Method for manufacturing a doped electrode

Abstract

To provide a method for manufacturing a doped electrode that can restrain generation of by-products in a dope solution during pre-doping.SOLUTION: A method for manufacturing a doped electrode including an active material layer doped with an alkali metal is provided. The method conveys a strip-shaped electrode containing an active material layer along a path passing through a dope tank accommodating a dope solution containing alkali metal ions and an aprotic organic solvent, and a counter electrode unit, and electrically connecting the counter electrode unit and the strip-shaped electrode containing the active material layer through the dope solution, and the content ratio of dimethyl carbonate in the aprotic organic solvent is equal to 40 vol% or more and 95 vol% or less.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a doped electrode.

Background Art

[0002] In recent years, the miniaturization and weight reduction of electronic devices have been remarkable. Along with this, the demand for miniaturization and weight reduction of batteries used as driving power sources for such electronic devices has been increasing even more.

[0003] In order to meet such requirements for miniaturization and weight reduction, non-aqueous electrolyte secondary batteries typified by lithium-ion secondary batteries have been developed. Further, lithium-ion capacitors are known as power storage devices corresponding to applications that require high energy density characteristics and high output characteristics. Furthermore, sodium-ion type batteries and capacitors using sodium, which is lower in cost and more abundant in resources than lithium, are also known.

[0004] In such batteries and capacitors, for various purposes, a process of pre-doping an alkali metal into an electrode (generally called pre-doping) is adopted. As a method of pre-doping an alkali metal into an electrode, for example, there is a continuous method. In the continuous method, pre-doping is performed while transporting a strip-shaped electrode in a doping solution. In the doping solution, the electrode faces an alkali metal electrode. The continuous method is disclosed in Patent Documents 1 to 4.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] When pre-doping is carried out for a long time using a doping solution with a conventional composition, by-products such as diethyl carbonate are likely to be generated in the doping solution. When by-products are generated, the resistance value of the doping solution increases. Also, when by-products are generated, it becomes difficult to achieve uniform pre-doping.

[0007] In one aspect of the present disclosure, it is preferable to provide a method for manufacturing a doped electrode capable of suppressing the generation of by-products in a doping solution when performing pre-doping.

Means for Solving the Problems

[0008] One aspect of the present disclosure is a method for manufacturing a doped electrode including an active material layer doped with an alkali metal. In the method for manufacturing a doped electrode, a strip-shaped electrode including an active material layer is conveyed along a path passing through a doping tank containing a doping solution including alkali metal ions and an aprotic organic solvent and a counter electrode unit, and in the doping tank, the counter electrode unit and the strip-shaped electrode including the active material layer are electrically connected via the doping solution. The content ratio of dimethyl carbonate in the aprotic organic solvent is 40 vol% or more and 95 vol% or less.

[0009] According to the method for manufacturing a doped electrode which is one aspect of the present disclosure, it is possible to suppress the generation of by-products in the doping solution when performing pre-doping.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0011] Exemplary embodiments of the present disclosure will be described with reference to the drawings. <First Embodiment> 1. Configuration of Electrode 1 Based on FIGS. 1 and 2, the configuration of electrode 1 will be described. Electrode 1 has a strip shape. Electrode 1 includes a current collector 3 and an active material layer 5. The current collector 3 has a strip shape. The active material layer 5 is formed on both surfaces of the current collector 3, respectively.

[0012] On the surface of electrode 1, there are an active material layer formation part 6 and an active material layer non-formation part 7. The active material layer formation part 6 is the part where the active material layer 5 is formed. The active material layer non-formation part 7 is the part where the active material layer 5 is not formed. In the active material layer non-formation part 7, the current collector 3 is exposed.

[0013] The active material layer non-formation part 7 has a strip shape extending in the longitudinal direction L of electrode 1. The active material layer non-formation part 7 is located at the end of electrode 1 in the width direction W of electrode 1.

[0014] As the current collector 3, for example, a metal foil such as copper, nickel, or stainless steel is preferable. Also, the current collector 3 may be one on which a conductive layer mainly composed of a carbon material is formed on the metal foil. The thickness of the current collector 3 is, for example, 5 to 50 μm.

[0015] The active material layer 5 can be produced, for example, by applying a slurry containing an active material and a binder onto the current collector 3 and drying it.

[0016] Examples of the binder include rubber-based binders such as styrene-butadiene rubber (SBR) and NBR; fluorine-based resins such as polytetrafluoroethylene and polyvinylidene fluoride; polypropylene, polyethylene, and fluorine-modified (meth)acrylic binders as disclosed in JP-A-2009-246137, etc.

[0017] In addition to the active material and the binder, the slurry may contain other components. 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, metal powder, etc. Examples of the thickener include carboxymethyl cellulose, its Na salt or ammonium salt, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein, etc.

[0018] 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 a capacitor that utilizes insertion and desorption of alkali metal ions. The active material may be a negative electrode active material or a positive electrode active material.

[0019] 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, graphitizable carbon, non-graphitizable carbon, and composite carbon materials in which graphite particles are coated with carbonized pitch or resin. Specific examples of the carbon material include the carbon materials described in JP-A-2013-258392. Specific examples of the materials containing metals or semimetals that can be alloyed with lithium or oxides thereof include the materials described in JP-A-2005-123175 and JP-A-2006-107795.

[0020] Examples of the positive electrode active material include transition metal oxides, sulfur-based active materials, etc. Examples of the transition metal oxides include cobalt oxide, nickel oxide, manganese oxide, vanadium oxide, etc. Examples of the sulfur-based active materials include elemental sulfur, metal sulfides, etc. Either the positive electrode active material or the negative electrode active material may be composed of a single substance or may be composed of a mixture of two or more substances.

[0021] The active material contained in the active material layer 5 is pre-doped with an alkali metal using the electrode manufacturing system 11 described later. As the alkali metal to be pre-doped into the active material, lithium or sodium is preferable, and lithium is particularly preferable. When the electrode 1 is used for manufacturing an electrode of 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.

[0022] 2. Configuration of Electrode Manufacturing System 11 The configuration of the electrode manufacturing system 11 will be described with reference to FIGS. 3 to 5. As shown in FIG. 3, the electrode manufacturing system 11 includes an electrolytic solution treatment tank 15, doping tanks 17, 19, 21, washing tanks 23A, 23B, 23C, 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, 79, 81, 83, 85, 87, 89, 91, 93, 201, 203, 205, 207, 209, 211 (hereinafter, these may be collectively referred to as a conveying roller group), a supply roll 101, a take-up roll 103, a support base 105, a circulation filtration unit 107, six power supplies 109, 110, 111, 112, 113, 114, a tab cleaner 117, a recovery unit 119, an end sensor 121, and a blower 213.

[0023] The electrolytic solution treatment tank 15 is a rectangular tank with an open top. The bottom surface of the electrolytic solution treatment tank 15 has a substantially U-shaped cross-sectional shape. The electrolytic solution treatment tank 15 is provided with a partition plate 123. The partition plate 123 is supported by a support rod 125 passing through 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 electrolytic solution treatment tank 15 into two spaces.

[0024] A conveying roller 33 is attached to the lower end of the partition plate 123. The partition plate 123 and the conveying roller 33 are supported by a support rod 127 passing through them. Note that the vicinity of the lower end of the partition plate 123 is notched so as not to contact the conveying roller 33. There is a space between the conveying roller 33 and the bottom surface of the electrolytic solution treatment tank 15.

