JP2018006369A - Method for manufacturing electrode for power storage device, and method for manufacturing power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time required for pre-doping without decreasing the effective area of an electrode.SOLUTION: A method for manufacturing an electrode for a power storage device comprises: a take-up step for taking up, by winding around a reel 21, a belt-shaped structure arranged by putting lithium foil on each or one face of an electrode with an active material layer provided on each face of a current collector; a holding step for putting the reel 21 with the belt-shaped structure wound therearound in a container containing a driving electrolyte solution, and holding the container at a predetermined temperature; a drying step for drying the container after having been held at the predetermined temperature, in a predetermined atmosphere; and a take-out step for taking the reel from inside the container and taking the electrode from the reel.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing an electrode for an electricity storage device and a method for producing an electricity storage device using a carbon material in which activated carbon is used for a positive electrode and lithium is pre-doped for a negative electrode.

  An electric double layer capacitor can be rapidly charged and discharged, has a long life, but has a small storage capacity. Secondary batteries have a large storage capacity, but rapid charge / discharge is difficult. Therefore, lithium ion capacitors are known as power storage devices that compensate for the shortcomings of electric double layer capacitors and secondary batteries. A lithium ion capacitor is an asymmetric capacitor using a carbon material pre-doped with activated carbon for a positive electrode and lithium for a negative electrode.

  In Patent Document 1, a wound power storage unit formed by winding a strip in which a negative electrode, a separator, and a positive electrode are overlapped from one end in the length direction is accommodated in a container, and two lithium metals are provided for the negative electrode. An electrochemical device in which the arrangement position of the sheet is adjusted is disclosed. Thus, by adjusting the arrangement positions of the two lithium metal sheets with respect to the negative electrode, it is possible to efficiently dope lithium ions into the entire negative electrode.

JP 2012-114161 A

  However, the electrochemical device described in Patent Document 1 is provided with a plurality of through holes in the positive electrode and the negative electrode in order to distribute lithium ions throughout the negative electrode. Therefore, there is a disadvantage that the effective area of the positive electrode and the negative electrode is reduced by the through hole, and further, there is a problem that a process of forming the through hole is necessary and the cost is increased.

  Moreover, although the electrochemical device described in Patent Document 1 distributes lithium ions through the through-holes, it actually takes a long time to perform pre-doping.

  An object of the present invention is to provide a method for producing an electrode for an electricity storage device and a method for producing an electricity storage device capable of reducing the time required for pre-doping without reducing the effective area of the electrode. .

  The present invention relates to a method for manufacturing an electrode for a power storage device and a method for manufacturing a power storage device, in which a strip-like structure in which a lithium foil is superimposed on both sides or one side of an electrode provided with an active material layer on both sides of a current collector is reeled. A winding step for winding the belt-shaped structure, holding the reel in a container containing a driving electrolyte solution, holding the container at a predetermined temperature, and holding the reel at the predetermined temperature. The method includes a drying step of drying the inside of the container after being held in a predetermined atmosphere, and a step of taking out the reel from the container and taking out the electrode from the reel.

  According to the present invention, a belt-like structure in which a lithium foil is superimposed on both sides or one side of an electrode provided with an active material layer on both sides of a current collector is wound around a reel and placed in a container containing a driving electrolyte. Hold and hold at a predetermined temperature. Then, since there is a potential difference between the electrode provided with the active material layer on both sides of the current collector and the lithium foil, lithium ions are transferred from the lithium foil to the electrode provided with the active material layer on both sides of the current collector. Doped. At this time, since the pre-doping is performed by directly contacting the lithium foil with the electrode provided with the active material layer on both sides of the current collector, lithium ions are applied to the entire electrode provided with the active material layer on both sides of the current collector. It is not necessary to provide through-holes for spreading in the electrode provided with active material layers on both sides of the current collector, and pre-doping is performed in a shorter time than when lithium ions are distributed through the through-holes. Can do. As a result, the time required for pre-doping can be shortened without reducing the effective area of the electrode.

It is a perspective view of an electrical storage device. It is a flowchart which shows the manufacturing method of an electrical storage device. It is a perspective view of a reel.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Configuration of electricity storage device)
As shown in FIG. 1 which is a perspective view, the electricity storage device 1 according to the present embodiment is formed by winding or laminating a negative electrode (an electrode having active material layers on both sides of a current collector) 2, a separator 4, and a positive electrode 3 ( The driving electrolyte solution (electrolyte solution) 5 is accommodated in the outer case 6 while being held by the separator 4. The negative electrode 2, the separator 4, and the positive electrode 3 are overlapped to form a strip. The band 7 is wound from one end in the length direction, whereby the element 7 is formed. This element 7 is accommodated in an outer case 6 containing the driving electrolyte 5.

