JP2017063069A - Method for manufacturing power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pre-dope a negative electrode active material of a power storage device with lithium ions uniformly and rapidly while keeping an adequate charge/discharge characteristic and a high energy density of the power storage device in a method for manufacturing a power storage device which needs the pre-doping of lithium ions.SOLUTION: A method for manufacturing a power storage device comprises: a first injection step for injecting a first electrolytic solution into the power storage device; a pre-doping step for executing a pre-doping in a state in which a negative electrode current collector is electrically connected with metallic lithium, and the negative electrode current collector and the metallic lithium are in contact with the first electrolytic solution; and a second injection step for injecting a second electrolytic solution which is higher than the first electrolytic solution in electrolyte concentration into the power storage device. Preferably the first electrolytic solution is 30 mPa S or less in viscosity, and the second electrolytic solution is 80 mPa S or higher in viscosity. More preferably, a mixed electrolytic solution which is a mixture of the first electrolytic solution and the second electrolytic solution is 60 mPa S or higher in viscosity.SELECTED DRAWING: Figure 11

Description

The present invention relates to a method for manufacturing an electricity storage device. The present invention particularly relates to a method of manufacturing a lithium ion capacitor.

  For some time, lithium ion capacitors have attracted attention as power storage devices that combine good charge / discharge characteristics and high energy density. The lithium ion capacitor is charged and discharged by a physical action by forming an electric double layer on the positive electrode side, and charged and discharged by a chemical reaction of lithium on the negative electrode side. In such a lithium ion capacitor, lithium ions are occluded (pre-doped) in advance in the negative electrode active material on the negative electrode side for the purpose of improving energy density.

  In the technical field, various techniques for enabling uniform and reliable pre-doping of lithium ions have been proposed for the purpose of improving energy density and charge / discharge characteristics.

  For example, micropores are formed in the positive and negative electrode current collectors of a lithium ion capacitor, and lithium ions eluted in the electrolyte during pre-doping migrate through the microholes in the stacking direction of each electrode plate. There is known a technique that enables this (see, for example, Patent Document 1). According to this, lithium ions can be pre-doped more uniformly and reliably in the negative electrode active material. In addition, the energy density and charge / discharge characteristics of the lithium ion capacitor can be improved.

  However, further improvements in the energy density and charge / discharge characteristics of lithium ion capacitors are required in this technical field.

Patent No. 4015993

  The present invention has been made to solve the above problems. That is, the present invention relates to a method for manufacturing an electricity storage device that requires lithium ion pre-doping, in which the negative electrode active material is uniformly and reliably pre-doped to improve energy density and charge / discharge characteristics of the electricity storage device. One object is to provide a device manufacturing method.

  The present invention relates to a method for manufacturing an electricity storage device that involves pre-doping lithium ions into a negative electrode active material provided on the surface of a negative electrode current collector, wherein the first electrolyte solution is injected into the electricity storage device. A pre-doping step of performing the pre-doping in a state in which the negative electrode current collector and the metal lithium are electrically connected and the negative electrode current collector and the metal lithium are in contact with the first electrolyte solution; A second injection step of injecting a second electrolyte solution into the electricity storage device, wherein the electrolyte concentration in the first electrolyte solution is lower than the electrolyte concentration in the second electrolyte solution, and did.

  According to the above configuration, lithium ions can be uniformly and surely pre-doped in the negative electrode active material, and the electrolyte concentration in the final electrolytic solution is a concentration suitable for achieving the desired performance as an electricity storage device. It can be. As a result, the energy density and charge / discharge characteristics of the electricity storage device can be improved.

It is typical sectional drawing which shows the lithium ion capacitor as an electrical storage device. It is II-II sectional drawing of FIG. It is III-III sectional drawing of FIG. It is IV-IV sectional drawing of FIG. It is a figure which shows the inner laminated body of FIG. It is a figure which shows a negative electrode unit. It is a figure which shows a positive electrode unit. It is a figure which expand | deploys and shows the outer side negative electrode unit which concerns on 1st Embodiment. It is sectional drawing which shows the electrical storage unit before the pre dope formed at the 2nd process of 1st Embodiment. It is sectional drawing which shows the lithium ion capacitor which the 6th process of 1st Embodiment was completed. It is a flowchart which compares the manufacturing method of the electrical storage device which concerns on a present Example, and the manufacturing method of the electrical storage device concerning a comparative example. It is a graph which compares the manufacturing method of the electrical storage device which concerns on a present Example, and the manufacturing method of the electrical storage device which concerns on a comparative example about the discharge capacity of an electrical storage device. It is a graph which compares the manufacturing method of the electrical storage device which concerns on a present Example, and the manufacturing method of the electrical storage device which concerns on a comparative example about the charge rate performance of an electrical storage device.

  Hereinafter, an embodiment relating to a method for manufacturing an electricity storage device according to the present invention (hereinafter, may be referred to as “this embodiment”) will be described. This embodiment is a method for manufacturing an electricity storage device that involves pre-doping lithium ions into a negative electrode active material provided on the surface of a negative electrode current collector. The power storage device is not particularly limited as long as it is a power storage device that requires pre-doping of lithium ions into the negative electrode active material provided on the surface of the negative electrode current collector. Specific examples of such an electricity storage device include a lithium ion capacitor.

Furthermore, this embodiment includes the steps (1) to (3) listed below.
(1) a first injection step of injecting a first electrolytic solution into the electricity storage device;
(2) a pre-doping step of performing the pre-doping in a state where the negative electrode current collector and metallic lithium are electrically connected and the negative electrode current collector and metallic lithium are in contact with the first electrolyte solution; And (3) a second pouring step of pouring the second electrolytic solution into the electricity storage device.