[0025] 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 arranged on the side of the supply roll 101 (hereinafter referred to as the upstream side), and the downstream tank 133 is arranged on the side of the take-up roll 103 (hereinafter referred to as the downstream side).

[0026] First, the configuration of the upstream tank 131 will be described. The upstream tank 131 is a rectangular tank with an open top. The bottom surface of the upstream tank 131 has a substantially U-shaped cross-sectional shape. The upstream tank 131 is provided with a partition plate 135 and four counter electrode units 137, 139, 141, and 143.

[0027] The partition plate 135 is supported by a support rod 145 passing 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 inside of the upstream tank 131 into two spaces. A conveying roller 40 is attached to the lower end of the partition plate 135. The partition plate 135 and the conveying roller 40 are supported by a support rod 147 passing through them. Note that the vicinity of the lower end of the partition plate 135 is notched so as not to contact the conveying roller 40. There is a space between the conveying roller 40 and the bottom surface of the upstream tank 131.

[0028] 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 so as 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.

[0029] 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.

[0030] Note that the counter electrode units 137, 139, 141, and 143 may be connected to different power sources respectively. In this case, the counter electrode units 137, 139, 141, and 143 can be controlled respectively. Also, according to the doping condition of the electrode 1 in the doping process, it becomes easier to perform electrical adjustment of the counter electrode units 137, 139, 141, and 143. As a result, it becomes easier to manufacture the desired doped electrode 1A. The doped electrode 1A is an electrode 1 including an active material layer 5 doped with an alkali metal.

[0031] The counter electrode units 137, 139, 141, and 143 have the same configuration. Here, based on FIG. 5, the configuration of the counter electrode unit 137 will be described.

[0032] The counter electrode unit 137 includes a frame body 401, a bus bar 403, a copper plate 407, a lithium plate 409, and a mask 411. The frame body 401 is a box-shaped member with an opening on the side of the electrode 1. The frame body 401 is made of polypropylene. The bus bar 403 is a conductive member. The material of the bus bar 403 is, for example, copper, nickel, titanium, etc. Most of the bus bar 403 is accommodated in the frame body 401. One end of the bus bar 403 protrudes outside the frame body 401. The bus bar 403 is electrically connected to the power source.

[0033] The copper plate 407 and the lithium plate 409 are housed in the frame 401. The lithium plate 409 is electrically connected to the power source via the copper plate 407 and the bus bar 403. As shown in the plan view of FIG. 5, the mask 411 exposes the portion of the lithium plate 409 that faces the active material layer forming portion 6 of the electrode 1 and covers the portion that faces the non-active material layer forming portion 7. The mask 411 suppresses the precipitation of lithium on the non-active material layer forming portion 7 during pre-doping. Therefore, it becomes easy to manufacture the power storage device using the doped electrode 1A.

[0034] The downstream tank 133 basically has the same configuration as the upstream tank 131. However, inside the downstream tank 133, there is a conveying roller 46 instead of the conveying roller 40. Also, the counter electrode units 137, 139, 141, 143 provided in the downstream tank 133 are connected to one pole of the power source 110.

[0035] The doping tank 19 basically has the same configuration as the doping tank 17. However, inside the doping tank 19, there are conveying rollers 52 and 58 instead of the conveying rollers 40 and 46. Also, the counter electrode units 137, 139, 141, 143 provided in the upstream tank 131 of the doping tank 19 are connected to one pole of the power source 111. Further, the counter electrode units 137, 139, 141, 143 provided in the downstream tank 133 of the doping tank 19 are connected to one pole of the power source 112.

[0036] The doping tank 21 basically has the same configuration as the doping tank 17. However, inside the doping tank 21, there are conveying rollers 64 and 70 instead of the conveying rollers 40 and 46. Also, the counter electrode units 137, 139, 141, 143 provided in the upstream tank 131 of the doping tank 21 are connected to one pole of the power source 113. Further, the counter electrode units 137, 139, 141, 143 provided in the downstream tank 133 of the doping tank 21 are connected to one pole of the power source 114.

[0037] The cleaning tanks 23A, 23B, and 23C each basically have the same configuration as the electrolytic solution treatment tank 15. However, inside the cleaning tanks 23A, 23B, and 23C, there is a conveying roller 75 instead of the conveying roller 33.

[0038] On the electrode 1 that has passed through the doping bath 21, the doping solution taken out from the doping bath 21 adheres. In the cleaning baths 23A, 23B, and 23C, the doping solution adhering to the electrode 1 is efficiently removed. Therefore, the handling of the electrode 1 in the next process becomes easy.

[0039] The cleaning baths 23A, 23B, and 23C contain, for example, the following cleaning liquids. The cleaning liquid is preferably an organic solvent and preferably contains an aprotic solvent having a boiling point of 150°C or lower at 1 atm. Examples of the aprotic solvent having a boiling point of 150°C or lower at 1 atm include at least one selected from carbonate solvents, ester solvents, ether solvents, hydrocarbon solvents, ketone solvents, and nitrile solvents. Among these, carbonate solvents are preferred. As the carbonate solvent, at least one selected from dimethyl carbonate, diethyl carbonate, methylpropyl carbonate, and ethylmethyl carbonate is particularly preferred. By using such a cleaning liquid, it becomes easy to remove the cleaning liquid from the electrode 1 after cleaning.

[0040] Note that in the cleaning baths 23A, 23B, and 23C, since the doping solution taken out from the doping bath 21 accumulates, it is preferable to maintain the cleaning liquid at a certain quality by adding or replacing the cleaning liquid. As a method for grasping the quality of the cleaning liquid, a method of installing sensors such as an insulation resistance meter and a conductivity meter in the cleaning baths 23A, 23B, and 23C and periodically checking the values measured by these sensors can be mentioned.

[0041] Among the conveying roller group, the conveying rollers 37, 39, 43, 45, 49, 51, 55, 57, 61, 63, 67, and 69 are made of conductive materials. The conveying rollers 37, 39, 43, 45, 49, 51, 55, 57, 61, 63, 67, and 69 correspond to the conductive power supply rollers. Examples of the conductive material include stainless steel, gold, copper, rhodium, etc. Particularly, copper is preferable as the conductive material. The conductive material may be composed of 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, high-quality doped electrodes 1A can be mass-produced.

[0042] Among the conveying roller group, the conveying rollers other than the conductive power supply rollers are made of elastomer except for the bearing parts. The conveying roller group conveys the electrode 1 along a certain path. As the path for the conveying roller group to convey the electrode 1, there are a cleaning execution path and a cleaning omission path. The cleaning execution path is a path that sequentially passes from the supply roll 101, into the electrolytic solution treatment tank 15, into the doping tank 17, into the doping tank 19, into the doping tank 21, into at least one of the cleaning tanks 23A, 23B, and 23C, and into the tab cleaner 117, and reaches the take-up roll 103. In the cleaning execution path, the number of cleaning tanks through which the doped electrode 1A passes can be arbitrarily selected from 1 to 3.

[0043] The cleaning omission path is basically the same as the cleaning execution path, but after passing through the doping tank 21, it does not pass through the cleaning tanks 23A, 23B, and 23C and proceeds to the tab cleaner 117.