  The negative electrode 2 has active material layers 2b formed on the front and back surfaces of a current collector 2a made of copper foil. In addition, the material of the negative electrode 2 is not limited to this.

  The negative electrode 2 is produced as follows. For example, a copper foil having a thickness of 15 μm is used as the current collector 2a, and an active material layer 2b having a thickness of 50 μm, for example, is formed on the front and back surfaces of the current collector 2a. In the active material layer 2b, the blending ratio of graphite, acetylene black, and binder is, for example, graphite: acetylene black: binder = 80: 10: 10. The binder has a blending ratio of polytetrafluoroethylene (hereinafter referred to as PTFE) and carboxymethyl cellulose (hereinafter referred to as CMC) of, for example, 5: 5.

The manufacturing method of the active material layer 2b is as follows. CMC, acetylene black, graphite, and PTFE are added to water in this order, and the mixture is stirred and kneaded to obtain a paste. This is coated on the current collector 2a to a thickness of 50 μm. After drying this at a temperature of 80 ° C., it is pressed at a linear pressure of 75 to 100 kgf / cm. As described above, the active material layer 2b having a thickness (single-sided thickness) of 30 μm and an electrode density of 1.2 to 1.5 g / cm ³ is manufactured, and then cut into a predetermined size to form the negative electrode 2.

  The positive electrode 3 is obtained by forming polarizable electrode layers 3b mainly composed of activated carbon on the front and back surfaces of a current collector 3a made of an aluminum foil. In addition, the material of the positive electrode 3 is not limited to this.

  The positive electrode 3 is produced as follows. As the current collector 3a, for example, an aluminum foil having a thickness of 30 μm is used, and this is electrolytically etched in a hydrochloric acid-based etching solution to roughen the surface. Subsequently, a phenol resin-based activated carbon powder having an average particle diameter of 5 μm and a water-soluble binder solution in which CMC having an average particle diameter of 0.05 μm, which is a conductivity imparting agent, is mixed at a weight ratio of 10: 1 and kneaded. Mix thoroughly with a machine. Thereafter, a dispersion solvent of methanol and water is added little by little to the kneaded product, and further kneaded to prepare a paste having a predetermined viscosity. This paste is applied to the front and back surfaces of the current collector 3a, and dried in air at 100 ° C. for 1 hour. As described above, after forming the polarizable electrode layer 3b, it is cut into a predetermined dimension to form the positive electrode 3.

  The separator 4 may be any material as long as it can insulate the positive electrode 3 and the negative electrode 2 from each other so that the non-aqueous electrolyte can permeate and ions can permeate, and a porous film, nonwoven fabric, or woven fabric structure can be used. As a material of the separator 4, natural cellulose, a cellulose derivative, polyolefin, or the like can be used.

  The outer case 6 is made of aluminum. Lead wires 8 are connected to the negative electrode 2 and the positive electrode 3, respectively. The lead wire 8 is drawn out of the outer case 6. A sealing body 9 is fitted into the opening 6 a of the outer case 6, and the opening 6 a of the outer case 6 is sealed with the sealing body 9 by drawing and curling the opening end of the outer case 6. Has been. A hole through which the lead wire 8 passes is provided in the sealing body 9 in advance.

  The driving electrolyte 5 is a liquid that plays a role of a solvent for moving lithium ions, and is a liquid that can stably hold lithium ions without being electrolyzed at a high voltage.

(Method for manufacturing electrode for power storage device and method for manufacturing power storage device)
The electricity storage device 1 having the above configuration is manufactured by the manufacturing method of the present embodiment. Hereinafter, a method for manufacturing an electrode for an electricity storage device and a method for manufacturing an electricity storage device will be described with reference to the flowchart of FIG.