  In the first liquid injection step shown in (1) above, as described above, the first electrolytic solution containing a predetermined electrolyte (supporting salt) and solvent is injected into the electricity storage device. The first electrolytic solution is a non-aqueous solution having electrical conductivity (lithium ion conductivity), and is prepared, for example, by dissolving a lithium salt electrolyte in an organic solvent. The specific composition (lithium salt electrolyte and organic solvent) of the first electrolytic solution is not particularly limited as long as the desired performance as the electricity storage device can be exhibited.

Specific examples of the lithium salt electrolyte include lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenide (LiAsF ₆ ), and the like. A lithium salt can be mentioned.

  On the other hand, specific examples of the organic solvent include, for example, propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), formic acid. Mention may be made of ester solvents such as methyl (MF), methyl acetate (MA) and methyl propionate (MP). In addition, ether solvents such as γ-butylactone (γ-BL), diethoxyethane (DEE), 1,2-dimethoxyethane (DME), tetrahydrofuran (THF) and 1,3 dioxolane (DOL), and other solvents May be used in an organic solvent mixed and prepared in an ester solvent.

  In the pre-doping step shown in (2) above, as described above, the negative electrode current collector and metallic lithium are electrically connected, and the negative electrode current collector and metallic lithium are in contact with the first electrolytic solution. In this state, the pre-doping is performed. In the pre-doping step, metallic lithium is eluted as lithium ions in the electrolytic solution, and electrons released from the metallic lithium are conducted to the negative electrode current collector. The lithium ions eluted in the electrolytic solution migrate in the electrolytic solution, eventually reach the negative electrode active material, and are occluded (that is, pre-doped) by the negative electrode active material.

  In general, a power storage device such as a lithium ion capacitor has a configuration in which a power storage unit including an inner laminate and an outer negative electrode unit is immersed in an electrolytic solution. An internal laminated body is a laminated body which consists of the negative electrode unit and positive electrode unit which were laminated | stacked alternately on both sides of the separator. The negative electrode unit is constituted by a negative electrode active material provided on the surface of the negative electrode current collector, and the positive electrode unit is constituted by a positive electrode active material provided on the surface of the positive electrode current collector. The outer negative electrode unit includes at least an outer negative electrode current collector and metallic lithium. In the pre-doping step, for example, the negative electrode current collector and the metal lithium can be electrically connected by short-circuiting the negative electrode current collector of the negative electrode unit and the outer negative electrode current collector of the outer negative electrode unit.

  By the way, the electrolyte concentration in the 1st electrolyte injected in the 1st injection process shown to said (1) may be too low in order to achieve the desired performance as an electrical storage device.

  Therefore, according to the present embodiment, as described above, the second electrolytic solution is injected into the electricity storage device in the second injection step shown in (3) above. In addition, as described above, the electrolyte concentration in the first electrolytic solution is lower than the electrolyte concentration in the second electrolytic solution. In other words, the electrolyte concentration in the second electrolytic solution is higher than the electrolyte concentration in the first electrolytic solution.

  According to the above, even when the electrolyte concentration in the first electrolyte solution is too low to achieve the desired performance as the electricity storage device, the electrolyte concentration in the second electrolyte solution and the second electrolyte solution injected into the electricity storage device The amount of can be adjusted. As a result, the electrolyte concentration in the final electrolytic solution can be set to a concentration suitable for achieving the desired performance as the electricity storage device.

  As described above, according to the present embodiment, in the method of manufacturing an electricity storage device that requires lithium ion pre-doping, lithium ions can be uniformly and reliably pre-doped in the negative electrode active material, and the energy of the electricity storage device The density and charge / discharge characteristics can be improved.

  By the way, in recent years, in research on non-aqueous electrolytes, it has been discovered that increasing the electrolyte concentration increases the decomposition voltage of the electrolyte. However, in general, when the electrolyte and the organic solvent are the same, the higher the electrolyte concentration, the higher the viscosity of the electrolytic solution. Accordingly, if the electrolyte concentration is increased to increase the decomposition voltage of the electrolytic solution based on the above discovery, the viscosity of the electrolytic solution increases. Therefore, when the above discovery is applied to a lithium ion capacitor, it is difficult to pre-dope the present invention. Noticed. Therefore, as a result of earnest research, the inventor of the present invention has prepared an electrolytic solution concentration (viscosity) suitable for pre-doping and an electrolytic solution suitable as an electrolytic solution for an electrical storage device in a method for manufacturing an electrical storage device such as a lithium ion capacitor having the above-described configuration It was found that the concentration (viscosity) was different. Specifically, in the present embodiment, the viscosity of the first electrolytic solution is 30 mPa · S or less. More preferably, the viscosity of the first electrolytic solution is 27 mPa · S or less.

  According to the above, at the time of pre-doping, not only can the air existing between each component (for example, the positive electrode unit, the negative electrode unit, and the separator) constituting the power storage unit be easily replaced by the electrolytic solution, The migration of lithium ions in the liquid can be facilitated, so that the lithium ions can reach the negative electrode active material earlier and can be more uniformly occluded in the negative electrode active material. That is, pre-doping can be performed uniformly and reliably.

  The method for adjusting the viscosity of the first electrolytic solution is not particularly limited. For example, the viscosity of the first electrolyte solution can be adjusted by the combination of the selected electrolyte and organic solvent and / or the electrolyte concentration in the electrolyte solution.

