JP6327090B2 - Method for manufacturing electrode for power storage device - Google Patents

Description

  The present invention relates to a method for manufacturing an electrode for a power storage device used in a power storage device such as a secondary battery or a capacitor.

  Power storage devices such as secondary batteries and capacitors are widely used as power sources because they can be recharged and can be used repeatedly. Conventionally, lithium ion secondary batteries, nickel-hydrogen secondary batteries, and the like are well known as power storage devices mounted on vehicles such as EVs (Electric Vehicles) and PHVs (Plug-in Hybrid Vehicles). In these secondary batteries, for example, a positive electrode and a negative electrode having an active material layer formed by applying a paste-like or slurry-like active material mixture containing an active material on the surface of a metal foil as a current collector, The electrode assembly is formed by, for example, stacking or winding with a porous and resin separator interposed therebetween, and the electrode assembly is housed in a case.

  Further, conventionally, with respect to the electrode assembly, efforts have been made to further improve the heat resistance of the insulating structure that suppresses a short circuit between the positive electrode and the negative electrode. As one of them, it has been proposed to arrange an insulating protective layer in addition to the resin separator between the positive electrode and the negative electrode. The protective layer is superior in heat resistance to the resin separator, and for example, there is one in which a ceramic layer made of fine ceramic particles is formed on the active material layer.

  An example of a method for manufacturing an electrode having such a ceramic layer will be described. First, an active material layer is formed continuously or intermittently in the longitudinal direction on a long strip-shaped current collector, and the surface of the current collector is formed. An active material layer is formed. Next, a slurry for protective coating in which ceramic particles are dispersed in a solvent is applied onto the active material layer while conveying the current collector on which the active material layer is formed in the longitudinal direction. Thereafter, the electrode material is passed through a drying device, and when the protective coating slurry is dried, a ceramic layer is formed on the active material layer. And the electrode which has a ceramic layer is manufactured by cut | disconnecting the electrical power collector with which the ceramic layer was formed in the surface of the active material layer in the shape of an electrode (for example, patent document 1).

JP 2006-48942 A

  By the way, Patent Document 1 describes that a drying device that dries hot slurry or infrared rays to dry the protective coat slurry may be used. However, hot wind or infrared rays are applied to the protective coat slurry from the outside. When heated, the solvent evaporates from the surface of the protective coating slurry applied to the active material layer, and a film having a high density of ceramic particles is formed on the surface. If such a film is formed, the leveling property is impaired, and if bubbles inside the protective coating slurry are repelled, a concave portion may be formed in a part of the ceramic layer. The concave portion is a portion where the active material layer is exposed or the thickness of the ceramic layer is extremely thin. If such a concave portion is formed in the ceramic layer, current is concentrated in the concave portion when the secondary battery is used, which is not preferable because the performance of the secondary battery is lowered or the life is shortened.

  Patent Document 1 also describes that a drying device that dries the slurry for protective coating using electromagnetic induction may be used, but in the case of induction heating using electromagnetic induction, The current collector generates heat, and the heat is transmitted from the inside to the protective coating slurry through the active material layer. However, since the active material layer has numerous voids that become ion passages when impregnated with the electrolytic solution, the active material layer has low thermal conductivity and heat is not easily transferred to the protective coating slurry. That is, the manufacturing method of drying the protective coating slurry by induction heating that generates heat from the current collector heats the protective coating slurry from the inside, so that it can suppress the formation of a film on the surface and form a smooth protective layer. There is a lot of heat conduction loss and the efficiency is not good.

  The present invention has been made in view of the above circumstances, and its purpose is to suppress loss of heat conduction and to smooth the surface of the active material layer more efficiently than the manufacturing method of drying the slurry for protective coating by induction heating. An object of the present invention is to provide a method for manufacturing an electrode for a power storage device capable of forming a protective layer.

  A method for manufacturing an electrode for a power storage device for solving the above problem is a method for manufacturing an electrode for a power storage device having a protective layer on the surface of an active material layer present on the surface of a metal current collector. In this production method, a protective coating slurry in which a protective coating material for forming the protective layer is dispersed in a solvent is applied to the surface of the active material layer, and the electrode precursor is coated with the protective coating slurry. A protective layer forming step of forming the protective layer by applying a high frequency electric field to heat the active material layer by dielectric heating and drying the slurry for protective coating applied to the surface of the active material layer; .