First, a replacement process for holding the negative electrode 2 in the driving electrolyte is performed (step S101). Specifically, the strip-shaped negative electrode 2 in which the active material layer 2b is formed on the front and back surfaces of the current collector 2a is wound around a reel. The reel will be described later. The reel is accommodated in a container, and a driving electrolyte (for example, LBG-96533, 1 mol / L LiPF6 ethylene carbonate: diethyl carbonate (1: 1) V / V% (Kishida Chemical Co., Ltd.)) is injected into the container. Then, hold at room temperature for 12 hours or at 60 ° C. for 3 hours. The driving electrolyte is obtained by dissolving a lithium salt such as LiBF ₄ or LiPF _{6 in} a solvent such as ethylene carbonate, diethyl carbonate, or propylene carbonate.

  As shown in FIG. 3 which is a perspective view, the reel 21 for winding the negative electrode 2 has a pair of disk-shaped side plates 22 arranged to face each other. A spiral guide groove 23 is formed on the inner surface of the side plate 22. The negative electrode 2 is wound around the reel 21 while the end of the negative electrode 2 in the width direction is engaged with the guide groove 23. The length of the guide groove 23 is longer than the entire length of the negative electrode 2.

  The interval between the guide grooves 23 adjacent to each other in the radial direction (A direction) of the side plate 22 is set to a predetermined interval. Therefore, when the negative electrode 2 is wound around the reel 21, a predetermined interval is formed between the negative electrodes 2 adjacent to each other in the A direction. This predetermined interval is set to an interval at which the driving electrolyte sufficiently passes between the negative electrodes 2 adjacent in the A direction.

  An insertion port 24 is formed at the end of the guide groove 23 on the outer peripheral side of the side plate 22. The insertion port 24 is formed so as to expand larger than the width of the guide groove 23. This facilitates the insertion of the negative electrode 2 from the insertion port 24.

  The side plate 22 is formed with a through hole 25 that allows the outer surface of the side plate 22 to communicate with the guide groove 23. A plurality of through holes 25 are formed at a predetermined interval in the circumferential direction (B direction) of the side plate 22. Via this through-hole 25, the driving electrolyte can freely flow in and out between the outer surface side and the inner surface side of the side plate 22. Therefore, by allowing the driving electrolyte to flow from the outer surface side of the side plate 22 toward the inner surface side of the side plate 22, the entire negative electrode 2 can be immersed in the driving electrolyte without unevenness.

  By holding the negative electrode 2 in the driving electrolyte, the water adsorbed on the negative electrode 2 and the driving electrolyte are replaced. Thereby, the characteristic and quality of the negative electrode 2 can be stabilized. Further, by holding the negative electrode 2 in the driving electrolyte, it is possible to remove contaminants other than moisture and cutting waste of the current collector 2a generated when the negative electrode 2 is cut to a predetermined size.

  Returning to FIG. 2, after the replacement process is performed, an extraction process (step 102) for taking out the reel 21 from the container is performed. Specifically, the reel 21 on which the strip-shaped negative electrode 2 in which the adsorbed moisture and the driving electrolyte are replaced is taken out from the container. Then, the negative electrode 2 wound around the reel 21 is taken out from the reel 21.

  Next, a winding process is performed in which the belt-shaped structure in which the lithium foil is superimposed on the front and back surfaces of the negative electrode 2 is wound around the reel 21 (step S103). Specifically, a strip-shaped lithium foil (thickness 20 μm) is superposed on the front and back surfaces of the strip-shaped negative electrode 2 in which the adsorbed moisture and the driving electrolyte are replaced to form a strip-shaped structure. That is, the belt-like structure is formed from one surface to the other surface, a lithium foil having a thickness of 20 μm, an active material layer 2 b having a thickness of 30 μm, a current collector 2 a having a thickness of 15 μm, and an active material layer having a thickness of 30 μm. 2b and a 20 μm thick lithium foil are laminated in this order. The belt-like structure is again wound around the reel 21 shown in FIG. At this time, a predetermined interval is formed between the band-like structures adjacent in the A direction (see FIG. 3). In addition, you may change the thickness of lithium foil suitably. Alternatively, the lithium foil may be overlapped only on one side of the negative electrode 2 to form a belt-like structure.

  Next, a holding step is performed in which the reel 21 around which the belt-like structure is wound is held in a container containing a driving electrolyte, and the container is held at a predetermined temperature (step S104). Specifically, the reel 21 around which the belt-like structure is wound is accommodated in a container, and the driving electrolyte is injected into the container in which the reel 21 is accommodated. The container filled with the driving electrolyte is held at room temperature for 48 hours or at 60 ° C. for 12 hours. In addition, you may change suitably the time and temperature to hold | maintain.