[0044] Also, in both the cleaning execution path and the cleaning omission path, there are two types of paths after passing through the tab cleaner 117. One path is the path that is conveyed by the conveying rollers 201, 203, 205, 207, 209, and 211 after passing through the tab cleaner 117, and then is conveyed by the conveying rollers 85, 87, 89, 91, and 93 (hereinafter referred to as the long drying path KL).

[0045] Another path is the path that, after passing through the tab cleaner 117, is conveyed by the conveying rollers 85, 87, 89, 91, 93 via the conveying rollers 201, 203 (hereinafter referred to as the short drying path KS).

[0046] Among the paths through which the conveying roller group conveys the electrode 1, the part passing through the electrolytic solution treatment tank 15 first moves downward via the conveying rollers 29, 31, and then the moving direction is changed upward by the conveying roller 33.

[0047] Also, the part of the path through which the conveying roller group conveys the electrode 1 and passes through the dope tank 17 is as follows. First, the moving direction is changed downward by the conveying roller 37, and it moves downward through the space 149 of the upstream tank 131. Next, the moving direction is changed upward by the conveying roller 40, and it moves upward through the space 151 of the upstream tank 131. Next, the moving direction is changed downward by the conveying rollers 41, 43, and it moves downward through the space 149 of the downstream tank 133. Next, the moving direction is changed upward by the conveying roller 46, and it moves upward through the space 151 of the downstream tank 133. Finally, the moving direction is changed horizontally by the conveying roller 47, and it heads towards the dope tank 19.

[0048] Also, the part of the path through which the conveying roller group conveys the electrode 1 and passes through the dope tank 19 is as follows. First, the moving direction is changed downward by the conveying roller 49, and it moves downward through the space 149 of the upstream tank 131. Next, the moving direction is changed upward by the conveying roller 52, and it moves upward through the space 151 of the upstream tank 131. Next, the moving direction is changed downward by the conveying rollers 53, 55, and it moves downward through the space 149 of the downstream tank 133. Next, the moving direction is changed upward by the conveying roller 58, and it moves upward through the space 151 of the downstream tank 133. Finally, the moving direction is changed horizontally by the conveying roller 59, and it heads towards the dope tank 21.

[0049] Also, among the paths through which the transport roller group transports the electrode 1, the portion passing through the doping tanks 21 is as follows. First, the moving direction is changed downward by the transport roller 61, and it moves downward in the space 149 of the upstream tank 131. Next, the moving direction is changed upward by the transport roller 64, and it moves upward in the space 151 of the upstream tank 131. Next, the moving direction is changed downward by the transport rollers 65 and 67, and it moves downward in the space 149 of the downstream tank 133. Next, the moving direction is changed upward by the transport roller 70, and it moves upward in the space 151 of the downstream tank 133. Finally, the moving direction is changed to the horizontal direction by the transport roller 71, and it heads toward the cleaning tank 23.

[0050] Also, among the cleaning execution paths, the portion passing through the cleaning tanks 23A, 23B, and 23C is first a path in which the moving direction is changed downward by the transport roller 73 and it moves downward, and then the moving direction is changed upward by the transport roller 75.

[0051] The supply roll 101 is winding the electrode 1. 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.

[0052] The transport roller group pulls out and transports the electrode 1 held by the supply roll 101. The take-up roll 103 winds up and stores the electrode 1 transported by the transport roller group. When the electrode 1 is transported along the 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 with an alkali metal is a method of electrically doping the alkali metal into the active material using the counter electrode units 137, 139, 141, and 143 provided opposite to the electrode 1 in the doping tanks 17, 19, and 21. By doping the active material layer 5 with an alkali metal, the electrode 1 becomes a doped electrode 1A including the active material layer 5 doped with an alkali metal. The electrode 1 stored in the take-up roll 103 is the doped electrode 1A.

[0053] The support base 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 base 105 can be changed. The circulation filtration units 107 are respectively provided in the dope tanks 17, 19, 21. The circulation filtration unit 107 includes a filter 161, a pump 163, and a pipe 165.

[0054] In the circulation filtration unit 107 provided in the dope tank 17, the pipe 165 is a circulation pipe that exits the dope tank 17, sequentially passes through the pump 163 and the filter 161, 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 matters in the dope solution are filtered by the filter 161. Examples of the foreign matters include foreign matters precipitated from the dope solution and foreign matters generated from the electrode 1. The material of the filter 161 is, for example, a resin such as polypropylene or polytetrafluoroethylene. The pore diameter of the filter 161 can be set as appropriate. The pore diameter of the filter 161 is, for example, 0.2 μm or more and 50 μm or less.

[0055] The circulation filtration units 107 provided in the dope tanks 19 and 21 also have the same configuration and exhibit the same operational effects. In FIGS. 3 and 4, the description of the dope solution is omitted for convenience.

[0056] One terminal of the power source 109 is connected to the conveying rollers 37, 39. The other terminal of the power source 109 is connected to the counter electrode units 137, 139, 141, 143 provided in the upstream tank 131 of the dope tank 17. The electrode 1 contacts the conveying rollers 37, 39. The electrode 1 and the counter electrode units 137, 139, 141, 143 are in the dope solution which is the electrolyte. Therefore, in the upstream tank 131 of the dope tank 17, the electrode 1 and the counter electrode units 137, 139, 141, 143 are electrically connected via the electrolyte.

[0057] One terminal of the power supply 110 is connected to the conveying rollers 43 and 45. Also, the other terminal of the power supply 110 is connected to the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 of the doping tank 17. The electrode 1 contacts the conveying rollers 43 and 45. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the doping solution which is the electrolytic solution. Therefore, in the downstream tank 133 of the doping tank 17, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolytic solution.

[0058] One terminal of the power supply 111 is connected to the conveying rollers 49 and 51. Also, the other terminal of the power supply 111 is connected to the counter electrode units 137, 139, 141, and 143 provided in the upstream tank 131 of the doping tank 19. The electrode 1 contacts the conveying rollers 49 and 51. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the doping solution which is the electrolytic solution. Therefore, in the upstream tank 131 of the doping tank 19, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolytic solution.

[0059] One terminal of the power supply 112 is connected to the conveying rollers 55 and 57. Also, the other terminal of the power supply 112 is connected to the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 of the doping tank 19. The electrode 1 contacts the conveying rollers 55 and 57. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the doping solution which is the electrolytic solution. Therefore, in the downstream tank 133 of the doping tank 19, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolytic solution.

[0060] One terminal of the power supply 113 is connected to the conveying rollers 61 and 63. Also, the other terminal of the power supply 113 is connected to the counter electrode units 137, 139, 141, and 143 provided in the upstream tank 131 of the doping tank 21. The electrode 1 contacts the conveying rollers 61 and 63. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the doping solution which is the electrolytic solution. Therefore, in the upstream tank 131 of the doping tank 21, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolytic solution.

[0061] One terminal of the power supply 114 is connected to the conveying rollers 67 and 69. The other terminal of the power supply 114 is connected to the counter electrode units 137, 139, 141, and 143 provided in the downstream tank 133 of the doping tank 21. The electrode 1 contacts the conveying rollers 67 and 69. The electrode 1 and the counter electrode units 137, 139, 141, and 143 are in the doping solution which is the electrolytic solution. Therefore, in the downstream tank 133 of the doping tank 21, the electrode 1 and the counter electrode units 137, 139, 141, and 143 are electrically connected via the electrolytic solution.