  As described above, generally, when the electrolyte and the organic solvent are the same, the higher the electrolyte concentration, the higher the viscosity of the electrolytic solution. That is, since the electrolyte concentration in the second electrolyte solution is higher than the electrolyte concentration in the first electrolyte solution, the viscosity of the second electrolyte solution is often higher than the viscosity of the first electrolyte solution. Therefore, in a preferred embodiment of the present invention, the viscosity of the second electrolytic solution is 80 mPa · S or more, more preferably 90 mPa · S or more.

  In addition, as described above, by pouring the second electrolytic solution, the electrolyte concentration in the final electrolytic solution can be set to a concentration suitable for achieving desired performance as an electricity storage device. That is, the final electrolyte in the electricity storage device manufactured according to this embodiment often has the same viscosity as the electrolyte in the electricity storage device according to the related art that achieves the desired performance as the electricity storage device. Therefore, in another preferred embodiment of the present embodiment, the viscosity of the mixed electrolytic solution that is a mixture of the first electrolytic solution and the second electrolytic solution is 60 mPa · S or more, more preferably 70 mPa · S or more. It is.

  Other features and attendant advantages of this embodiment will be readily understood from the description of each embodiment described with reference to the following drawings.

[First Embodiment]
(Configuration of electricity storage device)
Hereinafter, the configuration of the electricity storage device manufactured by the method for manufacturing the electricity storage device according to the first embodiment of the present invention (hereinafter sometimes referred to as “first method”) will be described. FIG. 1 is a schematic cross-sectional view showing a lithium ion capacitor 1 as an electricity storage device manufactured by the first method. As shown in FIG. 1, the lithium ion capacitor 1 includes a bag-like case 6, a nonaqueous electrolyte solution 5 filled in the case 6, and a power storage unit 2 immersed in the nonaqueous electrolyte solution 5. Prepare. In the following description, when each configuration is described with a direction, the vertical direction in FIG. 1 is defined as the height direction, and the horizontal direction is defined as the width direction. Further, a direction perpendicular to the paper surface of FIG. 1, that is, a direction perpendicular to the height direction and the width direction is defined as the front-rear direction.

  The case 6 is configured so that the nonaqueous electrolytic solution 5 and the power storage unit 2 can be hermetically accommodated. In this example, the case 6 is a soft case obtained by heat sealing (welding) a so-called “aluminum laminate film” formed by laminating aluminum and polypropylene (PP). More specifically, the case 6 can be formed in a rectangular bag shape by stacking two rectangular aluminum laminate films and joining the four side edges by welding.

  A positive terminal 61 and a negative terminal 62 are attached to the case 6. The positive electrode terminal 61 and the negative electrode terminal 62 are attached to the case 6 so that the tip portion protrudes from the case 6 while maintaining the sealed state in the case 6. The power storage unit 2 in the case 6 is electrically connected to the base ends of these terminals 61 and 62. Therefore, by connecting an electric load between the positive electrode terminal 61 and the negative electrode terminal 62, the electric energy generated in the power storage unit 2 can be taken out.

The non-aqueous electrolyte 5 is a non-aqueous solution having electrical conductivity (lithium ion conductivity), and can be prepared, for example, by dissolving a lithium salt electrolyte in an organic solvent as described above. In this example, lithium hexafluorophosphate (LiPF ₆ ) was employed as the lithium salt electrolyte, and diethyl carbonate (DEC) was employed as the organic solvent. However, as described above, the lithium salt electrolyte and the organic solvent are not limited to these.

  2 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a sectional view taken along line III-III in FIG. 1, and FIG. 4 is a sectional view taken along line IV-IV in FIG. 2 and 3 are cross-sectional views of the lithium ion capacitor 1 cut along a plane perpendicular to the width direction, and FIG. 4 is a cross-sectional view of the lithium ion capacitor 1 cut along a plane perpendicular to the height direction. is there. As described above, the power storage unit 2 includes the inner laminated body 3 and the outer negative electrode unit 4 (see FIGS. 2 to 4).

  FIG. 5 is a cross-sectional view showing only the inner laminate 3 shown in FIG. As shown in FIG. 5, the inner laminate 3 includes a plurality of negative electrode units 31, a plurality of positive electrode units 32, and a separator 33. A plurality of negative electrode units 31 and a plurality of positive electrode units 32 are alternately stacked along the front-rear direction with the separator 33 interposed therebetween. In this example, the inner laminate 3 has a rectangular parallelepiped shape. Therefore, the inner laminate 3 has both side surfaces in the stacking direction (front-rear direction) of the negative electrode unit 31 and the positive electrode unit 32 and four side surfaces formed along the stacking direction.

  6A and 6B are views showing the negative electrode unit 31, wherein FIG. 6A is a front view of the negative electrode unit 31 viewed from the front-rear direction, and FIG. 6B is a side view of the negative electrode unit 31 viewed from the width direction. As shown in FIG. 6, the negative electrode unit 31 includes a sheet-like negative electrode current collector 311 and a negative electrode active material 312. The negative electrode current collector 311 has a substantially rectangular shape when viewed from the front. A negative electrode lead portion A is formed on the negative electrode current collector 311 so as to protrude from the upper left portion when viewed from the front. The negative electrode current collector 311 is formed of a material (good conductor) having good conductivity. In this example, a copper foil was used as the negative electrode current collector 311.