  When the belt-like structure holds the driving electrolyte, there is a potential difference between the negative electrode 2 and the lithium foil, so that lithium ions are doped from the lithium foil into the negative electrode 2. At this time, since the negative electrode 2 and the lithium foil are directly contacted and pre-doping is performed, it is not necessary to provide the negative electrode 2 with a through hole for spreading lithium ions throughout the negative electrode 2 and lithium via the through hole. Pre-doping can be performed in a short time compared to spreading ions. As a result, the time required for pre-doping can be shortened without reducing the effective area of the electrode.

  In the holding step, a positive potential (for example, +4 V) may be applied to the lithium foil, and a negative potential (for example, 0 V) may be applied to the negative electrode 2. Lithium ions can be more preferably doped from the lithium foil into the negative electrode 2 due to the potential difference generated between the negative electrode 2 and the lithium foil. Thus, the time required for pre-doping can be further shortened by electrochemically pre-doping.

  In the holding step, the time required for pre-doping can be further shortened by holding the container at 30 ° C. or higher and 100 ° C. or lower.

  Here, in the conventional manufacturing method, a lithium foil is provided on the outer peripheral side of a strip in which a negative electrode, a separator, and a positive electrode are overlapped in this order, and this is immersed in an electrolytic solution. Pre-doping is performed by applying a negative potential. That is, the pre-doping is performed after the structure of the lithium ion capacitor is completed. On the other hand, in the manufacturing method of this embodiment, since the pre-doping is performed before the structure of the electricity storage device 1 is completed (the negative electrode 2, the separator 4, and the positive electrode 3 are overlapped), the number of production steps is reduced. Can do.

  Next, a drying process for drying the inside of the container after being maintained at a predetermined temperature in a predetermined atmosphere is performed (step S105). Specifically, the inside of the container is dried with a gas having a dew point temperature of −40 ° C. or lower or an inert gas. Thereby, since the driving electrolyte can be suitably removed from the negative electrode 2, the characteristics and quality of the negative electrode 2 can be stabilized.

  Thereafter, the reel 21 is taken out from the container, and a take-out process for taking out the negative electrode 2 from the reel 21 is performed (step S106). Specifically, the reel 21 around which the negative electrode 2 pre-doped with lithium is wound is taken out from the container. Then, the negative electrode 2 is taken out from the reel 21. As described above, the negative electrode 2 as the electrode for the electricity storage device is manufactured.

  Thereafter, lead wires 8 are connected to the negative electrode 2 and the positive electrode 3, respectively, and the negative electrode 2, the separator 4, and the positive electrode 3 are overlapped in this order to form a strip. The element 7 is formed by winding the strip from one end in the length direction. The element 7 is accommodated in an outer case 6 containing the driving electrolyte 5. The sealing body 9 is fitted into the opening 6 a of the exterior case 6 while the lead wire 8 is passed through the hole of the sealing body 9. The opening 6a of the outer case 6 is sealed with the sealing body 9 by drawing and curling the opening end of the outer case 6. Thus, the electricity storage device 1 is manufactured. In forming the element 7, the reel 21 may be used as a supply reel for the negative electrode 2.

(Evaluation of pre-doping time)
Next, the time required for the pre-doping of lithium ions into the negative electrode 2 (pre-doping time) in the method for manufacturing the electrode for the power storage device and the method for manufacturing the power storage device of the present embodiment and the conventional manufacturing method (conventional example) is as follows. evaluated. Here, in the conventional example, a large number of through-holes are provided in the negative electrode and the positive electrode, respectively, and a lithium foil is provided on the outer peripheral side of the belt-like material in which the negative electrode, the separator, and the positive electrode are overlapped in this order, and this is immersed in the electrolytic solution. In addition, pre-doping is performed by applying a positive potential to the lithium foil and a negative potential to the negative electrode, respectively, and lithium ions are distributed throughout the negative electrode through the through holes. Table 1 shows the pre-doping time when held at room temperature and the pre-doping time when held at 60 ° C.

  From Table 1, it can be seen that the pre-doping time in the present embodiment is reduced to half that of the conventional example.