[0062] The tab cleaner 117 cleans the non-active material layer formed portion 7 of the doped electrode 1A. If residual organic components derived from the doping solution or the like remain in the non-active material layer formed portion 7 of the doped electrode 1A, welding defects are likely to occur when welding the non-active material layer formed portion 7.

[0063] After cleaning by the tab cleaner 117, the amount of residual organic components on the non-active material layer formed portion 7 can be measured. As a measurement method, for example, the total reflection measurement method of a Fourier transform infrared spectrophotometer can be mentioned. The characteristic peak of the residual organic component is in the range of wave number 1180 cm -1 ~1250 cm -1 . Therefore, based on the absorbance peak area value in this range, the amount of residual organic components can be measured.

[0064] After cleaning by the tab cleaner 117, the quality of the doped electrode 1A can be evaluated based on the amount of residual organic components on the non-active material layer formed portion 7. For example, whether the absorbance peak area value in the range of wave number 1180 cm -1 ~1250 cm -1 is 0.1 or less can be used to evaluate the quality of the doped electrode 1A. If the absorbance peak area value is 0.1 or less, it can be determined that the non-active material layer formed portion 7 is sufficiently cleaned.

[0065] The recovery unit 119 is disposed in each of the electrolytic solution treatment tank 15, the dope tanks 17, 19, 21, and the cleaning tanks 23A, 23B, 23C. The recovery unit 119 recovers the liquid taken out of the tank by the electrode 1 and returns it to the tank.

[0066] The end sensor 121 detects the position of the end in the width direction W of the electrode 1. An end position adjustment unit (not shown) adjusts the positions in the width direction W of the supply roll 101 and the take-up roll 103 based on the detection result of the end sensor 121.

[0067] There are a plurality of blowers 213. The plurality of blowers 213 are arranged along the path through which the dope electrode 1A is conveyed. Some of the blowers 213 blow gas onto the conveyed dope electrode 1A regardless of whether the path of the dope electrode 1A is the long drying path KL or the short drying path KS. Other blowers 213 blow gas onto the dope electrode 1A being conveyed along the long drying path KL. Therefore, when the path of the dope electrode 1A is the long drying path KL, the dope electrode 1A is blown with gas for a longer time than when it is the short drying path KS.

[0068] The gas blown by the blower 213 is preferably a gas inert to the active material doped with an alkali metal. Examples of such a gas include helium gas, neon gas, argon gas, nitrogen gas, dehumidified air from which moisture has been removed, and the like. The gas may be a gas composed of a single component or a mixed gas composed of two or more components.

[0069] When the cleaning bypass route is selected and the doped electrode 1A passes through the tab cleaner 117, a doping solution adheres to the surface of the doped electrode 1A. By blowing gas onto the doped electrode 1A with the blower 213, the solvent of the doping solution evaporates. Components of the doping solution (hereinafter referred to as residual components) remain on the surface of the doped electrode 1A. The residual components are those in which one or more of the components contained in the doping solution adhering to the doped electrode 1A remain. 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 coating amount a described later.

[0070] 3. Composition of the doping solution When using the electrode manufacturing system 11, the electrolyte treatment tank 15 and the doping tanks 17, 19, 21 are filled with a doping solution. The doping solution contains alkali metal ions and a solvent. The doping solution is an electrolyte.

[0071] Examples of the solvent include organic solvents. As the organic solvent, an aprotic organic solvent is preferred. The solvent consists of, for example, only aprotic organic solvents. Examples of the aprotic organic solvent include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, fluoroethylene 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).

[0072] When the solvent is the above-mentioned aprotic organic solvent, it becomes possible to efficiently dope the electrode 1. Further, by using the doped electrode 1A doped with the above-mentioned aprotic organic solvent, a secondary battery with high battery stability can be obtained.

[0073] As the aprotic organic solvent, an organic solvent belonging to a specific group is preferable. Examples of the organic solvent belonging to the specific group include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinylene carbonate, vinyl ethylene carbonate, ethylene carbonate, fluoroethylene carbonate, and propylene carbonate.

[0074] When the solvent is an organic solvent belonging to a specific group, it becomes possible to dope electrode 1 particularly efficiently. Further, by using the doped electrode 1A doped with an organic solvent belonging to a specific group, a secondary battery with particularly high battery stability can be obtained.

[0075] Also, as the organic solvent, for example, ionic liquids such as quaternary imidazolium salts, quaternary pyridinium salts, quaternary pyrrolidinium salts, and quaternary piperidinium salts can be used. The organic solvent may consist of a single component or may be a mixed solvent of two or more components.

[0076] The content ratio of dimethyl carbonate in the aprotic organic solvent is preferably 40 vol% or more and 95 vol% or less. When the content ratio of dimethyl carbonate in the aprotic organic solvent is 40 vol% or more and 95 vol% or less, even when pre-doping is carried out for a long time, diethyl carbonate is less likely to be generated in the doping solution. In particular, even when pre-doping is continuously carried out in a situation where the potential of electrode 1 (hereinafter referred to as the potential of electrode 1) with reference to the lithium metal electrode 505 for reference described later is 0 V or less, diethyl carbonate is less likely to be generated in the doping solution.

[0077] Note that the situation where the potential of electrode 1 continuously becomes 0 V or less for a long time is a situation of a strong reducing atmosphere. A situation of a strong reducing atmosphere does not occur in a general power storage device. If a situation of a strong reducing atmosphere occurs in a general power storage device, it is presumed that by-products such as diethyl carbonate are likely to be generated.

[0078] In addition, dimethyl carbonate is an organic solvent with a relatively low boiling point among the organic solvents belonging to the above specific group. Therefore, when the content ratio of dimethyl carbonate in the aprotic organic solvent is 40 vol% or more and 95 vol% or less, it is easy to adjust the mass of the dope solution remaining on the doped electrode 1A.

[0079] More preferably, the content ratio of dimethyl carbonate in the aprotic organic solvent is 60 vol% or more and 85 vol% or less. When the content ratio of dimethyl carbonate in the aprotic organic solvent is 60 vol% or more and 85 vol% or less, even when pre-doping is carried out for a long time, diethyl carbonate is less likely to be generated in the dope solution, and it is easy to adjust the mass of the dope solution remaining on the doped electrode 1A.

[0080] Preferably, the content ratio of ethyl methyl carbonate in the aprotic organic solvent is 0 vol% or more and 30 vol% or less. When the content ratio of ethyl methyl carbonate in the aprotic organic solvent is 0 vol% or more and 30 vol% or less, even when pre-doping is carried out for a long time in a situation where the potential of the electrode 1 becomes 0 V or less, the efficiency of pre-doping can be increased, and diethyl carbonate is less likely to be generated in the dope solution.

[0081] The reason is presumably that by setting the content ratio of dimethyl carbonate in the aprotic organic solvent within the above range and setting the content ratio of ethyl methyl carbonate to 0 vol% or more and 30 vol% or less, the reaction between the components of the solvent is suppressed even in a situation where the potential of the electrode 1 becomes 0 V or less. Examples of the reaction between the components of the solvent include transesterification reactions.

