approximately equal to the mass of the solvent basis weight a. Therefore, the mass ratio X represents the ratio of the mass of the residual component to the mass of the active material layer 5. That is, the obtained doped electrode 1A contains the components of the dope solution in parts by mass corresponding to the mass ratio X per 100 parts by mass of the active material layer 5.

[0113] [Table 1] In addition, "Yes (short)" in the "Drying process" row of Table 1 means that the doped electrode 1A passed through the short drying path KS. Also, "Yes (long)" means that the doped electrode 1A passed through the long drying path KL. Also, "No" means that the doped electrode 1A did not pass through either the long drying path KL or the short drying process KS. The fewer the number of cleaning tanks that the doped electrode 1A passes through, the larger the mass ratio X. When the doped electrode 1A passes through the short drying path KS, the mass ratio X is larger than when it passes through the long drying path KL.

[0114] (v) Battery stability evaluation The battery stability of the doped electrode 1A was evaluated by the following method. A part of the doped electrode 1A was punched out using a Thomson blade manufactured by Takahashi Katasei Co., Ltd. The punched out part was used as the negative electrode. The basic shape of the negative electrode was a rectangle with a length of 2.6 cm and a width of 4.0 cm. The negative electrode had a terminal weld protruding from one side of the rectangle to the outer periphery. The negative electrode was exposed to an environment with a dew point of -45°C in a glove box for 5 hours.

[0115] Next, the negative electrode was brought into a dry room with a dew point of -60° C. In the dry room, a first evaluation half-cell was fabricated using the negative electrode. The first evaluation half-cell was fabricated as follows.

[0116] A separator, a counter electrode, and a separator were laminated in this order on one side of the negative electrode. A separator, a counter electrode, and a separator were laminated in this order on the opposite side of the negative electrode. As a result, a laminate was obtained. The separator was made of a polyethylene nonwoven fabric having a thickness of 35 μm. The counter electrode was a copper lath foil with metallic lithium attached. The basic shape of the copper lath foil was a rectangle with a length of 2.6 cm and a width of 3.9 cm. The copper lath foil had a terminal welding portion protruding from one side of the rectangle toward the outer periphery.

[0117] Next, the four sides of the laminate were taped. Next, the negative electrode terminal weld and the counter electrode terminal weld were ultrasonically welded to a copper terminal. The terminal size was 5 mm wide, 50 mm long, and 0.2 mm thick.

[0118] Next, the laminate was sandwiched between two laminate films. The shape of the laminate film was rectangular. The size of the laminate film was 6.5 cm long and 8.0 cm wide. Three of the four sides of the two laminate films were fused together. As a result, the two laminate films became a bag with only one side open. The laminate was contained in the bag.

[0119] Next, the laminate in the bag was vacuum-impregnated with an electrolyte. The electrolyte was a solution containing 1.2 M LiPF6. The solvent for the electrolyte was a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 3:7.

[0120] Next, one of the four sides of the bag that had not yet been fused was fused. The above steps completed the first evaluation half-cell. The second evaluation half-cell was basically produced in the same manner as the first evaluation half-cell. However, the second evaluation half-cell was produced using a negative electrode that had not been exposed to dry air with a dew point of -45°C.

[0121] The first evaluation half-cell and the second evaluation half-cell correspond to secondary batteries. A method for fabricating the first evaluation half-cell and the second evaluation half-cell corresponds to a method for fabricating secondary batteries.

[0122] The first evaluation half-cell and the second evaluation half-cell were placed in a thermostatic chamber at 25° C. Next, the initial charge-discharge efficiency E, represented by the following formula (4), was calculated for each of the first evaluation half-cell and the second evaluation half-cell. The unit of the initial charge-discharge efficiency E is %. (Formula 4) E=(C1 / C2)×100 C1 is the initial discharge capacity. C2 is the initial charge capacity. The units of C1 and C2 are mAh / cm 2 The initial discharge capacity C1 is the capacity when the cell is charged at a constant current of 10 mA until the cell voltage becomes 0.01 V, and then the charging is continued until the current value drops to 1 mA while applying a constant voltage of 0.01 V. The initial charge capacity C2 is the capacity when the cell is discharged at a constant current of 10 mA until the cell voltage becomes 2.0 V after measuring the initial discharge capacity C1.