  A negative electrode active material 312 is applied to both surfaces of the negative electrode current collector 311. The negative electrode active material 312 is not applied to the negative electrode lead portion A. The negative electrode active material 312 is made of a material that can occlude and release lithium ions. Specifically, the negative electrode active material 312 can be made of, for example, graphite, hard carbon, soft carbon, CNT (carbon nanotube), or the like. However, the material constituting the negative electrode active material 312 is not particularly limited as long as the function described above can be achieved. In this example, crystalline carbon is employed as the negative electrode active material 312.

  7A and 7B are diagrams showing the positive electrode unit 32, where FIG. 7A is a front view of the positive electrode unit 32 viewed from the front-rear direction, and FIG. 7B is a side view of the positive electrode unit 32 viewed from the width direction. As shown in FIG. 7, the positive electrode unit 32 includes a sheet-like positive electrode current collector 321 and a positive electrode active material 322. The positive electrode current collector 321 has a substantially rectangular shape when viewed from the front. A positive electrode lead portion B is formed on the positive electrode current collector 321 so as to protrude from the upper right portion when viewed from the front. The positive electrode current collector 321 is formed of a material having good conductivity (good conductor). In this example, an aluminum foil was used as the positive electrode current collector 321.

  A positive electrode active material 322 is applied to both surfaces of the positive electrode current collector 321. The positive electrode active material 322 is not applied to the positive electrode lead portion B. The positive electrode active material 322 is made of a material that can reversibly carry lithium ions and / or electrolyte anions. The positive electrode active material 322 can be composed of, for example, activated carbon. However, the material forming the positive electrode active material 322 is not particularly limited as long as the function described above can be achieved. In this example, activated carbon is employed as the positive electrode active material 322.

  As shown in FIG. 5, the separator 33 of the inner laminate 3 includes a plurality of inner separators 331, a pair of end separators 332, and one side separator 333. The negative electrode units 31 and the positive electrode units 32 are alternately stacked along the front-rear direction with a plurality of internal separators 331 interposed therebetween, and a pair of end separators 332 are disposed on both end surfaces of the inner stacked body 3 in the stacking direction (front-rear direction). Is done. Further, the side separator 333 is disposed along the stacking direction so as to form a part of the side surface of the inner laminate 3 (the left side surface in FIG. 5).

  Further, as shown in FIG. 5, the left end portions in the width direction of all the internal separators 331 and the pair of end separators 332 are connected to the side separator 333. Specifically, the gap formed at the left end of each of the adjacent end separator 332 and the internal separator 331 and the gap formed at the left end of each of the two adjacent internal separators 331 are All the internal separators 331 and the pair of end separators 332 are connected to the side separators 333 so as to be closed by the partial separators 333.

  Accordingly, a space in which one end (left end in FIG. 5) is closed by the side separator 333 is formed in the separator 33 along the stacking direction (front-rear direction). The negative electrode unit 31 or the positive electrode unit 32 is disposed in each space. In addition, the positive electrode unit 32 is arrange | positioned in the space between the edge part separator 332 and the internal separator 331 adjacent to it, ie, the space located in the both ends in the lamination direction.

  The separator 33 is provided to prevent contact between the negative electrode unit 31 and the positive electrode unit 32. As the separator 33, a porous substrate is preferably used. Specifically, for example, a porous film substrate formed of polyolefin such as polyethylene (PE) and polypropylene (PP) can be used as the separator 33. However, the material constituting the separator 33 is not particularly limited as long as the function described above can be achieved. In this example, a polypropylene (PP) porous film was adopted as the separator 33.

  As shown in FIG. 4, the outer negative electrode unit 4 is provided so as to wrap the inner laminate 3. FIG. 8 is a developed view of the outer negative electrode unit 4 enclosing the inner laminate 3, (a) is a front view, and (b) is a side view. As shown in FIG. 8, the outer negative electrode unit 4 includes a sheet-like outer negative electrode current collector 41 and an outer negative electrode active material 42. The outer negative electrode current collector 41 has a horizontally long rectangular shape in which a rectangular first portion 41a, a second portion 41b, and a third portion 41c are connected in the horizontal direction in this order.

  A negative electrode lead portion A is formed in the upper left portion of the first portion 41a and the upper right portion of the third portion 41c. The first portion 41 a and the third portion 41 c have the same size and shape as the negative electrode current collector 311 of the negative electrode unit 31. The outer negative electrode current collector 41 is also formed of a good conductor. The material constituting the outer negative electrode current collector 41 may be the same material as the negative electrode current collector 311, or may be a material different from the negative electrode current collector 311.

  The outer negative electrode active material 42 is applied to one surface of the first portion 41a and the third portion 41c facing the same side. The outer negative electrode active material 42 may be the same material as the negative electrode active material 312 applied to the negative electrode current collector 311, or may be a material different from the negative electrode active material 312. On the other hand, the outer negative electrode active material 42 is not applied to the other surface of the first portion 41a and the third portion 41c facing the same side, the second portion 41b, and the negative electrode lead portion A.

  Further, on the surface of the second portion 41b facing the same side as the one surface (the surface coated with the outer negative electrode active material 42) of the first portion 41a and the third portion 41c, the lithium ion capacitor 1 The metallic lithium 43 used in the pre-doping step in the manufacturing method is attached (see the blackened portion in FIG. 8). Since the metal lithium 43 is eluted as lithium ions in the non-aqueous electrolyte 5 in the pre-doping process of the lithium ion capacitor 1, when the manufacture of the lithium ion capacitor 1 is completed, strictly speaking, when the pre-doping process is completed, Disappeared.