[0082] The content ratio of ethyl methyl carbonate in the aprotic organic solvent is more preferably 0 vol% or more and 20 vol% or less, and particularly preferably 0 vol% or more and 8 vol% or less. When the content ratio of dimethyl carbonate in the aprotic organic solvent is within the above range, even when pre-doping is carried out for a long time, the efficiency of pre-doping becomes higher, and diethyl carbonate is less likely to be generated in the doping solution.

[0083] The content ratio of cyclic carbonate in the aprotic organic solvent is preferably 5 vol% or more and 40 vol% or less. When the content ratio of cyclic carbonate in the aprotic organic solvent is 5 vol% or more and 40 vol% or less, the resistance of the doping solution decreases, and even when pre-doping is carried out for a long time, by-products such as diethyl carbonate and carbonate-based oligomers are less likely to be generated in the doping solution.

[0084] The alkali metal ions contained in the doping solution are the ions constituting the alkali metal salt. The alkali metal salt is preferably a lithium salt or a sodium salt. As the anion part constituting the alkali metal salt, for example, PF6 - , PF3(C2F5)3 - , PF3(CF3)3 - and other phosphorus anions having fluorine groups; BF4 - , BF2(CF)2 - , BF3(CF3) - , B(CN)4 - and other boron anions having fluorine groups or cyano groups; N(FSO2)2 - , N(CF3SO2)2 - , N(C2F5SO2)2 - and other sulfonylimide anions having fluorine groups; CF3SO3 - and other organic sulfonic acid anions having fluorine groups can be mentioned.

[0085] The concentration of the alkali metal salt in the doping solution is preferably 0.1 mol / L or more, 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, the pre-doping of the alkali metal proceeds efficiently.

[0086] The doping solution can further contain additives such as vinylene carbonate, vinyl ethylene carbonate, 1-fluoroethylene carbonate, 1-(trifluoromethyl)ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, and diethyl sulfone.

[0087] The doping solution can further contain a flame retardant such as a phosphazene compound. From the viewpoint of effectively controlling the thermal runaway reaction during alkali metal doping, the addition amount of the flame retardant 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 with respect to 100 parts by mass of the doping solution. Also, from the viewpoint of obtaining a high-quality doped electrode 1A, the addition amount of the flame retardant 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 with respect to 100 parts by mass of the doping solution.

[0088] 4. Manufacturing method of the doped electrode 1A using the 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-described path. Next, the electrolytic solution treatment tank 15, the doping tanks 17, 19, 21, and the washing tanks 23A, 23B, 23C are raised and set at the fixed positions shown in Figure 3.

[0089] Next, the doping solution is stored in the electrolytic solution treatment tank 15 and the doping tanks 17, 19, 21. The doping solution is the one described in the above "3. Composition of the doping solution". When the washing execution path is selected as the conveyance path, the cleaning liquid is stored in the washing tanks 23A, 23B, 23C.

[0090] Next, the transport roller group transports the electrode 1 along the above-described path from the supply roll 101 to the take-up roll 103. The path for transporting the electrode 1 is a path that passes through the dope tanks 17, 19, and 21. When the electrode 1 passes through the dope tanks 17, 19, and 21, the active material contained in the active material layer 5 is pre-doped with an alkali metal.

[0091] Furthermore, when selecting a cleaning execution path 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.

[0092] Furthermore, the transport roller group continuously transports the electrode 1 to the tab cleaner 117. Among the electrode 1, the portion transported to the tab cleaner 117 is the portion where the pre-doping process has already been performed and has become the doped electrode 1A. The tab cleaner 117 cleans the non-active material layer forming portion 7 among the doped electrodes 1A.

[0093] The doped electrode 1A may be a positive electrode or a negative electrode. When manufacturing a positive electrode, the electrode manufacturing system 11 dopes the positive electrode active material with an alkali metal. When manufacturing a negative electrode, the electrode manufacturing system 11 dopes the negative electrode active material with an alkali metal.

[0094] When lithium is occluded in the negative electrode active material of a lithium-ion capacitor, the doping amount of the alkali metal is preferably 70 to 95% with respect to the theoretical capacity of the negative electrode active material. When lithium is occluded in the negative electrode active material of a lithium-ion secondary battery, the doping amount of the alkali metal is preferably 10 to 30% with respect to the theoretical capacity of the negative electrode active material.

[0095] 5. Method for manufacturing a secondary battery Examples of the secondary battery include a lithium ion secondary battery and the like. The secondary battery includes an electrode cell. The electrode cell has a configuration in which a negative electrode and a positive electrode are laminated. In the secondary battery, for example, the negative electrode is manufactured by the above-mentioned "4. Method for manufacturing the doped electrode 1A using the electrode manufacturing system 11". Next, the negative electrode and the positive electrode are laminated to form an electrode cell.

[0096] 6. Effects of the method for manufacturing the doped electrode (6-1) In the method for manufacturing the doped electrode of the present disclosure, the content ratio of dimethyl carbonate in the aprotic organic solvent contained in the doping solution can be 40 vol% or more and 95 vol% or less. In that case, it is possible to suppress the generation of by-products in the doping solution when performing pre-doping. In addition, it is easy to adjust the mass of the doping solution remaining in the doped electrode 1A.

[0097] In the method for manufacturing the doped electrode of the present disclosure, the content ratio of dimethyl carbonate in the aprotic organic solvent contained in the doping solution can be 60 vol% or more and 85 vol% or less. In that case, it is possible to further suppress the generation of by-products in the doping solution when performing pre-doping. In addition, it is easier to adjust the mass of the doping solution remaining in the doped electrode 1A.

[0098] (6-2) In the method for manufacturing the doped electrode of the present disclosure, the content ratio of cyclic carbonate in the aprotic organic solvent contained in the doping solution can be 5 vol% or more and 40 vol% or less. In that case, since the resistance of the doping solution decreases, it is possible to suppress the generation of by-products in the doping solution when performing pre-doping.

[0099] (6-3) In the method for manufacturing the doped electrode of the present disclosure, the electrode 1 is pulled out from the supply roll 101, conveyed along the conveyance path, and wound around the take-up roll 103. Further, in the method for manufacturing the doped electrode of the present disclosure, while continuously conveying the electrode 1, in the doping tanks 17, 19, 21, the counter electrode units 137, 139, 141, 143 and the electrode 1 are electrically connected via the doping solution. Therefore, the method for manufacturing the doped electrode of the present disclosure is excellent in productivity.

[0100] (6-4) In the method for manufacturing the doped electrode of the present disclosure, when the counter electrode units 137, 139, 141, 143 and the electrode 1 are electrically connected through the doping solution in the doping tanks 17, 19, 21, the potential of the electrode 1 can be set to -10 V or more and 0 V or less.

[0101] If the potential of the electrode 1 is within the above range, a high current amount can be applied to the electrode 1, so that the productivity of the doped electrode 1A can be improved.

[0102] In addition, the situation where the potential of the electrode 1 continuously becomes 0 V or less for a long time is a situation of a strong reducing atmosphere. A situation of a strong reducing atmosphere cannot occur in a general power storage device. If a situation of a strong reducing atmosphere occurs in a general power storage device, it is presumed that by-products such as diethyl carbonate are likely to be generated.

[0103] The reference lithium metal electrode 505 is installed at a location other than the space where the counter electrode units 137, 139, 141, 143 and the electrode 1 face each other and within 7 mm from the electrode 1.