[0123] The first evaluation half-cell had an initial charge-discharge efficiency E of 99%, and the second evaluation half-cell had an initial charge-discharge efficiency E of 100%.

[0124] Based on the value of the initial charge-discharge efficiency E in the first evaluation half-cell, the battery stability was evaluated according to the following criteria. The evaluation results are shown in Table 1 above. (Battery stability evaluation criteria) A: The initial charge / discharge efficiency is 98.5% or higher.

[0125] B: The initial charge / discharge efficiency is less than 98.5% and greater than or equal to 95.5%.

[0126] C: The initial charge / discharge efficiency is less than 95.5%.

[0127] (vi) Productivity assessment The time from when the electrode 1 starts to be pulled out from the supply roll 101 to when the doped electrode 1A is wound around the winding roll 103 is defined as a working time T. The working time ratio TR was calculated by the following formula 5. The working time ratio TR is expressed in %. (Formula 5) TR=(T / T r1 ) x 100 T r1 is the work time T in Comparative Example 1 described later. Based on the value of the work time ratio TR, the productivity was evaluated according to the following criteria. The evaluation results are shown in Table 1 above. (Productivity Evaluation Criteria) A: The working time ratio TR is less than 70%. B: The work time ratio TR is between 70% and 80%. Example 2 A doped electrode 1A was manufactured and evaluated in a manner similar to that of Example 1. However, the electrode 1 was transported along the cleaning execution path. The doped electrode 1A passed through the cleaning tank 23A but did not pass through the cleaning tanks 23B and 23C.

[0128] In Example 2, the mass ratio X was 12%. The initial charge-discharge efficiency E of the first evaluation half-cell was 98%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as A. Example 3 Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the transport path of the electrode 1 was the cleaning execution path. The doped electrode 1A passed through the cleaning tank 23A, but did not pass through the cleaning tanks 23B and 23C. The transport path of the electrode 1 was the long drying path KL. The number of blowers 213 that blew gas onto the doped electrode 1A was 18.

[0129] In Example 3, the mass ratio X was 8%. The initial charge-discharge efficiency E of the first evaluation half-cell was 97%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as B. Example 4 A doped electrode 1A was produced and evaluated basically in the same manner as in Example 1. However, the flow rate of the blowers 213 was 2.5 L / min per blower.

[0130] In Example 4, the mass ratio X was 27%. The initial charge-discharge efficiency E of the first evaluation half-cell was 98%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as A. Example 5 Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the composition of the doping solution supplied to the doping tanks 17, 19, and 21 is different. The doping solution in Example 5 is a solution containing 1.2M LiPF6. The solvent of the doping solution is a mixed solution containing EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate) in a volume ratio of 1:1:1. The composition of the doping solution in Example 5 is D2.

[0131] In Example 5, the mass ratio X was 21%. The initial charge-discharge efficiency E of the first evaluation half-cell was 98%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as A. Example 6 Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the composition of the doping solution supplied to the doping tanks 17, 19, and 21 is different. The doping solution in Example 6 is a solution containing 1.4M LiPF6. The solvent of the doping solution is a mixed solution containing EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 3:7, and further containing 1 mass% FEC (fluoroethylene carbonate) in a mass ratio. The composition of the doping solution in Example 6 is D3.

[0132] In Example 6, the mass ratio X was 22%. The initial charge-discharge efficiency E of the first evaluation half-cell was 99%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as A. Example 7 Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the composition of the doping solution supplied to the doping tanks 17, 19, and 21 is different. The doping solution in Example 7 is a solution containing 1.2M LiPF6. The solvent of the doping solution is a mixed solution containing EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 3:7, and further containing 5 mass% of FEC (fluoroethylene carbonate) in a mass ratio. The composition of the doping solution in Example 7 is D4.

