JP7054164B2 - Capacitive energy storage device and method of making the device - Google Patents

Description

[0001] The present invention relates to a capacitive energy storage device, a method for making a capacitive energy storage device, and the use of a porous film for making a stacked capacitive energy storage device. Specifically, a capacitive energy storage device is one of the capacitive electrodes in which at least one porous film infiltrated with an electrolyte is formed on the surface of the film and ionically communicates with the electrolyte in the internal pores of the film. Prepared with or more pairs.

[0002] The growing influence of miniaturized electronic devices in today's lives is driving more and more research into the development of miniaturized energy storage systems. Power supply systems often occupy more than 50% of the volume or weight of the device, typically a major shackle for miniaturization. Batteries have traditionally benefited from relatively high energy densities, but the challenges of scaling while maintaining the battery's low power, limited cycle life and electrochemical performance are high performance as a battery replacement. It has aroused interest in supercapacitors. These devices provide balanced energy and power density, fast charge / discharge capabilities (many orders of magnitude higher than Faraday elements), long life, maintenance-free operation, and low environmental impact. Therefore, supercapacitors, whether alone or integrated with battery systems, are attractive energy sources for many applications.

[0003] Traditional supercapacitors are typically made by coating a metal current collector foil with a thickness of 100 microns with a porous carbon electrode material. Two such electrodes are then assembled face-to-face with an acceptable porous separator in between to provide electrical insulation as depicted in FIG. The electrolyte saturates the separator and electrodes, and the device is electrically connected to an external circuit via a current collector. Porous electrodes store charges in the form of ions predominantly located in the electric double layer of high surface area carbon electrode material. Therefore, such a device is known as an electric double layer (EDL) supercapacitor.

[0004] In such EDL supercapacitors, the electrode separation distance is dominated by the thickness of the separator, so the electrodes are separated by at least 50-100 microns. The relatively long distance traversed by the ions during charging and discharging limits the power density of the device. Also, the large surface area of the electrodes, that is, the surface area that extends over the cross-sectional area of the supercapacitor device and is therefore typically in the range of mm ² to cm ² , allows efficient electron transport between these electrodes and external circuits. Forces the use of metal current collectors for. Thus, the current collector, separator, and inter-component junctions contribute to device dead volume, weight increase, and flexibility reduction.

[0005] In an attempt to solve these inconveniences, in-plane electrode geometry has been developed to provide microsupercapacitors with improved energy densities compared to traditional supercapacitors. In these devices, the insulating substrate is typically patterned with a conductive metal pad of the required electrode geometry, on which the electrode material is deposited by electrochemical deposition or other techniques. Will be done. An electrolyte layer deposited on the substrate provides ion communication between the electrodes across the surface, while the metal pads act as current collectors. While such techniques avoid some of the limitations of traditional electrode-separator-electrode type configurations, the reachable electrode resolution is generally insufficient to produce electrode separation distances in the 1-50 micron range. Therefore, a complicated multi-step process is required for production.

[0006] In recent years, direct "writing" techniques have made it possible to fabricate truly micron-scale electrodes with in-plane configurations. In this technique, an insulating graphene oxide layer is coated on a substrate and a focused beam is used to selectively reduce graphene oxide to a conductive high surface area graphene so that the electrodes are "written" to the layer. There is. The resulting graphene electrodes are separated by an intermediate graphene oxide capable of retaining the electrolyte pool required for ion communication between the electrodes. Thus, both lasers and focused ion beams provide high resolution comb electrodes, as described in El Kady et al, Nature Communications 2013, 4, 1475 and Lobo et al, Advanced Energy Materials 2015, 19, 1500665. Has been used to transfer in.

[0007] In the latter study, electrodes with a distance between electrodes as small as 1 micron were produced, resulting in capacitance per area greater than 100 mFcm ^-2 and ultrafast cycling response. This superior performance is due to the micron-scale resolution of the electrodes, specifically from the linear diffusion in dynamic control that occurs below the critical electrode dimensions that are believed to be below 50 microns. Due to the conversion of the ion transport mechanism to radial diffusion.

[0008] This study has demonstrated a microsupercapacitor that has a higher energy density than thin-film lithium-ion batteries, yet has extremely good power density and cycleability, but the direct write method is a beam reduction technique. Due to its dependence on, there are challenges in scaling up to industrial production. Moreover, the direct writing technique is expensive because it is a slow process and the porous GO layer is both an electrode precursor (which is subsequently reduced to form the electrode) and an insulating spacer between the reduced electrodes. This means that the electrode material is used relatively inefficiently. Also, as a result of beam reduction techniques, substrates are limited to non-porous materials such as silicon wafers. As a result, microsupercapacitors become undesirably rigid, limiting their applicability to flexible electronic devices. Moreover, the electrolyte pool exists only above the flat surface of the substrate surface, that is, typically as a layer of gel electrolyte on the substrate, which adds to the thickness of the device and thus the volumetric power density. And the energy density becomes smaller.

[0009] Therefore, there continues to be a need for improved capacitive energy storage devices and methods of making such devices with excellent energy density and / or power density that address one or more of the above drawbacks. Exists.

[0010] References to patent documents or other materials in the present specification given as prior art either endorse that the documents or materials were known or the information contained therein is the scope of the claims. It should not be taken as an endorsement that it was part of the well-known general knowledge as of the priority date of the claim.

El Kady et al., Nature Communications, 2013, 4, 1475 (El Kady et al, Nature Communications 2013, 4, 1475) Robo et al., "Advanced Energy Materials", 2015, 19, 1500265 (Lobo et al, Advanced Energy Materials 2015, 19, 1500665)

[0011] The inventors have now made a capacitive energy storage device and the device in which a capacitive electrode material applied to a porous film forms a plurality of pairs of separated electrodes on the surface of the film. Developed the method. The film is generally a film that has properties similar to a separator in a conventional supercapacitor and is due to the electrolyte so that when in use it provides ion communication through the film's internal pores between the isolation electrodes. It is porous enough to serve as a reservoir. Ionic Conductive Paths Through the Inside of the Film-Optionally augmented by additional Ionic Conductive Pathways Across the Surface of the Film and / or in Multilayer Stacks by additional Ionic Conductive Pathways Through the Porous Film Overlaid Overlaid. It is believed that the accessibility of the electrolyte to the microelectrode from multiple directions reduces the resistance associated with electrolyte diffusion, thus enhancing the electrochemical performance of the device. Additional or alternative, the utilization of porous substrates as electrolyte pools makes it possible to minimize the thickness of the electrolyte stack on the substrate, or to eliminate such layers altogether. Make it possible. Thus, the volume of the device is reduced while maintaining satisfactory ionic conductivity between the electrodes. In addition, the pores in the film are thought to facilitate the production of high-resolution electrodes, which will be explained in more detail later.