  In the dielectric heating, the metal current collector that is a conductor does not generate heat, but the active material contained in the active material layer generates heat. That is, the active material layer itself coated with the protective coating slurry generates heat. Therefore, according to the above manufacturing method, the heat conduction loss is suppressed more efficiently than the manufacturing method using induction heating in which the current is generated by the current collector and the protective coating slurry is dried by the heat transmitted through the active material layer. The slurry for protective coating can be heated well from the inside. Therefore, according to the manufacturing method described above, the protective coating slurry can be dried while suppressing the formation of a film on the surface, and a smooth protective layer can be efficiently formed on the surface of the active material layer.

Moreover, in said manufacturing method, it is preferable that the said protective coating material is a ceramic particle and forms a ceramic layer as said protective layer in the said protective layer formation process.
Ceramic particles that are dielectrics generate heat by dielectric heating. Therefore, according to the above manufacturing method, when a high frequency electric field is applied to the electrode precursor in the protective layer forming step, the ceramic particles themselves contained in the protective coating slurry generate heat, and the protective coating slurry dries quickly. It becomes like this.

  In the manufacturing method, in the protective layer forming step, the protective coat slurry is applied to both surfaces of the active material layer respectively present on both surfaces of the current collector, and the protective coat slurry is applied. A high frequency electric field is applied to the processed electrode precursor, both the active material layers existing on both sides of the current collector are heated by dielectric heating, and the protective layer is formed on both surfaces of the active material layer. May be.

  According to the above manufacturing method, both the active material layers existing on both sides of the current collector are heated by a single dielectric heating, and both of the protective coating slurries coated on the surfaces of the respective active material layers are dried. be able to.

  In the manufacturing method, in the protective layer formation step, the protective coating slurry is applied to the surface of the active material layer using a die coating method in which the slurry for protective coating discharged from a die head is applied to the surface of the active material layer. You may make it apply | coat a slurry.

  Further, in the manufacturing method, in the protective layer forming step, the surface of the active material layer is coated on the surface of the active material layer using a gravure coating method in which the slurry for protective coating scraped up by a gravure roll is applied to the surface of the active material layer. You may make it apply the slurry for protective coats.

  As a coating method for applying the protective coating slurry to the surface of the active material layer, in addition to the die coating method and the gravure coating method, a spray coating method in which the coating liquid is sprayed on the substrate may be considered. Since the film thickness is controlled by recoating the coating liquid on the base material, it is difficult to adjust the film thickness. When the film thickness is increased, the leveling property is impaired.

  On the other hand, if the die coating method is to coat the substrate by extruding the coating liquid from the die head, the leveling property is less likely to be impaired even if the film thickness is increased compared to the spray coating method. Therefore, according to said manufacturing method, it becomes easy to form a smooth protective layer compared with the spray coat method.

  In addition, the gravure coating method in which the substrate is coated with the coating liquid scraped up by the gravure roll can smoothly coat the low-viscosity coating liquid, and the film thickness can be easily adjusted. Therefore, according to said manufacturing method, it becomes easy to form a smooth protective layer compared with the spray coat method.

In addition, the above manufacturing method may include a pressing step in which the active material layer having the protective layer formed on the surface through the protective layer forming step is compressed together with the protective layer.
According to the above manufacturing method, the density of the active material layer is adjusted by compressing the active material layer, and the protective layer formed on the surface of the active material layer is brought into close contact with the active material layer to be difficult to peel off. Can do. That is, productivity can be improved by combining the pressing process for adjusting the density of the active material layer and the pressing process for closely attaching the protective layer to the active material layer into one pressing process.

  According to the present invention, a smooth protective layer can be efficiently formed on the surface of the active material layer.

The perspective view of the electrode manufactured by the manufacturing method of an embodiment. The flowchart which shows the procedure of each process in the manufacturing method of the embodiment. The schematic diagram of the production equipment used at a protective layer formation process. Sectional drawing which cut | disconnected the electrode precursor in the width direction. The schematic diagram which shows the coating method by the gravure coat method. The schematic diagram which shows the other coating method.