  As shown in FIG. 4, the outer negative electrode unit 4 faces both end surfaces of the inner laminate 3 in the lamination direction (front-rear direction) of the negative electrode unit 31 and the positive electrode unit 32 and the left side surface of the inner laminate 3 in the width direction. Thus, the inner laminated body 3 is covered. In this case, the outer negative electrode active material 42 applied to the first portion 41 a of the outer negative electrode current collector 41 is in face-to-face contact with the end separator 332 disposed on the front end surface of the inner laminate 3. On the other hand, the outer negative electrode active material 42 applied to the third portion 41 c of the outer negative electrode current collector 41 is brought into face contact with the end separator 332 disposed on the rear end surface of the inner laminate 3. Further, the second portion 41 b of the outer negative electrode current collector 41 is disposed facing the side separator 333 provided on the left side surface in the width direction of the inner laminate 3.

  The negative electrode lead part A provided in the negative electrode current collector 311 of each negative electrode unit 31 of the inner laminate 3 and the two negative electrode lead parts A provided in the outer negative electrode current collector 41 of the outer negative electrode unit 4 are shown in FIG. As shown, they are connected by a negative electrode side conductive connecting member 25 such as a lead wire. The negative electrode side conductive connection member 25 is electrically connected to the negative electrode terminal 62. Moreover, as shown in FIG. 3, the positive electrode lead part B provided in the positive electrode current collector 321 of each positive electrode unit 32 of the inner laminate 3 is connected by a positive electrode side conductive connection member 26 such as a lead wire. . The positive electrode side conductive connection member 26 is electrically connected to the positive electrode terminal 61.

  Note that the negative electrode lead portion A may be configured to be directly connected to the negative electrode terminal 62 by bonding, rivet fastening, or the like without using the negative electrode side conductive connection member 25. Similarly, the positive electrode lead portion B may be configured to be directly connected to the positive electrode terminal 61 by bonding, rivet fastening, or the like without using the positive electrode side conductive connection member 26.

  As will be described in detail later, the negative electrode active material 312 of each negative electrode unit 31 and the outer negative electrode active material 42 of the outer negative electrode unit 4 are preliminarily occluded (pre-doped) in the pre-doping step.

  In the lithium ion capacitor 1 having the above-described configuration, electric energy is charged and discharged by the electrochemical reaction of lithium ions in the negative electrode unit 31 and the outer negative electrode unit 4, and in the positive electrode unit 32, lithium ions or Electric energy is charged and discharged by physical adsorption / desorption of anions.

  The lithium ion capacitor 1 is only one specific example of an electricity storage device to which the method for producing an electricity storage device according to the present invention can be applied. That is, it goes without saying that the method for manufacturing an electricity storage device according to the present invention can be applied to a wide variety of electricity storage devices that require lithium ion pre-doping.

(Production method)
Next, the manufacturing method of the lithium ion capacitor 1 having the above-described configuration will be described in detail below.

(First step)
First, the inner laminated body 3 as shown in FIG. 5 is formed. That is, the negative electrode unit 31 and the positive electrode unit 32 are alternately stacked with the internal separator 331 interposed therebetween. In addition, a pair of end separators 332 are disposed on both end faces of the laminate of the negative electrode unit 31 and the positive electrode unit 32, and the side separator 333 forms the left side surface of the inner laminate 3 in FIG. The side separator 333 is disposed along the stacking direction. In this way, the internal laminate 3 is formed in which the pair of end separators 332 are disposed on both end surfaces in the stacking direction, and the side separator 333 is disposed on the left side surface.

(Second step)
Next, the outer negative electrode current collector 41 is prepared. Then, the outer negative electrode active material 42 is applied to one surface of the first portion 41a and the third portion 41c of the prepared outer negative electrode current collector 41, and metal lithium 43 is attached to one surface of the second portion 41b. By attaching, the outer negative electrode unit 4 is formed. In this case, it is preferable that the metal lithium 43 is pressure-bonded to the second portion 41b so that the metal lithium 43 reliably contacts the second portion 41b of the outer negative electrode current collector 41.

  Next, the inner laminate 3 is covered with the outer negative electrode unit 4. In this case, the first separator 41a of the outer negative electrode current collector 41 is applied to the end separator 332 disposed on the front end surface in the stacking direction (front-rear direction) of the negative electrode unit 31 and the positive electrode unit 32 in the inner stacked body 3. The outer negative electrode active material 42 that is coated on the third portion 41c of the outer negative electrode current collector 41 faces the end separator 332 disposed on the rear end surface in the stacking direction. In the outer negative electrode current collector 41, the metal lithium 43 pressed against the second portion 41 b of the outer negative electrode current collector 41 faces the side separator 333 disposed on one side surface of the inner laminate 3. The inner laminate 3 is covered. Thereby, the power storage unit 2 before pre-doping is formed.

  FIG. 9 is a diagram showing the power storage unit 2 before pre-doping formed in the second step. As shown in FIG. 9, the metal lithium 43 provided in the second portion 41 b of the outer negative electrode current collector 41 extends over the entire area in the stacking direction (front-rear direction) of the negative electrode unit 31 and the positive electrode unit 32 in the inner stacked body 3. The side separator 333 is arranged to face each other.

(Third step)
Next, the negative electrode current collector 311 and the negative electrode lead portion A of the outer negative electrode current collector 41 are connected by the negative electrode side conductive connecting member 25, so that all the negative electrode current collectors 311 in the power storage unit 2 and the outer negative electrode current collector 41 are connected. The electric body 41 is electrically connected. In addition, by connecting the positive electrode lead portion B of the positive electrode current collector 321 with the positive electrode side conductive connection member 26, all the positive electrode current collectors 321 in the power storage unit 2 are electrically connected.