[0133] In Example 7, the mass ratio X was 17%. The initial charge-discharge efficiency E of the first evaluation half-cell was 99%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as A. Comparative Example 1 A doped electrode 1A was manufactured and evaluated basically in the same manner as in Example 1. However, the electrode 1 was transported along the cleaning execution path. The doped electrode 1A passed through cleaning tanks 23A, 23B, and 23C.

[0134] In Comparative Example 1, the mass ratio X was 3%. The initial charge-discharge efficiency E of the first evaluation half-cell was 95%. The initial charge-discharge efficiency E of the second evaluation half-cell was 100%. The productivity was evaluated as C. Comparative Example 2 The doped electrode 1A was produced basically in the same manner as in Example 1. However, the doped electrode 1A did not pass through either the long drying route KL or the short drying route KS, and therefore the blower 213 did not blow gas onto the doped electrode 1A.

[0135] The precipitate of the dope solution was accumulated on the transport rollers after the dope tank 17, and the electrode 1 was broken. Therefore, evaluation could not be performed. <Other embodiments> Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0136] (1) The function of one component in each of the above embodiments may be shared by multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of each of the above embodiments may be omitted. Also, at least part of the configuration of each of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0137] (2) In addition to the above-described method for manufacturing a doped electrode and method for manufacturing a secondary battery, the present disclosure can also be realized in various forms, such as a doped electrode, a secondary battery, and an electrode manufacturing system.

Claims

1. A method for producing a secondary battery using a doped electrode including an active material layer doped with an alkali metal, comprising: a doping solution containing ions of the alkali metal and an aprotic organic solvent, and an electrode containing an active material layer is transported along a path passing through a doping tank containing a counter electrode unit, thereby producing the doped electrode; The doped electrode taken out of the doping tank is dried without contacting the doped electrode with a cleaning solution capable of removing the doped solution so that the doped electrode contains 5 parts by mass or more and 40 parts by mass or less of the components of the doped solution relative to 100 parts by mass of the active material layer; The method for producing a secondary battery includes manufacturing the secondary battery using the doped electrode after drying.

2. A method for producing a doped electrode including an active material layer doped with an alkali metal, comprising: a doping solution containing ions of the alkali metal and an aprotic organic solvent, and an electrode containing an active material layer is transported along a path passing through a doping tank containing a counter electrode unit, thereby producing the doped electrode; The doped electrode taken out of the doping tank is dried without contacting the doped electrode with a cleaning solution capable of removing the doped solution so that the doped electrode contains 5 parts by mass or more and 40 parts by mass or less of the components of the doped solution relative to 100 parts by mass of the active material layer. Method for producing doped electrodes.

3. A method for producing a doped electrode according to claim 2, comprising the steps of: the alkali metal is electrically doped into the active material layer using the counter electrode unit provided opposite the electrode in the doping tank; Method for manufacturing doped electrodes.

4. A method for producing a doped electrode according to claim 2 or 3, comprising the steps of: Drying the doped electrode that has been removed from the doping tank by spraying at least one gas selected from the group consisting of helium gas, neon gas, argon gas, and nitrogen gas onto the doped electrode; Method for producing doped electrodes.

5. A method for producing a doped electrode according to any one of claims 2 to 4, comprising the steps of: The aprotic organic solvent is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, dipropyl carbonate, γ-butyrolactone, sulfolane, diethylene glycol dimethyl ether (diglyme), diethylene glycol methyl ethyl ether, triethylene glycol dimethyl ether (triglyme), triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether (tetraglyme). Method for producing doped electrodes.

6. A method for producing a doped electrode according to any one of claims 2 to 4, comprising the steps of: The aprotic organic solvent is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, and propylene carbonate. Method for producing doped electrodes.

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