[0012] Accordingly, the invention is, according to a first aspect, a capacitive energy storage device: at least one porous film infiltrated with an electrolyte; and on a first surface of the porous film. One or more pairs of isolated electrodes arranged, wherein each electrode has a pair of separated electrodes, each of which has a capacitive electrode material that communicates ionically with the underlying porous film, and the electrolyte is porous. Provided is a capacitive energy storage device, which provides ion communication between the separation electrodes through the internal pores of the film.

[0013] Porous films generally have two surfaces on opposite sides of the film. As used herein, the "first surface" and "back surface" of the porous film refer to these opposite surfaces and are terms used to differentiate the surfaces from each other and are themselves. Does not imply any difference between the surfaces.

[0014] The porous film has internal pores that communicate with at least the first surface, typically both the first surface and the back surface. The internal pores of a porous material are internal voids or pores dispersed through a solid substrate. The pores of the porous film are interconnected so that the porous film is permeable to the liquid and can therefore be infiltrated with the electrolyte. As will be appreciated by those skilled in the art, the internal pores of a porous film are such as pore size, porosity (also known as void ratio, i.e., the percentage occupied by pores in the total volume), and surface area. Can be characterized by various parameters.

[0015] In some embodiments, at least 80%, preferably at least 90%, or substantially all of the total electrolyte is infiltrated into the internal pores of the porous film within the capacitive energy storage device. Therefore, the space occupied by the discrete layers of electrolyte in the device is minimized.

[0016] In use here, the "pair of separation electrodes arranged on the first surface of the porous film" is at least partially formed above the continuous surface of the underlying porous film. Thus, it refers to a pair of electrically isolated electrodes having a three-dimensional physical structure protruding from the surface, and the electrodes are separated from each other by a portion of the surface of a porous film in between. The electrode comprises a capacitive electrode material that communicates with the underlying porous film in ions. The capacitive electrode material provides ion communication with the underlying porous film when electrolyte ions can move through the porous film surface between the electrode and the internal pores of the underlying porous film portion. Please understand that there is. The capacitive electrode material may be in direct contact with and / or adhered to or bonded to the surface of the first porous film in a preferred embodiment, but the requirement for "ion communication" is non-existent. It should be understood that it does not exclude other engagement modes in which adhesive contact engagement, partial penetration of the capacitive electrode material into the film internal pores or ion communication is adequately provided.

[0017] In some embodiments, the pair of isolated electrodes has an inter-electrode separation distance of less than about 50 microns, preferably less than 30 microns. When used here, the separation distance between the electrodes is the minimum distance across the portion of the first surface of the porous film located between the separation electrodes, and is the minimum distance that ensures that the electrodes are electrically isolated from each other. Is. The narrow inter-electrode separation distance reduces the diffusion length scale for ions, thereby providing improved time and frequency response and / or improved power density. In some embodiments, the pair of separating electrodes has a distance between the electrodes that is smaller than the thickness of the porous film. Such separation distances are essentially not available in conventional supercapacitor designs where the electrodes are located on either side of the porous separator film.

[0018] In some embodiments, each pair of separated electrodes, including both the electrode itself and the inter-electrode separation area, has a surface area of less than about 1 mm ² on the porous film, eg, less than 0.5 mm ² . , Covering. In use here, the inter-electrode separation area is an area on the first surface of the porous film located between the separation electrodes, and is an area that reliably electrically isolates the electrodes from each other. Conveniently, for such small electrodes, charge transport dynamics are believed to be controlled by a radial diffusion mechanism, resulting in improved capacitance and energy density. In addition, such electrodes have sufficient electrical conductivity and do not require an additional current collector, i.e. a foil or other metal layer covering the in-plane area of the electrode. Therefore, in some embodiments, the electrodes of the capacitive energy storage device are electrically connected to adjacent electrodes and / or to an external circuit without a metal current collector.

[0019] In some embodiments, a pair of isolated electrodes is a comb-shaped electrode, each electrode having 2 to 6 fingers, preferably 3 to 5 fingers, such as 4 fingers. It is equipped with. Each finger can have a width of less than about 50 microns and a length of less than about 250 microns.

[0020] In some embodiments, the electrodes have an out-of-plane thickness between about 25 nm and about 1 micron. In use here, the out-of-plane thickness means the distance at which the electrode protrudes from the first surface of the porous film.

[0021] In some embodiments, a plurality of pairs of isolation electrodes are electrically connected and arranged in series and / or in parallel on the first surface of the porous film. Depending on the energy and power requirements for any particular application, it can be broadly included, including multiple parallel electrode pairs, multiple series electrode pairs, blocks of parallel connected electrode pairs connected in series, and so on. Various electrode pair configurations can be provided on the porous film. As will be appreciated by those skilled in the art, the total capacitance of parallel electrode pairs increases as the sum of the capacitances of the individual electrode pairs. In contrast, the series combination of electrode pairs reduces the total capacitance, but the applied voltage increases linearly with the number of electrode pairs. Since the energy density of the capacitor is directly proportional to the square of the applied voltage, the energy density of the device increases linearly with the increase in the number of pairs of electrodes connected in series.

[0022] Also, efficient utilization of the surface area of the porous substrate maximizes the number of isolated electrode pairs within a given area of the first surface of the substrate, thereby minimizing the unused space between the electrode pairs. It will be understood that it is provided by doing. In some embodiments, more than 10 electrode pairs per cm ² surface, preferably more than 50 electrode pairs, such as more than 80, are placed on the first surface of the porous film. .. In this method, the dead volume in the device is small, and the energy density and power density per unit device volume are maximized.

[0023] In some embodiments, the plurality of pairs of isolated electrodes are electrically connected by a conductive linkage on the first surface of the porous film, and the conductive linkage also comprises a capacitive electrode material. In these and other embodiments, a pair of isolation electrodes or a plurality of pairs of electrically connected isolation electrodes are provided with electrical contacts for electrical connection to an external circuit, and the electrical contacts are also capacitive. It is equipped with a sex electrode material. Such an embodiment conveniently provides an extended network of electrically connected electrode pairs, typically in a single printing process, in a single configuration for connecting to an external circuit. By applying a conductive material (or its reducible precursor), it can be made on a porous film, which simplifies the making of devices. It is desirable that the length of the conductive linkage between the electrode pairs be minimized to minimize the voltage drop across the linkage so that the power performance of the device is not compromised. In this regard, in other embodiments, the electrical contacts for connection to a pair of conductive linkages or external circuits of electrodes on the same porous film are provided with other conductive materials, including metal. It should be understood that it can also be done. This would be suitable, for example, to reduce the internal resistance of the energy storage device.