  Subsequently, two rectangular aluminum laminate films were prepared, these were overlaid, and one of the four sides of each laminated film was sealed by welding to open one side. A bag-like case 6 is formed. The power storage unit 2 is put into the case 6 from the opening of the case 6. Then, the negative electrode side conductive connection member 25 is connected to the negative electrode terminal 62, and the positive electrode side conductive connection member 26 is connected to the positive electrode terminal 61.

(4th process)
Thereafter, the nonaqueous electrolytic solution 5 is filled in the case 6. However, in the first method, the first electrolyte solution 51 having a predetermined viscosity is first injected instead of filling (injecting) the nonaqueous electrolyte solution 5 having the final electrolyte concentration and viscosity at once. . Specifically, first electrolytic solution 51 having a viscosity of 30 mPa · S or less is first poured. This 4th process corresponds to the 1st pouring process in the manufacturing method of the electrical storage device concerning the present invention.

  As described above, the first electrolytic solution 51 has a sufficiently low viscosity. Therefore, the air present between the constituent elements (for example, the negative electrode unit 31, the positive electrode unit 32, the separator 33, and the like) constituting the power storage unit 2 can be easily replaced by the first electrolytic solution 51.

(5th process)
The storage unit 2 is immersed in the first electrolyte solution 51 by filling the case 6 with the first electrolyte solution 51 in the fourth step. Thereby, the metallic lithium 43 attached to the second portion 41 b of the outer negative electrode current collector 41 of the power storage unit 2 is also immersed in the first electrolytic solution 51. The metallic lithium 43 is short-circuited to each negative electrode current collector 311 via the outer negative electrode current collector 41 and the negative electrode side conductive connecting member 25. Accordingly, the metal lithium 43 emits electrons to the outer negative electrode current collector 41 and each negative electrode current collector 311 and is eluted as lithium ions in the first electrolytic solution 51.

  The lithium ions eluted in the first electrolyte 51 migrate on the surface of the outer negative electrode unit 4 in the power storage unit 2 along the width direction, and pass through the side separator 333 to pass through the surface of each negative electrode unit 31. Run along the width direction. Then, lithium ions are occluded in the outer negative electrode active material 42 of the outer negative electrode unit 4 and the negative electrode active material 312 of each negative electrode unit 31. In this way, pre-doping is completed. When the pre-doping is completed, the metallic lithium 43 provided in the outer negative electrode unit 4 disappears as shown in FIG. This fifth step corresponds to a pre-doping step in the method for manufacturing an electricity storage device according to the present invention.

  In addition, as described in the description regarding the fourth step, the first electrolytic solution 51 has a sufficiently low viscosity. Therefore, migration of lithium ions in the first electrolytic solution 51 becomes easier, so that the pre-doping in the fifth step can be performed more uniformly and rapidly.

(Sixth step)
When the pre-doping in the fifth step is completed, the second electrolytic solution 52 is further injected into the case 6. The second electrolytic solution 52 has a higher electrolyte concentration than the first electrolytic solution 51. This sixth step corresponds to the second pouring step in the method for manufacturing an electricity storage device according to the present invention.

  As described above, the second electrolytic solution 52 has a higher electrolyte concentration than the first electrolytic solution 51. Therefore, even if the electrolyte concentration in the first electrolyte solution 51 injected in the fourth step is too low to achieve the desired performance as the electricity storage device, the electrolyte concentration and the second electrolysis in the second electrolyte solution 52 By adjusting the amount of the liquid 52, the electrolyte concentration in the final electrolytic solution 5 can be set to a concentration suitable for the lithium ion capacitor 1 to achieve a desired performance as an electricity storage device. That is, it is possible to maintain good charge / discharge characteristics and a high energy density as an electricity storage device.

(Seventh step)
After injecting the second electrolytic solution 52 in the sixth step, the positive electrode terminal 61 and the negative electrode terminal 62 are sandwiched in the opening of the case 6, and in this state, the opening is sealed by welding. FIG. 10 shows the lithium ion capacitor 1 in which the seventh step has been completed. The seventh step is for the purpose of sufficiently replacing the air existing between the constituent elements constituting the power storage unit 2 (for example, the negative electrode unit 31, the positive electrode unit 32, the separator 33, etc.) with the electrolytic solution 5 and the like. Before the case 6 is sealed, a so-called “degas” (degas) step may be performed.

(8th step)
The power storage unit 2 completed as described above is generally charged before use (initial charge). In this case, after completion of the seventh step, initial charging is performed under predetermined charging conditions. In addition, a so-called “degas” (degas) step may be performed after the initial charge in the eighth step for the purpose of sufficiently replacing the gas generated by the initial charge with the electrolyte 5. .

  As described above, according to the first method, the first electrolytic solution 51 having a predetermined viscosity is first injected in the fourth step (first injection step). Therefore, not only can the air present between the components constituting the power storage unit 2 be easily replaced by the first electrolytic solution 51, but also the migration of lithium ions in the first electrolytic solution 51 is easier. Therefore, the pre-doping in the fifth step (pre-doping step) can be performed more uniformly and rapidly.

  In addition, according to the first method, the second electrolytic solution 52 having an electrolyte concentration higher than that of the first electrolytic solution 51 is added in the sixth step (second injection step). Therefore, even if the electrolyte concentration in the first electrolyte solution 51 is too low, the electrolyte concentration in the final electrolyte solution 5 is set to a suitable concentration by adjusting the electrolyte concentration and the additional amount of the second electrolyte solution 52. Thus, it is possible to maintain good charge / discharge characteristics and high energy density as an electricity storage device.