Hereinafter, an embodiment embodying a method for manufacturing an electrode for a power storage device will be described with reference to FIGS.
Although not shown, the secondary battery as a power storage device using the electrode manufactured through the manufacturing method of this embodiment is a rectangular battery having a rectangular external appearance, and is a lithium ion battery. This secondary battery includes an electrode assembly in a case. The electrode assembly includes a plurality of positive electrodes and a plurality of negative electrodes, and the positive electrode electrode and the negative electrode are insulated from each other by a porous and resin separator. It is configured to be alternately stacked in a state.

  As shown in FIG. 1, an electrode 10 as a power storage device electrode used in the secondary battery includes a rectangular metal foil 11 as a current collector and a rectangular shape provided on both surfaces of the metal foil 11. An active material layer 12 and a ceramic layer 13 as a protective layer indicated by dot hatching covering the entire surface of the active material layer 12 are provided. The ceramic layer 13 has an insulating function to suppress a short circuit between the stacked electrodes 10 and has heat resistance. The electrode 10 has an uncoated portion 12 a along which the active material layer 12 is not provided and the metal foil 11 is exposed. And in the electrode 10, the current collection tab 14 is provided in the state which protrudes in a part of uncoated part 12a. The active material layer 12 is configured such that the active material particles are fixed to each other by a resin binder, and a large number of voids serving as electrolyte and ion passages are provided between the active materials. The ceramic layer 13 is composed of ceramic particles as a protective coating material having electrical insulation and a resin binder. The ceramic particles in this embodiment are alumina particles, and the ceramic layer 13 includes a large number of voids as in the active material layer 12. The ceramic layer 13 is preferably thin and flat.

Next, a method for manufacturing the electrode 10 will be described.
As shown in FIG. 2, the manufacturing method of this embodiment includes a kneading step S1, an active material layer forming step S2, a protective layer forming step S3, a pressing step S4, a cutting step S5, and a reduced pressure drying step S6. And a punching step S7.

  In the kneading step S1, an active material mixture is produced by kneading an active material, a binder, a solvent and, if necessary, a conductive additive and a thickener. When the electrode is a positive electrode, a positive electrode active material is used as the active material, and when the electrode is a negative electrode, the negative electrode active material is used as the active material.

  Active material layer formation process S2 is a process of apply | coating an active material mixture to the strip | belt-shaped metal foil as a metal electrical power collector, and includes a surface coating process and a back surface coating process. In the surface coating process, the strip-shaped metal foil is fed out from the supply reel, the active material mixture is applied to one surface (surface) of the strip-shaped metal foil with a coating device, and the active material mixture is dried through a drying device. After being wound, it is wound on a winding reel. In the back surface coating process, after the active material mixture is applied and dried on one surface in the surface coating process, the active material mixture is applied to the other surface (back surface) of the strip-shaped metal foil wound on the winding reel. After the agent is applied and dried, it is wound on a winding reel. Inside the drying device (not shown), hot air of 80 to 100 degrees is supplied, the solvent evaporates from the active material mixture on the metal foil passing through the inside, and the active material particles are mutually bonded by the action of the binder. To form an active material layer on the metal foil. In the active material layer after passing through the drying device, there are relatively large voids between the active material particles.

  In the protective layer forming step S3, the slurry for protective coating is applied to the surface of the active material layer formed on the surface of the strip-shaped metal foil, and after the coating, the slurry for protective coating is dried through a drying device. A ceramic layer is formed on the surface of the material layer. The electrode precursor on which the ceramic layer is formed is wound up on a winding reel.

  In the pressing step S4, the belt-shaped electrode precursor in which the ceramic layer is formed on the surface of the active material layer in the protective layer forming step S3 is compressed by roll pressing. At this time, the gaps between the active material particles in the active material layer are narrowed, but a sufficient width is ensured to be impregnated with the electrolyte and serve as an ion passage.

In the cutting step S5, the strip-shaped electrode precursor after the pressing step S4 is cut. In this embodiment, the strip-shaped electrode precursor is cut in the longitudinal direction so as to have a width corresponding to one electrode.
In the reduced pressure drying step S6, the strip-shaped electrode precursor is placed in a drying furnace in a wound state. By storing in a drying furnace under reduced pressure and high temperature for several hours to several tens of hours, a slight amount of solvent (water Or the non-aqueous solvent) is evaporated.