[0024] In some embodiments, a plurality of porous films are stacked and one or more pairs of isolation electrodes disposed on the first surface of the first porous film. They are stacked so as to be in contact with, for example, abutting and engaging with the back surface of the second porous film stacked above the first porous film. It is preferable that the contact provides ion communication between the electrode and the back surface. When a plurality of porous films are stacked in this manner, the separation electrode of the first film is sandwiched between the two porous films each infiltrated with an electrolyte, and the two porous films and the two porous films are sandwiched between the two porous films. Ion communication. Thus, the electrolyte can provide an ion communication path between the isolation electrodes through the internal pores of both the first and second porous films. The electrodes are effectively surrounded by pools of electrolytes contained in the first and second porous films on all sides, thus minimizing the dead volume of capacitive energy storage devices while further providing electrochemical performance. It will be strengthened. Moreover, especially when the porous film is a flexible film, the adjacent porous films fit closely around the electrodes sandwiched between them, so that the films can be stacked virtually without gaps between the films. Can be weighted. Thus, at least 90% of the total electrolyte in the device, preferably substantially all, can be infiltrated into the internal pores of the stacked porous film. The volumetric energy density and power density of the device are thus increased.

[0025] Two or more porous films may be stacked. As is obvious to those skilled in the art, when more than two porous films are stacked, each porous film having both upper and lower adjacent films in the stack is placed on the first surface of it. It may be defined as a first porous film in that one or more pairs of separated electrodes are in contact with the back surface of the adjacent film above it. It may also be defined as a second porous film in that the surface is in contact with one or more pairs of isolation electrodes on adjacent films below it.

[0026] In some embodiments where a plurality of porous films are stacked, at least one of the isolation electrodes disposed on the first surface of the first porous film is via a conductive path. , Is electrically connected to at least one of the isolation electrodes located on the first surface of the second porous film. In this scheme, the energy storage device can include a three-dimensional extended network of electrode pairs connected in series and / or in parallel over the thickness of the product.

[0027] In some embodiments, the conductive pathway comprises a conductive material in an opening extending through the thickness of the second porous film. The conductive material thereby penetrates through the second porous film and typically communicates electrically with the electrical contacts of the connected electrodes on the first and second porous films. The conductive material may include a curable resin comprising a dispersed metal, preferably a silver-filled epoxy.

[0028] The at least one porous film is typically a polymeric porous film, preferably a flexible polymeric membrane, and thus in flexible electronics applications of capacitive energy storage devices. The possibility of use opens. The thickness of the porous film can be less than 100 microns, preferably less than 50 microns, most preferably less than 30 microns. In general, the volumetric energy density and power density of the device is increased by reducing the film thickness.

[0029] In some embodiments, the flexible polymer membrane comprises a porous material suitable for use as a separator in electrochemical devices such as conventional supercapacitors or lithium ion batteries. In addition to pores, such materials are generally sufficiently chemically stable to avoid deterioration in the presence of acid or alkaline electrolytes and to withstand sudden increases in temperature during operation. It is sufficiently thermally stable. The flexible polymer membrane may comprise at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl chloride, nylon, and polyethylene terephthalate. In certain preferred embodiments, the flexible polymer membrane comprises polyvinylidene fluoride.

[0030] In some embodiments, the capacitive electrode material comprises at least one selected from the group consisting of carbon-based electrode materials or pseudocapacitive electrode materials. In some embodiments, the capacitive electrode material comprises carbon-based electrode materials such as reduced graphene oxide, graphene, exfoliated graphite, porous carbon, and activated carbon. An electrode comprising reduced graphene oxide as a capacitive electrode material, which can be conveniently formed from graphene oxide and subsequently reduced on the surface of the porous film, is particularly preferred. Capacitive electrode materials are generally printed on porous films, as described in more detail later.

[0031] In some embodiments, the electrolyte is a gel electrolyte, optionally cross-linked polyvinyl alcohol, typically strongly acidic or strongly basic, such as KOH, H ₂ SO ₄ , or H ₃ PO ₄ . In combination with an electrolyte salt, it is equipped with. In another example, polyethylene oxide-based gel electrolytes may also be suitable. Gel electrolytes are currently preferred because of their ability to provide energy storage devices that are solid but flexible throughout and the potential to provide augmented ionic conductive pathways between electrodes across the film surface. However, it is also envisioned to use liquid electrolytes that are at least partially retained in the pores of the porous film, including aqueous, non-aqueous, and ionic liquid electrolytes.

[0032] As described herein, a particularly convenient embodiment of the capacitive energy storage device according to the invention has a stacked configuration. Such devices were connected in series and / or in parallel, the microscale size of the electrode pair, the availability of multiple ion conductive paths between the electrodes through the internal pores of the upper and lower porous films. Due to the feasibility for creating a wide variety of three-dimensional expansion networks over the thickness of the electrode pair stack, and the absence of volume-filling components such as current collectors or thick electrolyte layers overlaid on the electrodes. It can have one or more of high energy density and high power density and fast cycling response.

[0033] Accordingly, according to a further aspect, the invention is a stacked capacitive energy storage device: a first porous film; disposed on a first surface of the first porous film. One or more pairs of isolation electrodes, each electrode comprising a capacitive electrode material that communicates ionically with the underlying first porous film; above the first porous film. A second porous film stacked on top of the first porous film, one or more pairs of isolation electrodes located on the first surface of the first porous film is the second porous film. A stacked capacitive energy storage device comprising a second porous film stacked in contact with the back surface of the first and second porous films; and an electrolyte in the internal pores of the first and second porous films. providing.

[0034] Each of the first and second porous films has a first surface and a back surface. When stacked, the back surface of the second porous film faces the first surface of the first porous film and is typically in direct contact with the first surface.

[0035] In some embodiments, the capacitive electrode material has ion communication with the back surface of the second porous film. Therefore, during use, the electrolyte provides ion communication between the isolated electrodes through the internal pores of both the first and second porous films.

[0036] In some embodiments, the stacked capacitive energy storage device is further a pair of one or more isolation electrodes located on the first surface of the second porous film. Each electrode comprises a pair of separated electrodes, each comprising a capacitive electrode material that ionically communicates with a second porous film underneath.

[0037] In some such embodiments, at least one of the isolation electrodes located on the first surface of the first porous film is a second porous through a conductive pathway. It is electrically connected to at least one of the isolation electrodes located on the first surface of the film.