[0104] (6-5) When the cleaning-omission path is selected as the conveyance path of the electrode 1, the doped electrode 1A with the doping solution attached can be dried in the long drying path KL or the short drying path KS. Drying means removing the solvent of the doping solution. The dried doped electrode 1A preferably contains 5 to 40 parts by mass of residual components with respect to 100 parts by mass of the active material layer 5. By using the doped electrode 1A containing 5 to 40 parts by mass of residual components with respect to 100 parts by mass of the active material layer 5, a secondary battery with high battery stability can be manufactured.

[0105] The dried doped electrode 1A more preferably contains 10 to 30 parts by mass of residual components with respect to 100 parts by mass of the active material layer 5, and particularly preferably contains 15 to 25 parts by mass of residual components with respect to 100 parts by mass of the active material layer 5.

[0106] When the dried doped electrode 1A contains a residual component of 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the active material layer 5, a secondary battery with higher battery stability can be manufactured. When the dried doped electrode 1A contains a residual component of 15 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the active material layer 5, a secondary battery with particularly high battery stability can be manufactured.

[0107] When the cleaning omission path is selected as the transport path of the electrode 1, the process of cleaning the doped electrode 1A is unnecessary, so the productivity of the doped electrode 1A is high.

[0108] Also, even when the cleaning execution path is selected as the transport path of the electrode 1, if any one 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.

[0109] The doped electrode 1A containing the residual component can be manufactured by an electrode manufacturing system not provided with a cleaning mechanism such as the cleaning tanks 23A, 23B, 23C, etc. Therefore, the electrode manufacturing system can be miniaturized.

[0110] 7. Examples (Example 1) (i) Manufacture 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 in width, 500 m in length, and 8 μm in thickness. The surface roughness Ra of the current collector 3 was 0.1 μm. The current collector 3 was made of copper foil. The active material layer 5 was formed on both surfaces of the current collector 3 respectively. The active material layer 5 was a negative electrode active material layer.

[0111] The coating amount of the active material layer 5 was 25 g / m per side 2It was as follows. As 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 the end in the width direction W of the current collector 3. The width of the non-active material layer portion 7 at the other end in the width direction W of the current collector 3 was 10 mm. The non-active material layer portion 7 is a portion where the active material layer 5 is not formed. Thereafter, by performing drying, the electrode 1 was obtained.

[0112] 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 graphite-based active material. The acetylene black corresponded to a conductive agent.

[0113] (ii) Manufacture of counter electrode units 137, 139, 141, 143 The counter electrode unit 137 shown in FIG. 5 was manufactured. The size of the copper plate 407 was 100 mm in length, 220 mm in width, and 3 mm in thickness. A lithium plate 409 was attached onto the copper plate 407. The size of the lithium plate 409 was 810 mm in length, 120 mm in width, and 2 mm in thickness. The lithium plate 409 was pressure-bonded to the copper plate 407 using a roll press device to obtain the counter electrode unit 137. The linear pressure in the pressure bonding was 5 kgf / cm. The counter electrode units 139, 141, and 143 were obtained in the same manner.

[0114] (iii) Manufacture of doped electrode 1A The electrode manufacturing system 11 shown in FIG. 3 was prepared and the electrode 1 was passed through the paper. Further, the counter electrode units 137, 139, 141, and 143 were installed in the doping tanks 17, 19, and 21, respectively. Next, a doping solution was supplied into the doping tanks 17, 19, and 21. The doping solution was a solution containing 1.4 M of LiPF6. The solvent of the doping solution was an aprotic organic solvent. The doping solution did not contain a solvent other than the aprotic organic solvent.

[0115] The aprotic organic solvent was a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 30:5:65. That is, when the total volume of the solvent contained in the dope solution was set to 100, the volume ratio of EC was 30, the volume ratio of EMC was 5, and the volume ratio of DMC was 65.

[0116] The dope tanks 17, 19, and 21 were in a state of accommodating the dope solution and the counter electrode units 137, 139, 141, and 143. The conveyance path of the electrode 1 was set as the cleaning execution path.

[0117] Next, the electrode 1 and the counter electrode units 137, 139, 141, and 143 passed through the paper in the electrode manufacturing system 11 were connected to a DC power supply with a current-voltage monitor. While continuously conveying the electrode 1 at a speed of 1.7 m / min, a current of 46.7 A was passed through the entire electrode manufacturing system 11. At this time, the pre-doping current density per unit area of the electrode 1 was 12.2 mA / cm 2 It was. Also, at this time, the center in the width direction W of the active material layer 5 provided in the electrode 1 and the center in the width direction W of the lithium plate 409 provided in the counter electrode units 137, 139, 141, and 143 were coincident.

[0118] After passing through the dope tank 21, the doped electrode 1A was washed in the washing tanks 23A, 23B, and 23C and then advanced to the tab cleaner 117. After passing through the tab cleaner 117, the doped electrode 1A advanced to the drying path. In the drying path, the doped electrode 1A was blown with gas from the blower 213 and dried. The gas blown by the blower 213 was nitrogen. The flow rate of the blower 213 was 5 L / min per unit. The number of blowers 213 that blew gas onto the doped electrode 1A was 6. Predoping was continuously performed for 20 hours under these conditions.

[0119] Table 1 shows the manufacturing conditions of the doped electrode 1A in Example 1, as well as Examples 2 to 8 and Comparative Examples 1 to 3 described below. Table 1 also shows the evaluation results of each example and each comparative example. In Table 1, "having" in the "washing process" means that the path for transporting the electrode 1 is the washing execution path. "Not having" in the "washing process" means that the path for transporting the electrode 1 is the washing omission path.

[0120]

Table 1

[0121] (iv) Measurement of the voltage after pre-doping and confirmation of the presence or absence of Li deposition At the end of pre-doping, the voltage indicated by the DC power supply with a current / voltage monitor connected to the counter electrode units 137, 139, 141, 143 (hereinafter referred to as the voltage after pre-doping) was 4.5V. Also, at the end of pre-doping, no Li deposition was observed on the doped electrode 1A.

[0122] Note that a high voltage after pre-doping causes electrolysis of the doping solution. Therefore, in order to suppress the electrolysis of the doping solution and produce a high-quality doped electrode 1A, it is desirable that the voltage after pre-doping be low.

[0123] (v) Measurement of the negative electrode potential based on the reference lithium metal electrode Before starting pre-doping, as shown in FIG. 6, the reference electrode unit 501 was installed in the doping bath 17. The reference electrode unit 501 included a nickel tab lead 503 and a reference lithium metal electrode 505. The reference lithium metal electrode 505 was attached to the end of the tab lead 503. The shape of the reference lithium metal electrode 505 was a plate shape with a length of 4 mm, a width of 4 mm, and a thickness of 150 μm.

[0124] The position of the reference lithium metal electrode 505 was a position outside the space 507 where the counter electrode unit 137 and the electrode 1 faced each other. The space 507 is the space that overlaps with the lithium plate 409 and the electrode 1 in the plan view of FIG. 6 and is between the lithium plate 409 and the electrode 1 in the cross-sectional view of FIG. 6. Also, the position of the reference lithium metal electrode 505 was a position where the distance from the electrode 1 was 5 mm.