In the punching step S7, individual electrodes are punched from the strip-shaped electrode precursor. In this embodiment, an electrode having a tab for a laminated electrode assembly is punched out.
Among the above seven steps, other steps except the protective layer forming step S3, that is, the kneading step S1, the active material layer forming step S2, the pressing step S4, the cutting step S5, the vacuum drying step S6 and the punching step S7 are conventional electrodes. Since it is basically the same as each step in the manufacturing process, the protective layer forming step S3 will be mainly described below.

  As shown in FIG. 3, the production facility 20 used in the protective layer forming step S3 includes a coating device 23 for applying the protective coating slurry 13a to the surface of the active material layer 12 present on both surfaces of the metal foil 11, A drying device 30 for drying the protective coat slurry 13a. The protective coating slurry 13a is composed of ceramic particles that are protective coating materials, a binder, and a solvent.

  The production facility 20 has a supply roll 21, and a metal foil 11 having an active material layer 12 on both sides is wound around the supply roll 21. The supply roll 21 is rotatably supported by a support device (not shown). Moreover, the production facility 20 has a winding roll 22, and the winding roll 22 is rotatably supported by a support device (not shown). Furthermore, the production facility 20 has a plurality of transport rolls 29 that support the metal foil 11. Then, the metal foil 11 supplied from the supply roll 21 is wound around the rotating take-up roll 22, so that the metal foil 11 is transported at a constant speed while being supported by the transport roll 29.

  The coating device 23 includes a first die head 23 b, and a discharge port (not shown) of the first die head 23 b faces the active material layer 12 existing on the lower surface of the metal foil 11 below the metal foil 11. Has been placed. Further, the coating apparatus 23 includes a second die head 23 a, and an outlet (not shown) of the second die head 23 a is above the metal foil 11 and the active material layer 12 present on the upper surface of the metal foil 11. Are arranged opposite to each other.

  In the coating process, the protective coating slurry 13a is continuously applied from the discharge port of the first die head 23b to the surface of the active material layer 12 existing on the lower surface of the metal foil 11, and the discharge of the second die head 23a is performed. The protective coating slurry 13a is continuously applied to the surface of the active material layer 12 existing on the upper surface of the metal foil 11 from the outlet.

  As a result, as shown in FIG. 4, the metal foil 11 as a current collector, the active material layer 12 formed on both surfaces of the metal foil 11, and the slurry for protective coating applied to the surface of the active material layer 12 The electrode precursor 15 provided with 13a is formed. The active material layer 12 is formed on the metal foil 11 so that uncoated portions 12a exist on both sides of the electrode precursor 15 in the width direction.

  As shown in FIG. 3, the drying device 30 includes a first electrode 31, a second electrode 32, and a high-frequency power source 33. The first electrode 31 and the second electrode are disposed to face each other with the electrode precursor 15 coated with the protective coating slurry 13a through the coating device 23. A high frequency power source 33 is connected to the first electrode 31 and the second electrode 32.

  The drying device 30 dielectrically heats the electrode precursor 15 by applying a high-frequency electric field to the electrode precursor 15 positioned between the first electrode 31 and the second electrode 32 by the high-frequency power source 33. As a result, the solvent contained in the protective coating slurry 13a evaporates, and the ceramic particles or the ceramic particles and the active material layer 12 are bonded by the binder. That is, the protective coating slurry 13 a is dried, the ceramic particles are fixed on the active material layer 12, and the ceramic layer 13 as a protective layer is formed on the surface of the active material layer 12. The strip-shaped electrode precursor 15 on which the ceramic layer 13 is formed through the drying device 30 is wound around the winding roll 22.

  The active material layer 12 having the ceramic layer 13 as a protective layer formed on the surface is compressed so as to have a predetermined density together with the ceramic layer 13 in the pressing step S4 as described above.

Next, the operation of the manufacturing method of this embodiment will be described.
In the protective layer forming step S3, the protective coating slurry 13a is dried by dielectric heating. However, in the dielectric heating, the metal foil 11 as a conductor does not generate heat, but the active material contained in the active material layer generates heat. That is, the active material layer 12 coated with the protective coating slurry 13a generates heat.

  Moreover, the ceramic particles that are dielectrics generate heat by dielectric heating. Therefore, according to this manufacturing method, when a high frequency electric field is applied to the electrode precursor 15 in the protective layer forming step S3, the ceramic particles themselves contained in the protective coating slurry 13a also generate heat.

  Therefore, the protective coat slurry 13a is easily heated from the inside, and a film is less likely to be formed on the surface of the protective coat slurry 13a as compared with the case where the protective coat slurry 13a is heated from outside by applying hot air or infrared rays.