It is understood that other optional or favorable features described herein for embodiments of the capacitive energy storage device of the invention can also be characteristic of embodiments of the stacked capacitive energy storage device. sea bream. Such features include the properties of the porous film, the composition and geometry of the electrode pairs on the first surface of the film, the composition of the electrolyte, and the surface of the film stacked on or adjacent to the same surface. Includes electrical connections between the upper electrode pairs.

[0039] The capacitive energy storage device of the present invention is provided by a method developed by the inventors and for making the device. The methods of the invention form isolated electrodes on the surface of the porous film, including formation at high resolution, such that ion communication between the electrodes is provided at least partially through the internal pores of the porous film. Provide that.

[0040] Accordingly, according to a further aspect, the invention provides a method of making a capacitive energy storage device, the method of which is: a capacitive electrode material or a precursor is applied to the first surface of the porous film. A step of forming one or more pairs of isolation electrodes placed on the first surface; and a step of infiltrating the porous film with an electrolyte, wherein the electrolyte is porous between the isolation electrodes. It provides ion communication through the internal pores of the film.

[0041] In some embodiments, an ink comprising a capacitive electrode material or a precursor material is printed on the first surface. The pores in the film are believed to facilitate the fabrication of microscale electrodes in these preferred embodiments. Although not bound by either theory, the continuous phase of the ink is rapidly sucked into the pores of the film as it is applied, resulting in very small dimensions and narrow electrode-to-electrode distances. It is believed that ink diffusion and coalescence will be prevented even when the electrodes having are printed.

[0042] In some embodiments, the ink is printed on the first surface by gravure printing or flexographic gravure printing, preferably gravure printing. Surprisingly, the inventors have discovered that such a printing technique can be used to print an electrode with micron-scale characteristics on the surface of a porous film conventionally used as a separator. Thereby, excellent resolution and reproducibility can be obtained when an ink having an appropriate viscosity having a dispersed electrode material or a precursor material is adopted. Furthermore, although not bound by any theory, gravure printing results in shear-induced alignment of the electrode material or precursors that form the electrode, thereby allowing favorable ions inside the electrode during the cycle of the energy storage device. It is believed that conductivity will be provided.

[0043] The viscosity of the ink must be in a range suitable for allowing gravure or flexographic gravure printing and limiting or avoiding the penetration of capacitive electrode materials or precursors into the porous film. It doesn't become. Therefore, the ink can have a viscosity between about 25 Pas and about 100 Pas when printed on the first surface. It should be understood that the appropriate concentration of the capacitive electrode material or precursor in the ink for printing the electrodes of the invention will depend on the properties of the material and carrier fluid. In one embodiment, the ink had a concentration between about 1% by weight and 5% by weight of the capacitive electrode material or precursor, such as about 3% by weight.

[0044] In some embodiments, the method of the invention further comprises providing an ink for printing on a first surface. The step of providing the ink may include a step of concentrating a dispersion of the capacitive electrode material or the precursor material to increase its viscosity. In one preferred method, the capacitive electrode material or precursor is dispersed in the aqueous continuous phase of the dispersion, which is: i) to absorb water from the aqueous continuous phase into the absorbent solid. The dispersion is enriched by contacting the dispersion with a water-absorbent solid such as a bead of a superabsorbent polymer; and ii) then separating the dispersion from the water-absorbent solid. The inventors can conveniently prepare a concentrated graphene oxide ink having an appropriate viscosity for gravure printing in this manner, thereby creating a task or diluted dispersion to directly prepare a concentrated graphene oxide dispersion. It was discovered that the problem of enrichment by volatilization of the aqueous phase can be avoided.

[0045] In some embodiments, the separated electrodes formed by applying a capacitive electrode material or pioneer material by the method of the invention have a distance between electrodes of less than about 50 microns, preferably less than 30 microns. .. Moreover, each pair of the separated electrodes formed in this way, including both the electrode itself and the separated area between the electrodes, covers a surface area of less than 1 mm ² on the porous film.

[0046] In some embodiments, the step of applying the capacitive electrode material or pioneer material comprises the step of forming a plurality of pairs of isolated electrodes placed on the first surface of the porous film. Multiple pairs of isolated electrodes are connected in series and / or in parallel by linkages with capacitive electrode materials or precursors. In some embodiments, the step of applying a capacitive electrode material or pioneer material further comprises a step of forming an electrical contact for electrical connection to an external circuit, which also comprises a capacitive electrode. Equipped with materials. Electrodes, linkages, and electrical contacts can be printed on the first surface in the same printing step.

[0047] In some embodiments, for example, an electrode precursor material such as graphene oxide is applied to form an electrode, the method further comprises a capacitive electrode material or a capacitive electrode material on the first surface of the porous film. It has a stage to reduce the pioneer substance and increase its conductivity. Capacitive electrode materials or precursors may be reduced by any suitable technique, including chemical, thermal, photothermal, and beam reduction techniques. In some embodiments, the capacitive electrode material or precursor is reduced by exposure to a chemical reducing agent such as hydroiodic acid.

[0048] In some embodiments, the method is a step of further stacking a plurality of porous films, one of which is a separation electrode disposed on a first surface of the first porous film. One or more pairs are stacked so as to be in contact with the back surface of the second porous film stacked on top of the first porous film, for example by abuttal engagement. There is. It is preferable that the contact provides ion communication between the electrode and the back surface.

[0049] In some such embodiments, the method further comprises at least one of the isolation electrodes located on the first surface of the first porous film via a conductive path. It comprises a step of electrically connecting to at least one of the separation electrodes arranged on the first surface of the second porous film. The step of electrically connecting the electrodes is to penetrate the second porous film and conduct it, for example, by placing a conductive material in an opening extending through the thickness of the second porous film. It has a stage to create a pathway. The conductive material may be printed, drop cast, or injected onto the first surface of the second film and / or into the openings in the second film. In some embodiments, the conductive material comprises a curable resin with a dispersed metal, preferably a resin that can be cured at room temperature, preferably a silver-filled epoxy. Once the curable resin has penetrated through the thickness of the second porous film, the resin may be cured so that the first porous film adheres to the second porous film.