[0125] One terminal of the voltmeter 509 was connected to the end of the tab lead 503 on the side opposite to the reference lithium metal electrode 505, and the other terminal of the voltmeter was connected to the transport roller 37. The transport roller 37 is a conductive power supply roller as described above. The potential of the transport roller 37 was measured with reference to the reference lithium metal electrode 505 by the voltmeter. Since the potential of the transport roller 37 is equal to the potential of the electrode 1, the measured potential is the potential of the electrode 1 (hereinafter referred to as the negative electrode potential) with reference to the reference lithium metal electrode 505. The negative electrode potential was -2.2V.

[0126] (Vi) Measurement of DEC volume ratio After 20 hours of pre-doping, the volume ratio of diethyl carbonate in the solvent contained in the doping solution (hereinafter referred to as the DEC volume ratio) was measured. The measurement method was as follows.

[0127] After 20 hours of pre-doping, the doping solution was taken out from the doping tank 17. The doping solution was diluted 100 times with acetone. Next, gas chromatography analysis was performed on the diluted doping solution.

[0128] By performing gas chromatography analysis on a mixed solvent with a known volume ratio of diethyl carbonate, a calibration curve showing the relationship between the results of the gas chromatography analysis and the DEC volume ratio was prepared in advance. The DEC volume ratio was obtained by applying the results of the gas chromatography analysis of the diluted doping solution to the calibration curve. The detailed conditions of the gas chromatography analysis were as follows.

[0129] Apparatus: Agilent 7890B Column: VF-5ms, length 30 m × inner diameter 0.25 mm × film thickness 1 μm Inlet temperature: 250 °C Split ratio: 20:1 Sample injection volume: 1 μL Column temperature: 40 °C for 3 minutes → heating rate 20 °C / min → 280 °C for 1 minute Carrier gas: He Linear velocity: 46 cm / sec The volume ratio of DEC was 0 vol%. When pre-doping was carried out for a long time, by-products may be generated due to the electrolysis of the doping solution. The main by-product is diethyl carbonate. When a large amount of by-products are generated, the electrical resistance of the doping solution increases, which may cause an increase in the voltage after pre-doping.

[0130] (vii) Calculation of mass ratio X In the obtained doped electrode 1A, the mass ratio X was calculated. The mass ratio X (%) is the value calculated by the following formula 1. (Formula 1) X = (a / b) × 100 a is the solvent loading. The unit of the solvent loading a is g / cm 2 It is. b is the active material layer loading. The unit of the active material layer loading b is g / cm 2 It is.

[0131] The solvent loading a was 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 with DMC solvent and dried. The mass wa2 of the dried sample was measured using an electronic balance. The units of wa1 and wa2 are g, respectively. The solvent loading a was calculated by the following formula 2. (Formula 2) a = (wa1 - wa2) / S S is the area of a sample with a diameter of 16 mm. The unit of S is cm 2 It is.

[0132] The active material layer loading b is calculated by the following formula 3. (Formula 3) b = (wa2 - wa3) / S wa3 is the mass of a 16-mm diameter sample punched out from the current collector 3. The unit of wa3 is g.

[0133] The mass ratio X in the doped electrode 1A was 1%. 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 doped solution in the amount of the mass part of the numerical value of the mass ratio X with respect to 100 mass parts of the active material layer 5.

[0134] (viii) Evaluation of battery stability The battery stability of the doped electrode 1A was evaluated by the following method. Using a Thomson blade of Takahashi Seiki Co., Ltd., a part of the doped electrode 1A was punched out. 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 welding part protruding from one side of the rectangle to the outer peripheral side. The negative electrode was exposed to an environment with a dew point of -45°C in a glove box for 5 hours.

[0135] Next, the negative electrode was brought into a dry room with a dew point of -60°C. In the dry room, an evaluation half-cell was created using the negative electrode. The method for creating the evaluation half-cell was as follows.

[0136] A separator, a counter electrode, and a separator were sequentially laminated on one side of the negative electrode. Also, a separator, a counter electrode, and a separator were sequentially laminated on the opposite side of the negative electrode. As a result, a laminate was obtained. The separator was made of a 35-μm thick polyethylene nonwoven fabric. The counter electrode was a copper lath foil with metallic lithium attached thereto. 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 part protruding from one side of the rectangle to the outer peripheral side.

[0137] Next, the four sides of the laminate were fixed with tape. Next, the terminal welding part of the negative electrode and the terminal welding part of the counter electrode were ultrasonically welded to a copper terminal. The size of the terminal was 5 mm in width, 50 mm in length, and 0.2 mm in thickness.

[0138] 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 in length and 8.0 cm in width. Three sides of the four sides of the two laminate films were fused. As a result, the two laminate films became a bag with only one side open. The laminate was accommodated in the bag.

[0139] Next, the laminate in the bag was vacuum impregnated with an electrolyte solution. The electrolyte solution was a solution containing 1.2 M of LiPF6. The solvent contained in the electrolyte solution was a mixed solution containing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7.

[0140] Next, the one side that had not yet been fused among the four sides of the bag was vacuum fused at -80 kPa. The evaluation half-cell was completed through the above steps.

[0141] The evaluation half-cell was introduced into a constant temperature bath at 25°C. Next, the negative electrode doping capacity rate E represented by the following formula (4) was calculated. The unit of the negative electrode doping capacity rate E is %. (Formula 4) E = (C1 / C2) × 100 C1 is the initial discharge capacity. C2 is the second discharge capacity. The units of C1 and C2 are mAh / cm respectively 2 . The initial discharge capacity C1 is the capacity when discharging at a constant current of 10 mA until the cell voltage reaches 2.0 V after assembling the evaluation half-cell. This discharge is hereinafter referred to as the initial discharge. The second discharge capacity C2 is the discharge capacity when charging at a constant current of 10 mA until the cell voltage reaches 0.01 V after the initial discharge and then discharging at a constant current of 10 mA until the cell voltage reaches 2.0 V.

[0142] Based on the value of the negative electrode doping capacity rate E in the evaluation half-cell, the battery stability was evaluated according to the following criteria. (Evaluation criteria for battery stability) A: The negative electrode doping capacity rate E is 82% or more.

[0143] B: The negative electrode doping capacity rate E is less than 82% and not less than 80%.

[0144] C: The negative electrode doping capacity rate E is less than 80%.

[0145] The negative electrode doping capacity rate E of the half cell for evaluation was 81%. According to the above criteria, the evaluation result of the battery stability of Example 1 was B.

[0146] (ix) Evaluation of productivity The time from when the electrode 1 starts to be pulled out from the supply roll 101 until the doped electrode 1A is wound onto the take-up roll 103 is defined as the working time T. The working time ratio TR represented by the following formula 5 was calculated. The unit of the working time ratio TR is %. (Formula 5) TR = (T / Tr1) × 100 Tr1 is the working time T in Example 1. Based on the value of the working time ratio TR, the productivity was evaluated according to the following criteria. (Evaluation criteria for productivity) A: The working time ratio TR is less than 80%. B: The working time ratio TR is not less than 80% and less than 110%. C: The working time ratio TR is not less than 110%. (Example 2) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed solution containing EC, EMC, and DMC in a volume ratio of 30:30:40.

[0147] In Example 2, the voltage after doping was 4.7V. The negative electrode potential was -2.4V. No Li deposition was observed on the doped electrode 1A. The DEC volume ratio was 3 vol%. The mass ratio X was 1.0%. The evaluation result of the battery stability was B. The evaluation result of the productivity was B.