(effect)
As described above, according to the method for manufacturing an electrode for an electricity storage device and the method for producing an electricity storage device according to the present embodiment, a belt-like structure in which lithium foil is superimposed on both sides or one side of the negative electrode 2 is wound on a reel 21. And kept in a container containing the driving electrolyte, and kept at a predetermined temperature. Then, since there is a potential difference between the negative electrode 2 and the lithium foil, the negative electrode 2 is doped with lithium ions from the lithium foil. At this time, since the negative electrode 2 and the lithium foil are directly contacted and pre-doping is performed, it is not necessary to provide the negative electrode 2 with a through hole for spreading lithium ions throughout the negative electrode 2 and lithium via the through hole. Pre-doping can be performed in a short time compared to spreading ions. As a result, the time required for pre-doping can be shortened without reducing the effective area of the electrode.

  In addition, when pre-doping is performed, a positive potential is applied to the lithium foil, and a negative potential is applied to the negative electrode 2, whereby a potential difference can be more appropriately generated between the negative electrode 2 and the lithium foil. By this potential difference, lithium ions can be preferably doped from the lithium foil to the negative electrode 2. Thus, the time required for pre-doping can be further shortened by electrochemically pre-doping.

  Moreover, when performing pre-doping, the time required for pre-doping can be further shortened by maintaining the container at 30 ° C. or higher and 100 ° C. or lower.

  Moreover, the electrolyte solution for driving can be suitably removed from the negative electrode 2 by drying the inside of the container with a gas having a dew point temperature of −40 ° C. or lower or an inert gas. Thereby, the characteristic and quality of the negative electrode 2 can be stabilized.

  The embodiment of the present invention has been described above, but only specific examples are illustrated, and the present invention is not particularly limited, and the specific configuration and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

  For example, in the present invention, the predetermined interval is secured between the negative electrodes 2 by the guide groove 23, but the same effect can be obtained even by a method other than the guide groove 23. That is, the band-shaped structure described in step S102 (a lithium foil having a thickness of 20 μm, an active material layer 2b having a thickness of 30 μm, a current collector 2a having a thickness of 15 μm, an active material layer 2b having a thickness of 30 μm, a lithium having a thickness of 20 μm). Since the driving electrolyte solution may circulate without being closely adhered in the reel 21, for example, a mesh-like polymer sheet having a thickness of about 100 μm with holes having an interval of 1 mm and an opening diameter of 1 mm is used as a spacer. Needless to say, the same effect can be obtained by winding together with the structure.

  Further, the driving electrolytes used in the substitution step, the holding step, and the electricity storage device of the present invention may have different compositions.

1 Power Storage Device 2 Negative Electrode (Electrode for Power Storage Device)
2a current collector 2b active material layer 3 positive electrode 3a current collector 3b polarizable electrode layer 4 separator 5 driving electrolyte (electrolyte)
6 Exterior Case 7 Element 8 Lead Wire 9 Sealing Body 21 Reel 22 Side Plate 23 Guide Groove 24 Insertion Port 25 Through-hole

Claims (6)

A winding step of winding a belt-like structure in which a lithium foil is superimposed on both sides or one side of an electrode provided with an active material layer on both sides of a current collector, on a reel;
Holding the reel around which the belt-like structure is wound in a container containing a driving electrolyte, and holding the container at a predetermined temperature; and
A drying step of drying the inside of the container after being held at the predetermined temperature in a predetermined atmosphere;
Taking out the reel from the container and taking out the electrode from the reel; and
The manufacturing method of the electrode for electrical storage devices characterized by having.   The holding step includes a storing step of storing the reel around which the belt-like structure is wound in the container, and an injection step of injecting the driving electrolyte into the container storing the reel. The manufacturing method of the electrode for electrical storage devices of Claim 1 characterized by these.   3. The method for manufacturing an electrode for an electricity storage device according to claim 1, wherein, in the holding step, a positive potential is applied to the lithium foil and a negative potential is applied to the electrode.   The method for manufacturing an electrode for an electricity storage device according to any one of claims 1 to 3, wherein in the holding step, the container is held at 30 ° C or higher and 100 ° C or lower.   5. The electrode for an electricity storage device according to claim 1, wherein in the drying step, the inside of the container is dried with a gas having a dew point temperature of −40 ° C. or less or an inert gas. Manufacturing method.   The electrode manufactured by the method for manufacturing an electrode for an electricity storage device according to any one of claims 1 to 5 is used as a negative electrode, and a positive electrode having a layer containing activated carbon and the negative electrode are wound through a separator. A method for manufacturing an electricity storage device, characterized by comprising:

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