[0050] Accordingly, the method of the invention provides an industrially scaleable stepwise method for making a stacked multi-layer energy storage device using readily available microfabrication techniques. Specifically, the device can be made by stacking a second porous film on top of the first porous film, with a detached electrode arranged on the second porous film. The electrical contacts of at least one of the electrodes are placed in an appropriate vertical alignment with the electrical contacts of at least one of the isolated electrodes located on the first porous film. A curable resin comprising the dispersed metal is then placed through the electrical contacts of the electrodes on the second porous film or into the openings in the second porous film adjacent to the electrical contacts. It is optional to place the curable resin further over the area of the second porous film adjacent to the opening to ensure that a fully conductive connection is made to the electrical contact partner. An opening, which may be a hole with a diameter of less than 1 mm, for example about 0.8 mm, is formed in the second porous film either before or after the step of forming the electrode and the electrical contacts on it. It can be made, but preferably later. The conductive resin penetrates through the opening and contacts the electrical contacts of the electrodes on the first porous film. The resin is then cured to create a permanent electrical connection between the electrodes of adjacent layers of the stack and to bond the layers together. Once all the necessary electrical connections between the electrodes of the first porous film and the electrodes of the second porous film have been made in this manner, the third porous film, as described herein. , Can be stacked on top of the second porous film and electrically connected. In this method, it is possible to produce a multi-layered stack having two layers, three layers, four layers, five layers, or more layers.

[0051] The porous film is optionally saturated with electrolyte before the stacking step, but in some preferred embodiments, the plurality of porous films are after the stacking step. In general, further, only after the step of establishing electrical connections between the layers within the stack, as described herein, is the electrolyte infiltrated. It is an advantage of the present invention that, as a result of the permeable nature of the film of the stacked body, the stacked and electrically connected capacitive energy storage device can be infiltrated with an electrolyte after production. Conceivable.

[0052] In some embodiments, the porous film or a plurality of stacked porous films are infiltrated with a low viscosity curable electrolyte to allow penetration into the device. The curable electrolyte can have a viscosity of less than about 10 Pas, preferably less than about 1 Pas when infiltrated into the film. In such embodiments, the method further comprises the step of curing the low viscosity curable electrolyte to produce a gel electrolyte as soon as the single or more films are properly infiltrated. In some embodiments, the low viscosity curable electrolyte combines crosslinkable polyvinyl alcohol with a strong acid or strong basic electrolyte salt, typically such as KOH, H ₂ SO ₄ , or H ₃ PO ₄ . I have. Such curable electrolytes can be gelled by heat treatment or at room temperature.

[0053] In some embodiments, the porous film to which the capacitive electrode material or pioneer material is applied is a polymeric porous film, preferably a flexible polymeric film. The flexible polymer membrane may include a porous film suitable for use as a separator in electrochemical devices such as conventional supercapacitors or lithium ion batteries. The flexible polymer membrane may comprise at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl chloride, nylon, and polyethylene terephthalate. In certain preferred embodiments, the flexible polymer membrane comprises polyvinylidene fluoride.

[0054] In some embodiments, the capacitive electrode material or pioneer material is at least one selected from the group consisting of carbon-based electrode materials, quasi-capacitive electrode materials, or pioneering materials of either of these. It is equipped with. In some embodiments, the capacitive electrode material or pioneer material comprises graphene oxide.

[0055] In such an embodiment, the method comprises reducing a capacitive electrode material or precursor on the first surface of the porous film to enhance its conductivity. In an embodiment in which graphene oxide is applied to the first surface of a porous film to form an electrode, graphene oxide is reduced, for example, by chemical reduction to produce conductive reduced graphene oxide.

[0056] According to a further aspect, the invention provides a capacitive energy storage device made by any of the methods disclosed herein.
[0057] As disclosed herein, a particularly convenient application of the electrode-functionalized porous film of the invention is the fabrication of stacked multi-layer energy storage devices.

[0058] Therefore, according to a further aspect, the invention is the use of a plurality of porous films, each porous film being disposed on a first surface of the porous film with a first surface. Offering the use of multiple porous films for making capacitive energy storage devices, one or more pairs of isolation electrodes, each comprising a capacitive electrode material that communicates with ions. The use comprises: one or more pairs of isolation electrodes located on the first surface of the first porous film are stacked above the first porous film. A step of stacking a plurality of porous films so as to be in contact with the back surface of the porous film of 2; and a step of infiltrating the porous film with an electrolyte. During charging and discharging of the capacitive energy storage device thus produced, the electrolyte provides ion communication through the internal pores of the porous film between the separating electrodes.

[0059] The contact may be, for example, via a contact engagement. It is preferred to provide ion communication between the electrode whose contacts are located on the first surface of the first porous film and the back surface of the second porous film. During charging and discharging of the capacitive energy storage device thus produced, the electrolyte provides ion communication through the internal pores of the first and second porous films between the separating electrodes.

[0060] In some embodiments, the use further comprises a second, at least one of the isolation electrodes located on the first surface of the first porous film via a conductive pathway. It comprises a step of electrically connecting to at least one of the isolation electrodes located on the first surface of the porous film. In some such embodiments, the step of electrically connecting the electrodes to each other is a conductive material into an opening that extends through the thickness of the second porous film to create a conductive path. It has a stage to install. In some embodiments, after the steps of stacking the porous films and electrically connecting the electrodes to each other, the porous films are infiltrated with an electrolyte.

[0061] The terms "comprise," "comprises," and "comprising" are the specification (including the scope of the claims). When used in, they are one or more other features, individual entities, stages, or components that specify the described features, individual entities, stages, or components. It should be interpreted as not excluding the existence of components, or groups of them.

[0062] In use herein, terms such as "first," "second," and "third" that relate to the various features of the disclosed embodiments are arbitrarily assigned and vary. It is only intended to distinguish between two or more such features that may be incorporated into an embodiment. The terms themselves do not indicate any particular placement orientation or sequence order. Further, the existence of the "first" feature does not imply that the "second" feature exists, and the existence of the "second" feature has the "first" feature. Please understand that it does not imply that.

[0063] Further embodiments of the invention appear in the following detailed description of the invention.
[0064] Here, an embodiment of the invention will be described as an example in association with the accompanying drawings.