According to the manufacturing method described above, the following effects can be obtained.
(1) According to this manufacturing method, induction heating is used to heat the metal foil 11 as a current collector and dry the protective coating slurry 13a by heat transmitted through the active material layer 12 having voids therein. The loss of heat conduction can be suppressed as compared with the manufacturing method, and the protective coating slurry 13a can be efficiently heated from the inside. Therefore, the protective coating slurry 13 a can be dried while suppressing the formation of a film on the surface, and the smooth ceramic layer 13 can be efficiently formed on the surface of the active material layer 12.

  (2) When a high frequency electric field is applied to the electrode precursor 15 in the protective layer forming step S3, the ceramic particles themselves contained in the protective coating slurry 13a also generate heat, so that the protective coating slurry 13a is quickly dried.

  (3) According to this manufacturing method, the protective coating slurry 13a was applied to both surfaces of the active material layer 12 present on both surfaces of the metal foil 11, and the protective coating slurry 13a was applied to both surfaces. The electrode precursor 15 is dielectrically heated by the drying device 30. Therefore, both the active material layers 12 existing on both surfaces of the metal foil 11 are heated by one dielectric heating, and both the protective coating slurry 13a applied to the surface of each active material layer 12 can be dried. .

  (4) As a coating method for applying the protective coating slurry 13a to the surface of the active material layer 12, a spray coating method in which a coating liquid is sprayed on the substrate may be considered. Since the film thickness is controlled by recoating the coating liquid, it is difficult to adjust the film thickness. When the film thickness is increased, the leveling property is impaired. On the other hand, as in the manufacturing method of this embodiment, if the die coating method is to coat the substrate by extruding the coating liquid from the die head, leveling properties can be achieved even if the film thickness is increased compared to the spray coating method. Is hard to be damaged. Therefore, according to the manufacturing method of this embodiment, it is easy to form the smooth ceramic layer 13 as compared with the spray coating method.

  (5) In this manufacturing method, the pressing step S4 is performed after the active material layer forming step S2 and the protective layer forming step S3. Therefore, by compressing the active material layer 12, the density of the active material layer 12 is adjusted, and the ceramic layer 13 formed on the surface of the active material layer 12 is brought into close contact with the active material layer 12 to be difficult to peel off. it can. That is, in this manufacturing method, the pressing process for adjusting the density of the active material layer 12 and the pressing process for closely attaching the ceramic layer 13 as a protective layer to the active material layer 12 are combined into one pressing process. Therefore, productivity becomes high compared with the case where these press processes are performed separately.

In addition, you may change the said embodiment as follows.
The ceramic layer 13 may be sequentially formed on each side of the metal foil 11 having the active material layer 12 formed on both sides.

(Circle) the coating method which apply | coats the slurry 13a for protective coats on the surface of the active material layer 12 in protective layer formation process S3 can be changed suitably.
The protective coating slurry 13a may be applied to the surface of the active material layer 12 using a gravure coating method in which the coating liquid scraped up by the gravure roll is applied to the surface of the active substrate. For example, as shown in FIG. 5, among the active material layers 12 existing on both surfaces of the metal foil 11 by scraping the protective coat slurry 13 a accommodated in the slurry container 41 with the gravure roll 40, The protective coating slurry 13a is applied to the surface of the active material layer 12 existing on the lower surface. The tension of the metal foil 11 is adjusted by the pair of guide rolls 42 and 43 and is pressed against the gravure roll 40. In the gravure coating method, a low-viscosity coating liquid can be coated smoothly and the film thickness can be easily adjusted. Therefore, even when a production method using a gravure coating method is employed, a smooth protective layer can be easily formed as compared with a spray coating method.