  By the way, as described above, generally, when the electrolyte and the organic solvent are the same, the higher the electrolyte concentration, the higher the viscosity of the electrolytic solution. Since the electrolyte concentration in the second electrolyte solution 52 is higher than the electrolyte concentration in the first electrolyte solution 51, the viscosity of the second electrolyte solution 52 is often higher than the viscosity of the first electrolyte solution 51. In another embodiment of the present invention, the viscosity of the second electrolytic solution 52 is 80 mPa · S or more, more preferably 90 mPa · S or more.

  Furthermore, as described above, the final electrolytic solution in which the electrolyte concentration is adjusted to a suitable concentration in this way is the same as the electrolytic solution in the power storage device according to the related art that achieves the desired performance as the power storage device. Often has a viscosity. In another embodiment of the present invention, the final mixed electrolyte, which is a mixture of the first electrolyte 51 and the second electrolyte 52, has a viscosity of 60 mPa · S or more, more preferably 70 mPa · S. That's it.

  In addition, the manufacturing method of the electrical storage device 2 demonstrated above is an example to the last, and the manufacturing method of an electrical storage device is not limited above as long as application of the manufacturing method of the electrical storage device which concerns on this invention is not prevented.

  One embodiment (hereinafter referred to as “this embodiment”) of a method for manufacturing an electricity storage device according to the present invention will be described in detail below. In this example, the manufacturing method according to this example and the comparative example (conventional example) with respect to the lithium ion capacitor 1 described in the description related to the method for manufacturing the electricity storage device (first method) according to the first embodiment of the present invention described above. The manufacturing method according to (Technology) and the results applied respectively were compared.

(Composition of electrolyte)
The compositions of the electrolytic solutions used in the manufacturing method according to this example and the manufacturing method according to the comparative example are listed in Table 1 below. As shown in Table 1, in the manufacturing method according to this example, the electrolytic solution was injected separately into a first electrolytic solution having a relatively low viscosity and a second electrolytic solution having a relatively high electrolyte concentration. did. On the other hand, in the manufacturing method according to the comparative example, the third electrolyte solution having the same viscosity and electrolyte concentration as the conventional one was injected at once without dividing the electrolyte.

(Manufacturing process)
Next, differences in manufacturing steps between the manufacturing method according to the present embodiment and the manufacturing method according to the comparative example will be described with reference to FIG. In the flowchart shown in FIG. 11, only the fourth and subsequent steps in which the difference between the manufacturing method according to the present embodiment and the manufacturing method according to the comparative example appears among the first to eighth steps described above. Showed.

  As shown in FIG. 11, in the fourth step, in the manufacturing method according to the comparative example, the third electrolytic solution having an electrolyte concentration (3.3M) and a viscosity (72.4 mPa · S) as a final electrolytic solution. Was filled (injected) into the case 6 at once. On the other hand, in the manufacturing method according to this example, the case 6 was filled with only the first electrolyte solution (50 mL) having a relatively low electrolyte concentration (1.0 M) and viscosity (26.6 mPa · S). .

  Next, the manufacturing method according to the present example and the manufacturing method according to the comparative example are the same in that pre-doping is performed in the fifth step. However, in the manufacturing method according to the present example, since the viscosity of the electrolyte solution in which lithium ions migrate during the pre-doping is lower, the pre-doping is quicker and faster than the manufacturing method according to the comparative example. proceed. In this example, pre-doping was performed for 8 days at a temperature of 25 ° C. in both the manufacturing method according to this example and the manufacturing method according to the comparative example.

  Next, in the sixth step, in the manufacturing method according to the present example, the second electrolytic solution (350 mL) having a relatively high electrolyte concentration (3.6 M) and viscosity (94.6 mPa · S) is applied to case 6. Filled. Thereby, the mixture of 1st electrolyte solution and 2nd electrolyte solution becomes the same composition as the 3rd electrolyte solution used in the comparative example. On the other hand, in the manufacturing method according to the comparative example, as described above, since all the electrolyte solution (third electrolyte solution) was already filled in the fourth step, the electrolyte solution was not added in the sixth step.

  In the seventh step, in any of the manufacturing method according to the present embodiment and the manufacturing method according to the comparative example, after the degas treatment is performed under a predetermined condition, the opening portion of the case 6 is sealed by welding. . Furthermore, in the eighth step, initial charging was performed under predetermined conditions in both the manufacturing method according to the present example and the manufacturing method according to the comparative example.

(Evaluation of battery performance)
Various battery performances of the electricity storage device according to this example and the electricity storage device according to the comparative example manufactured as described above were compared. Specifically, the electricity storage device according to this example was compared with the electricity storage device according to the comparative example with respect to the doping rate of lithium ions into the negative electrode active material, the discharge capacity, and the charge rate performance. The outline of each evaluation method is listed below.

(1) Doping rate of lithium ion into negative electrode active material The internal laminated body of the electricity storage device at the time of completion of pre-doping was taken out and punched out with a punch to produce a coin cell having a negative electrode as a working electrode and metallic lithium as a counter electrode. The coin cell was connected to a charging / discharging device, and the amount of energy that could be taken out when a current was passed in the direction in which lithium ions were desorbed from the negative electrode was measured as the actual amount of energy. Next, in the coin cell, the lithium ions were sufficiently doped by flowing current in the direction in which the lithium ions were occluded in the negative electrode. Then, using this fully doped coin cell, the amount of energy that could be extracted when a current was passed in the direction in which lithium ions were desorbed from the negative electrode was measured as the reference energy amount. The ratio of the actually measured energy amount to the reference energy amount was calculated as the doping rate of the lithium ion negative electrode active material.