[0065] This is a schematic drawing of a conventional supercapacitor configuration reported in the prior art. [0066] A schematic drawing of a pair of separation electrodes printed on a porous film according to an embodiment of the invention. [0067] A side fracture view of the porous film and printed electrode of FIG. 2 taken through the cross section AB indicated in FIG. 2 is drawn. [0068] FIG. 6 is a schematic side view of a single-layer capacitive energy storage device according to an embodiment of the invention, made by infiltrating the porous film of FIG. 3 with an electrolyte. [0069] A schematic drawing of a single-layer capacitive energy storage device with a comb-shaped separation electrode according to an embodiment of the invention in plan view. [0070] A schematic depiction of a single-layer capacitive energy storage device with multiple pairs of comb-shaped electrodes connected in parallel and in series, according to an embodiment of the invention. [0071] A schematic drawing of a side fracture view of two porous films positioned for stacking according to an embodiment of the invention, in which the lower film is printed on the surface of the porous film. It has a pair of separation electrodes. [0072] The porous film of FIG. 7 in which the separation electrodes are stacked so as to be sandwiched between the films is drawn in the side fracture view. [0073] FIG. 6 is a schematic side view of a double layer stacked capacitive energy storage device according to an embodiment of the invention, made by infiltrating the porous film of FIG. 8 with an electrolyte. [0074] According to an embodiment of the invention, it is a schematic depiction of two porous films positioned for stacking in a perspective view, both films being a plurality of comb-shaped electrodes connected in parallel and in series. It has a pair and is about to be dispensed with conductive epoxy to create an electrical connection between the electrode arrays on the two films. [0075] According to an embodiment of the invention, the isolated electrodes of the lower film are stacked so as to be sandwiched between the surfaces of the porous film, and the electrode arrays on the two films are electrically connected with a conductive epoxy. The porous film of FIG. 10, which is stacked in a state of being electrically connected via a portion, is drawn in a perspective view, and further, for stacking on the first and second porous films. A third porous film positioned in is drawn. [0076] According to an embodiment of the present invention, the separating electrodes of the lower two films are stacked so as to be sandwiched between the surfaces of the porous films, and the electrode array on the three films is made of a conductive epoxy. The three porous films of FIG. 11 are drawn in a perspective view, which are stacked in a state of being electrically connected via an electric connection portion. [0077] A multi-layered capacitive energy storage device comprising an array of electrically connected electrode pairs connected in parallel and in series across the thickness of a stack according to an embodiment of the invention. It is a schematic drawing in a perspective view. [0078] FIG. 3 is a side transmission view of the multi-layered capacitive energy storage device of FIG. [0079] An expression of a plate surface design used for producing a plate surface for printing a separation electrode on a porous film surface according to the method of Example 1. [0080] It is a photograph of a plate surface used for printing a separation electrode on the surface of a porous film by the method of Example 1. [0081] A photograph of a porous PVDF film having a graphene oxide electrode printed on its surface, which was produced by the method of Example 1. An array of comb-shaped electrodes printed on the surface of a porous PVDF film according to the method of Example 1 (a) in parallel and (b) connected in series via a linkage of graphene oxide. This is a set of photographs I'm drawing. [0083] An optical microscope image of a pair of printed comb-shaped electrodes on a PVDF film produced by the method of Example 1. [0084] An optical microscope image of a pair of printed electrodes having a zigzag structure on a PVDF film produced by the method of Example 1. [0085] The graph of the point-to-point electrical resistivity of the graphene oxide electrode printed after reduction by a plurality of different reduction procedures is drawn. [0086] It is a photograph of a porous PVDF film having a reduced graphene oxide electrode of hydroiodic acid produced by the method of Example 1. [0088] In the graph of the electrochemical response in the first cycle of the single layer capacitive energy storage device made by the method of Example 1, measured by cyclic voltammetry in Example 2. be. [0089] FIG. 6 is a graph of the electrochemical response over the first 20 cycles of the single layer capacitive energy storage device made by the method of Example 1, measured by cyclic voltammetry in Example 2. [0090] A Nyquist plot of a single-layer capacitive energy storage device as measured by electrochemical impedance spectroscopy in Example 2. [0090-1] The graph of the open circuit potential measurement of the stacked energy storage device in which the electrolyte is infiltrated through the pores of the entire stack, prepared in Example 4, was prepared in Example 5. It is contrasted with a stacked device that simply has an electrolyte layer on top. [0090-2] The electricity of the energy storage device of Example 4, which is stacked, electrically connected, and infiltrated with an electrolyte, over 100 cycles (0V to 0.5V at a scanning speed of 10 mV / s). It is a graph of a chemical response. [0090-3] A Nyquist plot of the stacked energy storage device of Example 4. [0091] Schematic drawing of a plurality of different isolation electrodes made and characterized by the method of Example 3.

[0092] The present invention relates to a capacitive energy storage device, a method for making a capacitive energy storage device, and the use of a porous film for making a stacked capacitive energy storage device. The capacitive energy storage device of the present invention comprises at least one pair of an electrolyte-impregnated porous film and one or more pairs of separating electrodes located on a first surface of the porous film. I have. Each electrode comprises a capacitive electrode material that communicates with the underlying porous film in ions. When used, such as when charging or discharging a device via an external circuit, the electrolyte provides ion communication through the internal pores of the porous film between the isolation electrodes.

Porous film
[0093] The capacitive energy storage device comprises at least one porous film. The thickness of the porous film can be less than 100 microns, preferably less than 50 microns, most preferably less than 30 microns.

[0094] The porous film is typically a polymeric porous film and may comprise at least one selected from the group consisting of polyvinylidene fluoride, polyvinyl chloride, nylon, and polyethylene terephthalate. In certain preferred embodiments, the flexible polymer membrane comprises or consists essentially of polyvinylidene fluoride.

[0095] The pore size of the porous film can be between 0.1 and 0.5 microns, preferably between 0.1 and 0.3 microns, such as approximately 0.2 microns. .. The pore size of the porous film can be measured using a liquid or gas absorption method, such as according to American Society for International Studies (ASTM) D-2873.

Capacitive electrode material
[0096] The separation electrode on the surface of the porous film comprises a capacitive electrode material. The capacitive electrode material can include either or both of a carbon-based electrode material and a pseudo-capacitive electrode material. It should be understood that carbon-based electrode materials that typically have both high surface area (eg, between about 100 m ² / g and 2500 m ² / g) and high conductivity are mainly conductive electrode materials that store energy. It is particularly suitable for electric double-layer capacitors (EDLC devices) caused by the separation of charges within the Helmholtz double layer at the interface between the surface and the electrolyte. In comparison, pseudocapacitive materials store energy through a process of rapid reversible redox or intercalation with electrolyte ions occurring on the surface of the electrode material.

[0097] The capacitive electrode material can include carbon-based electrode materials such as reduced graphene oxide, graphene, exfoliated graphite, porous carbon, and / or activated carbon. An electrode comprising reduced graphene oxide as a capacitive electrode material is particularly preferred because it is conveniently formed from graphene oxide and can subsequently be reduced on the surface of the porous film. Suitable pseudo-capacitive electrode materials include conductive polymers, transition metal oxides, and metal nanoparticles. It is envisioned that the isolated electrode of the present invention can contain both a carbon-based electrode material such as reduced graphene oxide and a pseudo-capacitive material.