  In addition, a comma coating method in which a coating liquid adhered to a coating roll using a comma roll is transferred to a substrate can also be used. For example, in this case, as shown in FIG. 6, a slurry supply unit 51 for supplying the protective coating slurry 13 a and a comma roll 52 are disposed on the upper side of the coating roll 50, and a back roll is provided near the side of the coating roll 50. 53 is disposed. In addition, the coating roll 50 and the back roll 53 rotate in the same rotation direction. According to such a configuration, the protective coating slurry 13 a adheres to the surface of the coating roll 50 with a predetermined thickness by the rotation of the coating roll 50 and is transferred to a position facing the back roll 53. Moreover, after the metal foil 11 in which the active material layer 12 exists on both surfaces passes through the position facing the back roll 53 from the lower side to the upper side while being pressed to the coating roll 50 side by the rotation of the back roll 53, The moving direction is changed, the guide roll is guided to a guide roll (not shown), and the roll is wound around a roll roll (not shown). As a result, while the metal foil 11 passes through the facing position between the coating roll 50 and the back roll 53, the protective coating slurry 13a adhering to the coating roll 50 is transferred to the active surface existing on the upper surface of the metal foil 11. A protective coating slurry 13 a is applied to the surface of the material layer 12.

In addition, a spray coating method can also be employ | adopted as a coating method.
The ceramic particles as the protective coating material are not limited to alumina, and may be other metal oxides or metal nitrides, for example.

  ○ The protective layer is not limited to a ceramic layer. That is, the protective coating material is not limited to ceramic particles, and may be any material that satisfies electrical insulation and necessary heat resistance, and may be particles made of a thermosetting resin, for example.

○ A protective layer may be formed on each side.
O You may make it implement separately the press process which adjusts the density of the active material layer 12, and the press process which adheres a protective layer to the active material layer 12.

  In the embodiment, the protective layer is formed on the active material layer 12 provided continuously in the longitudinal direction of the metal foil 11, but the protective layer is formed on the active material layer 12 provided intermittently in the longitudinal direction of the metal foil 11. May be.

The current collector is not limited to the metal foil 11 as long as the active material layer 12 can be formed. For example, a woven or net-like substrate sheet may be used.
The electrode 10 may have an active material layer 12 and a protective layer only on one side of the metal foil 11.

○ The electrode 10 may be either a negative electrode or a positive electrode.
(Circle) You may apply to the manufacturing method of the electrode for not only the manufacturing method of the electrode for lamination type electrode assemblies but a winding type electrode assembly.

  The secondary battery in which the electrode assembly is used is not limited to a lithium ion secondary battery, but may be another secondary battery such as a nickel hydride secondary battery or a nickel cadmium secondary battery.

  DESCRIPTION OF SYMBOLS 11 ... Metal foil as a collector, 12 ... Active material layer, 13 ... Ceramic layer as a protective layer, 13a ... Slurry for protective coating, 15 ... Electrode precursor, S3 ... Protective layer formation process, S4 ... Press process, 23a ... second die head, 23b ... first die head, 40 ... gravure roll.

Claims (6)

A method for producing an electrode for a power storage device having a protective layer on the surface of an active material layer present on the surface of a metal current collector,
The protective coating material for forming the protective layer is coated on the surface of the active material layer with a protective coating slurry dispersed in a solvent, and a high frequency electric field is applied to the electrode precursor coated with the protective coating slurry. A protective layer forming step of heating the active material layer by dielectric heating and forming the protective layer by drying the protective coating slurry applied to the surface of the active material layer. Production method.   The method for manufacturing an electrode for a power storage device according to claim 1, wherein the protective coating material is ceramic particles, and a ceramic layer is formed as the protective layer in the protective layer forming step.   In the protective layer forming step, the protective coating slurry is applied to both surfaces of the active material layer respectively present on both surfaces of the current collector, and the electrode precursor coated with the protective coating slurry has a high frequency. 3. The protective layer according to claim 1, wherein an electric field is applied and both the active material layers existing on both surfaces of the current collector are heated by dielectric heating to form the protective layer on both surfaces of the active material layer. A method for manufacturing an electrode for a power storage device.   2. The protective coating slurry is applied to the surface of the active material layer using a die coating method in which the protective coating slurry discharged from a die head is applied to the surface of the active material layer in the protective layer forming step. The manufacturing method of the electrode for electrical storage apparatuses as described in any one of Claims 3-5.   In the protective layer forming step, the protective coat slurry is applied to the surface of the active material layer by using a gravure coating method in which the slurry for protective coating that has been scraped up by a gravure roll is applied to the surface of the active material layer. The manufacturing method of the electrode for electrical storage apparatuses as described in any one of Claims 1-2.   The power storage device according to any one of claims 1 to 5, further comprising a pressing step of compressing the active material layer having the protective layer formed on the surface through the protective layer forming step together with the protective layer. Electrode manufacturing method.