(2) Discharge capacity Discharge when each power storage device is connected to a charger / discharger and charged at a constant current of 1A at 3.8V for 2 hours and then discharged at a constant current of 1A. Each capacity (Ah) was measured.

(3) Charging rate performance Each storage device is connected to a charger / discharger, charged at a constant current of 1A, then discharged at a constant current of 1A, and a constant of 180A. The discharge capacity (Ah) when discharging at a constant current of 1 A after charging with current was measured. The latter ratio with respect to the former was calculated as the charge rate performance.

(Battery performance evaluation results)
The evaluation results of various battery performances of the electricity storage device according to this example and the electricity storage device according to the comparative example measured as described above are listed in Table 2 below.

(1) Doping rate of negative electrode active material of lithium ion As is clear from Table 2, under the pre-doping condition (25 ° C. × 8 days) in the fifth step described above, the electricity storage device according to the comparative example is 0% The doping rate was exhibited. This is because the migration rate of lithium ions in the electrolyte solution having a high viscosity as in the third electrolyte solution described above is extremely low, and therefore, in the pre-dope condition (25 ° C. × 8 days) in the fifth step described above, the metal It is considered that lithium ions eluted from the lithium 43 could not substantially reach the negative electrode active material.

  In contrast, the electricity storage device according to this example exhibited a doping rate of 76%. This is because, in the electricity storage device according to this example, since the pre-doping was performed in the first electrolytic solution having a relatively low viscosity, the migration speed of lithium ions in the electrolytic solution was high, and as a result, many It is considered that lithium ions were occluded by the negative electrode active material 312.

(2) Discharge capacity As is clear from the graphs shown in Table 2 and FIG. 12, the electricity storage device according to this example is related to the comparative example, reflecting the high doping rate verified by the above (1). It exhibited a high discharge capacity that was more than twice that of the electricity storage device.

(3) Charging rate performance As is clear from the graphs shown in Table 2 and FIG. 13, the power storage device according to this example is extremely high in charge rate performance as compared with the power storage device according to the comparative example. Demonstrated performance. This also means that in the method for manufacturing an electricity storage device according to the present invention, the electrolyte solution is injected in two stages, so that migration of lithium ions in the electrolyte solution and occlusion into the negative electrode active material in the pre-doping step are smoothly performed. It is thought to have progressed.

  As described above, according to the method for manufacturing an electricity storage device according to this example, the pre-doping of the negative electrode active material of lithium ions can be more uniformly and reliably performed, and the energy density and charge / discharge characteristics of the electricity storage device can be improved. I was able to improve. The method for producing an electricity storage device according to this example is particularly suitable for producing an electricity storage device having a high electrolyte concentration in the electrolytic solution and a high viscosity of the electrolytic solution.

  As mentioned above, although embodiment of this invention was described, this invention should not be limited to the embodiment or Example mentioned above. For example, in each of the above-described embodiments, the example in which the shape of the inner laminated body is a rectangular parallelepiped shape has been described, but it may be a polygonal column shape or a cylindrical shape. That is, there is no limitation on the shape of the inner laminate. Moreover, in the said embodiment etc., although the lithium ion capacitor was illustrated as an electrical storage device, this invention is applicable also to the lithium battery by which lithium ion was pre-doped. Thus, the present invention can be modified without departing from the gist thereof.

DESCRIPTION OF SYMBOLS 1 ... Lithium ion capacitor (electric storage device), 2 ... Electric storage unit, 3, 3 ', 3 "... Internal laminated body, 31 ... Negative electrode unit, 311 ... Negative electrode collector, 312 ... Negative electrode active material, 32 ... Positive electrode unit, 321 ... Positive electrode current collector, 322 ... Positive electrode active material, 33, 33 ', 33 "... Separator, 331, 331', 331" ... Internal separator, 332, 332 ', 332 "... End separator, 333 ... Side part Separator, 333D ... lower side separator, 333L ... left side separator, 333R ... right side separator, 4 ... outer negative electrode unit, 41 ... outer negative electrode current collector, 41a ... first part, 41b ... second part, 41c ... first 3 parts, 41d ... 4th part, 41e ... 5th part, 42 ... outside negative electrode active material, 43 ... metallic lithium, 5 ... non-aqueous electrolyte, 51 ... 1st electrolyte, 52 ... 2nd electrolysis , And 6 ... case.

Claims (3)

A method for producing an electricity storage device with pre-doping of lithium ions into a negative electrode active material provided on the surface of a negative electrode current collector,
A first injection step of injecting a first electrolyte into the electricity storage device;
A pre-doping step of performing the pre-doping in a state where the negative electrode current collector and the metal lithium are electrically connected and the negative electrode current collector and the metal lithium are in contact with the first electrolyte solution;
A second pouring step of pouring a second electrolyte into the electricity storage device;
Including
The electrolyte concentration in the first electrolyte solution is lower than the electrolyte concentration in the second electrolyte solution,
A method for manufacturing an electricity storage device. It is a manufacturing method of the electrical storage device according to claim 1,
The first electrolyte solution has a viscosity of 30 mPa · S or less,
The viscosity of the second electrolytic solution is 80 mPa · S or more,
A method for manufacturing an electricity storage device. It is a manufacturing method of the electrical storage device according to claim 2,
The viscosity of the mixed electrolyte which is a mixture of the first electrolyte and the second electrolyte is 60 mPa · S or more,
A method for manufacturing an electricity storage device.

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