Electrolytes
[0098] Capacitive energy storage devices contain electrolytes that have infiltrated into the internal pores of a porous film. The electrolyte may be a liquid electrolyte containing an ionic liquid or an electrolyte comprising an organic solvent and a suitable soluble salt.

[0099] The electrolyte can be a gel electrolyte, eg, an electrolyte comprising a basic polymer such as crosslinked polyvinyl alcohol or polyethylene oxide. Such electrolytes would be particularly suitable for flexible capacitive energy storage devices. The gel electrolyte may comprise a strongly acidic or strongly basic electrolyte salt such as KOH, H ₂ SO ₄ , or H ₃ PO ₄ .

[0100] The invention also relates to a method for making capacitive energy storage devices. The method comprises the step of applying a capacitive electrode material or pioneer material to a first surface of a porous film to form one or more pairs of separated electrodes placed on the first surface. The porous film is infiltrated with the electrolyte so that ion communication is provided between the isolation electrodes through the internal pores of the porous film.

Print the electrodes
[0101] The capacitive electrode material or precursor may be applied to the first surface by any suitable method capable of forming the electrode. In a preferred embodiment, the capacitive electrode material or precursor is applied by printing an ink with the capacitive electrode material or precursor on the surface of the porous film.

[0102] The ink may be printed on the first surface by an intaglio printing technique such as gravure printing. As will be appreciated by those skilled in the art, gravure (or rotary gravure) printing refers to an engraved printed surface, an etched printed surface, or an otherwise microstructured printed surface, such as a printing sheet. A printing method in which ink is applied to a gravure cylinder or a roller-mounted shim. Excess ink is generally wiped off the printed surface and then the printed surface is brought into contact with the substrate. This is typically achieved by feeding the flexible substrate around the coating roller and thus rolling it into contact with the printed surface. The ink in the print surface recess is then transferred to the substrate.

[0103] Gravure printing, and related techniques such as flexographic gravure, are particularly suitable for printing microstructures in high resolution, as they allow the use of viscous inks that do not easily coalesce on the surface of porous films. .. In contrast, techniques such as inkjet printing using low viscosity jetable inks may be suitable for making larger electrodes according to the present invention, but the radial diffuse ion transport mechanism dominates favorably. It may not be very suitable or unsuitable for producing a fine resolution electrode structure. Also, although not bound by any theory, gravure printing is believed to result in favorable shear-induced alignment of the electrode material or pioneer material in the electrode structure.

[0104] The viscosity of the ink is appropriate to allow the formation of high resolution electrode structures by gravure printing and to limit or avoid the penetration of capacitive electrode materials or precursors into the porous film. Must be in the proper range. Suitable ink viscosities include viscosities between about 25 Pas and about 100 Pas.

[0105] Inks with such viscosities may, in some cases, simply disperse a suitable capacitive electrode material or precursor in the carrier fluid at the required concentration, or evaporate the carrier fluid from the diluted dispersion. It may not be easy to obtain just by letting them do it. We have created a sufficiently viscous water-based ink for gravure printing of microelectrodes by contacting a capacitive electrode material or a diluted aqueous dispersion of a pioneer with a water-absorbent solid such as a super-absorbent polymer bead. I discovered that I can provide. The water-absorbent solid can absorb water from the aqueous continuous phase and then be separated from the residual concentrated viscous dispersion.

[0106] By gravure printing the electrodes with a graphene oxide-containing ink of suitable viscosity prepared in this manner, the electrodes have a line width of approximately 50 microns and the electrodes have a separation distance of less than 30 microns and are porous. An electrode pair, which covers a surface area of less than 1 mm ² on a film, can be made.

[0107] Electrodes with a wide variety of geometric shapes can be printed according to the invention. Suitable electrode-to-geometric shapes include combs, pads (rectangles), concentric circles, zigzags, L-shapes, and labyrinthine geometries, as depicted in FIG.

[0108] It should be understood that the gravure printing of microelectrodes according to the invention is further processed via web processing, i.e., a continuous web of flexible porous film from a feed roll via a printing station. It is convenient to be able to modify it to scale up for and / or by feeding it onto a take-up roll.

Reduce the electrode
[0109] In the method of the invention, either a capacitive electrode material or a precursor thereof can be applied to the first surface to form an electrode, optionally further linking between the electrode pair and the electrical contact. Can be formed. In use here, the pioneering material of the capacitive electrode material is a material that can be converted into a conductive capacitive electrode material on a porous film substrate by appropriate chemical conversion. Thus, when the pioneer material is applied to the surface of the porous film, for example by printing an ink with the pioneer material onto the surface of the porous film, the method of the invention applies the pioneer material material on the surface of the porous film to the capacitive electrode. Includes the steps of converting to material.

[0110] In a preferred embodiment, the precursor material is reduced to form a capacitive electrode material. The precursor may be reduced by any suitable technique, including chemical, thermal, photothermal, or beam methods. Suitable reduction methods for making various capacitive electrode materials from their precursors have been reported and are available to those of skill in the art.

[0111] Graphene oxide is a particularly suitable capacitive electrode material pioneer because it is believed that it can be more easily dispersed in water-based inks than reduced high surface area carbon materials such as graphene. Therefore, the separation electrode of the present invention can be printed using graphene oxide-based ink, and then the printed graphene oxide can be reduced in the printed electrode to form reduced graphene oxide. The reduced graphene oxide has a high surface area and electrical conductivity suitable for use in the capacitive energy storage device according to the present invention. Graphene oxide can be reduced on the surface of the porous film by methods including chemical, thermal, photothermal, and beam reduction techniques. For example, the graphene oxide printed electrode can be reduced by exposure to a chemical reducing agent such as hydrazine or hydroiodic acid.

Infiltrate the film with electrolyte
[0112] In the method of the invention, the porous film is infiltrated with an electrolyte. In a preferred embodiment, the porous electrode material or pioneer material is applied to form an electrode on the porous film, and then the porous film is wetted with an electrolyte. However, it does not preclude that electrodes can also be formed on a porous film that has already been moistened with an electrolyte or one or more components thereof or a precursor thereof.

[0113] The electrolyte is at least partially infiltrated into the internal pores of the one or more porous films. As such, it is generally preferred to infiltrate the low viscosity liquid electrolyte or pioneer mixture into the porous film, thereby allowing permeation into the film. In this way, a liquid phase electrolyte such as an ionic liquid electrolyte or an organic solvent-based electrolyte can be infiltrated directly into the porous film, for example, by applying the electrolyte to the surface of the porous film. If a gel electrolyte is preferred, a low viscosity electrolyte precursor may be used to enable infiltration into the internal pores of the film, followed by gelling the precursor to produce the electrolyte. good. The low-viscosity electrolyte pioneer may include a crosslinkable polymer such as polyvinyl alcohol in an aqueous mixture that also contains electrolyte ions. In that case, the gel electrolyte is produced by cross-linking the polymer.