[0148] In Example 2, compared with Example 1, the volume ratio of EMC in the solvent contained in the doping solution was large. Therefore, compared with Example 1, the DEC volume ratio was large and the voltage after doping was high. (Example 3) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC, EMC, and DMC in a volume ratio of 30:20:50.

[0149] In Example 3, the voltage after doping was 4.6 V. The negative electrode potential was -2.3 V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 1 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was B.

[0150] In Example 3, the volume ratio of EMC in the solvent of the doping solution was 50%. Therefore, a small amount of diethyl carbonate was generated in the doping solution, and the voltage after doping was slightly higher than that in Example 1. (Example 4) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC, EMC, and DMC in a volume ratio of 20:5:75.

[0151] In Example 4, the voltage after doping was 4.5 V. The negative electrode potential was -2.2 V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 0 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was B. (Example 5) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC and DMC in a volume ratio of 10:90.

[0152] In Example 5, the voltage after doping was 4.5 V. The negative electrode potential was -2.2 V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 0 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was B. (Example 6) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC and DMC in a volume ratio of 35:65.

[0153] In Example 6, the voltage after doping was 4.5V. The negative electrode potential was -2.2V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 0 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was B. (Example 7) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the time for continuous pre-doping was set to 40 hours.

[0154] In Example 7, the voltage after doping was 4.5V. The negative electrode potential was -2.2V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 0 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was B.

[0155] When the solvent contained in the doping solution was the same as that in Examples 1 and 7, even if the pre-doping time was extended compared to Example 1, the voltage after doping did not increase compared to Example 1. (Example 8) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the transport path of electrode 1 was a cleaning-omitted path.

[0156] In Example 8, the voltage after doping was 4.5V. The negative electrode potential was -2.2V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 0 vol%. The mass ratio X was 10%. The evaluation result of battery stability was A. The evaluation result of productivity was A.

[0157] In Example 8, by setting the transport path of electrode 1 as a cleaning-omitted path, the mass ratio X was improved, and the evaluation result of productivity was improved.

[0158] (Comparative Example 1) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC, EMC, and DMC in a volume ratio of 30:40:30.

[0159] In Comparative Example 1, the voltage after doping was 4.8 V. The negative electrode potential was -2.6 V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 10 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was B.

[0160] In Comparative Example 1, the content of DMC in the solvent contained in the doping solution was low. Therefore, the DEC volume ratio was large and the voltage after doping was high.

[0161] (Comparative Example 2) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC, EMC, and DMC in a volume ratio of 30:40:30. Also, the time for continuous predoping was set to 40 hours.

[0162] In Comparative Example 2, the voltage after doping was 5.0 V. The negative electrode potential was -2.8 V. Lithium deposition was observed on the doped electrode 1A. The DEC volume ratio was 17 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was C. The evaluation result of productivity was B.

[0163] In Comparative Example 2, the ratio of DMC in the solvent contained in the doping solution was low. Also, the time for predoping was long. Therefore, lithium was deposited on the doped electrode 1A. Also, the evaluation result of battery stability was poor. (Comparative Example 3) Basically, the doped electrode 1A was manufactured and evaluated in the same manner as in Example 1. However, the solvent contained in the doping solution was a mixed liquid containing EC, EMC, and DMC in a volume ratio of 30:40:30. Also, without reducing the mass ratio X compared to Example 1, the device current value and the conveyance speed were adjusted so that the current density became 1.22 mA / cm 2 ².

[0164] In Comparative Example 3, the voltage after doping was 0.9 V. The negative electrode potential was 0.05 V. Lithium deposition was not observed on the doped electrode 1A. The DEC volume ratio was 0 vol%. The mass ratio X was 1.0%. The evaluation result of battery stability was B. The evaluation result of productivity was C.

[0165] In Comparative Example 3, by reducing the current density, the negative electrode potential became a positive value, the reducibility with respect to the electrolytic solution was suppressed, and no increase in the DEC ratio was observed, but the evaluation result of productivity was extremely poor. <Other Embodiments> As described above, the embodiments of the present disclosure have been described. However, the present disclosure is not limited to the above-described embodiments and can be implemented with various modifications.

[0166] (1) The function possessed by one component in each of the above embodiments may be shared by a plurality of components, or the functions possessed by a plurality of components may be exhibited by one component. Also, a part of the configuration of each of the above embodiments may be omitted. Also, at least a part of the configuration of each of the above embodiments may be added to, replaced with, etc., the configuration of other of the above embodiments.

[0167] (2) In addition to the above-described method for manufacturing a doped electrode, the present disclosure can also be realized in various forms such as a manufacturing system for a doped electrode, a doped electrode, a secondary battery, and a method for manufacturing a secondary battery.

Description of Reference Numerals

[0168] 1…Electrode, 1A…Doped electrode, 3…Current collector, 5…Active material layer, 6…Active material layer forming section, 7…Active material layer non-forming section, 11…Electrode manufacturing system, 15…Electrolyte treatment tank, 17, 19, 21…Doping tanks, 23A, 23B, 23C…Washing tanks, 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, 207, 209, 211…Conveyor rollers, 101…Supply roll, 103…Take-up roll, 105…Support stand, 107…Circulating filtration unit, 109, 110, 111, 112, 113, 114…Power supplies, 117…Tab cleaner, 119…Recovery unit, 121…End sensor, 131…Upstream tank, 133…Downstream tank, 137, 139, 141, 143…Counter electrode units, 149, 151…Spaces, 161…Filter, 163…Pump, 165…Pipe, 213…Blower, 401…Frame body, 403…Bus bar, 407…Copper plate, 409…Lithium plate, 411…Mask, 501…Reference electrode unit, 503…Tab lead, 505…Reference lithium metal electrode, 507…Space

Claims

1. A method for manufacturing a doped electrode including an active material layer doped with an alkali metal, comprising: Conveying a strip-shaped electrode including an active material layer along a path passing through a doping bath containing a doping solution including alkali metal ions and an aprotic organic solvent and a counter electrode unit; Electrically connecting, in the doping bath, the counter electrode unit and the strip-shaped electrode including the active material layer through the doping solution; The content ratio of dimethyl carbonate in the aprotic organic solvent is 40 vol% or more and 95 vol% or less; When electrically connecting, in the doping bath, the counter electrode unit and the strip-shaped electrode including the active material layer through the doping solution, the potential of the strip-shaped electrode including the active material layer is -10 V or more and 0 V or less with reference to a reference lithium metal electrode; The reference lithium metal electrode is installed at a location within 7 mm from the strip-shaped electrode including the active material layer and outside the space where the counter electrode unit and the strip-shaped electrode including the active material layer face each other; A method for manufacturing a doped electrode.

2. A method for manufacturing a doped electrode including an active material layer doped with an alkali metal, comprising: Conveying a strip-shaped electrode including an active material layer along a path passing through a doping bath containing a doping solution including alkali metal ions and an aprotic organic solvent and a counter electrode unit; Electrically connecting, in the doping bath, the counter electrode unit and the strip-shaped electrode including the active material layer through the doping solution; The content ratio of dimethyl carbonate in the aprotic organic solvent is 40 vol% or more and 95 vol% or less; Drying the doped electrode taken out of the doping bath so as to contain 5 parts by mass or more and 40 parts by mass or less of the components of the doping solution with respect to 100 parts by mass of the active material layer; A method for manufacturing a doped electrode.

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