Embodiment as an example
[0114] FIG. 1 schematically depicts a prior art supercapacitor 100 with metal current collector foils 101 and 102 connected to an external circuit. The current collector foils 101 and 102 are covered with high surface area conductive carbon electrodes 103 and 104. The porous separator 105 placed in between provides electrical insulation between the electrodes, while the separator 105 and the electrolyte 106 that saturates the electrodes 103 and 104 provide ion communication between the electrodes during charging and discharging. do. The separation distance between the electrodes (denoted as _ds in FIG. 1) is greater than the thickness of the separator and therefore typically greater than 50 microns. Moreover, the electrodes can only be reached from a single direction during charging and discharging of the device, i.e., an ion conductive path extending directly between the electrodes 103 and 104 through the separator 106 (indicated by arrow 106). ) Can only be reached. In addition, the relatively large size of the electrodes 103 and 104 forces the use of current collector foils 101 and 102 to avoid unacceptable internal electrode resistance.

[0115] Hereinafter, certain embodiments of the present invention will be described with reference to FIGS. 2 to 4 in particular. FIG. 2 schematically illustrates a fracture surface of a capacitive energy storage device 200 comprising a porous PVDF film 201 and a pair of isolation electrodes 202 and 203. The electrodes 202 and 203 are rectangular in shape and have a separation distance of less than 30 microns (denoted as _ds in FIG. 2). Electrodes 202 and 203 are connected to electrical contact pads 204 and 205 via linkages 206 and 207, respectively, which contacts can be used, for example, for electrical connections to external circuits via attached wires. The electrodes, linkages, and contact pads are reduced produced by printing an ink containing graphene oxide onto the porous film 201 and then chemically reducing the graphene oxide, as described in more detail below. It is equipped with graphene oxide.

[0116] FIG. 3 schematically depicts a capacitive energy storage device 200 taken through the AB cross section indicated in FIG. 2 in a side view. The porous film 201 has a first surface 208 and a back surface 209, and has a thickness of approximately 50 microns (denoted as _ts in FIG. 3). The electrodes 202 and 203 are arranged directly on the first surface 208 without the intervention of a metal current collector layer and have an out-of-plane thickness of approximately 50 nm ( _denoted as t). As depicted in FIGS. 3 and 4, polyvinyl alcohol / KOH electrolyte 210 is applied from the dispenser 211 to the porous film 201 as a low viscosity aqueous mixture, thereby filling the internal pores 212 of the porous film 201. Optionally, a layer 213 is further formed on the first surface of the porous film. The electrolyte 210 is then gelled by heat treatment to provide the gel electrolyte in the internal pores of the film 201 and in the layer 213.

[0117] The high surface area reduced graphene oxide of the electrodes 202 and 203 is in direct contact with the lower portion of the first surface 208 of the porous film 201 and thus in ion communication with the first surface 208. During use, when a potential is applied across the isolation electrodes 202 and 203 to charge the energy storage device, or when the device is discharged via an external circuit, the electrolyte in the internal pores is indicated by arrow 214 in FIG. Provides a path for ion communication between electrodes as depicted in. Optionally, an augmented path for ion communication is also provided through layer 213 above the first surface 2018, as depicted by arrow 215. However, the internal pores 212 serve as the main reservoir for the electrolyte 210, and in particular provide an ion transport path through multiple directions between the capacitive reduced graphene oxide materials of the electrodes 202 and 203.

[0118] From this, the fracture surface of the capacitive energy storage device 300 including the porous PVDF film 301 infiltrated with an electrolyte (not shown) and the pair of the separation electrodes 302 and 303 is schematically shown in a plan view. Another embodiment of the invention will be described with reference to FIG. 5 drawn. Electrodes 302 and 303 include reduced graphene oxide, one printed directly on the surface of the porous film as graphene oxide and chemically reduced there. The plurality of electrodes integrally form a pair of comb-shaped electrodes, and each electrode has four fingers. Fingers have a width of 100 microns (denoted as w _f in FIG. 5) and a length of 900 microns (denoted as L _f in FIG. 5). The separation distance between the electrodes (denoted as _ds in FIG. 5), that is, the shortest distance between adjacent fingers is approximately 30-50 microns. The pair of separated electrodes ₃₀₂ and 303 containing the electrode itself and the separated area between the electrodes is calculated as the product of the electrode pair width and the electrode pair length (shown as we and _Le in FIG. 5, respectively). It covers the surface area on a porous film of less than 1 mm ² .

[0119] Hereinafter, another embodiment of the invention will be described with reference to FIG. 6, which depicts the capacitive energy storage device 400. A plurality of pairs of separation electrodes 402 and 403 (shown as 402a / 403a to 402d / 403d in FIG. 6) are arranged on the first surface 408 of the porous PVDF film 401. The film 401 is infiltrated with an electrolyte (not shown). Electrodes 402 and 403 include reduced graphene oxide, reduced graphene oxide that is printed directly onto the surface of the porous film and chemically reduced there, and ionically communicates with the surface 408. ing.

[0120] The capacitive energy storage device 400 comprises parallel electrode pairs (ie, 402a / 403a in parallel with 402b / 403b and 402c / 403c in parallel with 402d / 403d). Also, the capacitive energy storage device 400 comprises a pair of electrodes connected in series (ie, a combination of 402a / 403a and 402b / 403b connected in series with a combination of 402c / 403c and 402d / 403d). ing. The array of plurality of electrode pairs is electrically connected by a conductive linkage 406 of printed reduced reduced graphene oxide on the first surface 408 of the porous film 401. The electrically connected array of electrode pairs is further provided with electrical contact pads 404 and 405, which are also composed of printed and reduced graphene oxide, respectively. The array of electrodes can be electrically connected to an external circuit via wires 416 and 417 attached to contact pads 404 and 405, respectively.

[0121] Capacitive energy storage devices 400 are depicted in the case where two blocks of two parallel connected electrode pairs are connected in series, but a wide variety of electrode configurations can be provided according to the same invention. It will be understood that.

[0122] From this, another embodiment of the invention will be described with reference to FIGS. 7 to 9. FIG. 7 is a side view of a first porous PVDF film 501a having a pair of separation electrodes 502 and 503 placed directly on the first surface 508a. The electrodes 502 and 503 can be connected to an external circuit via a contact pad (not shown) with attached wires. As depicted in FIGS. 7 and 8, the second porous PVDF film 501b is then on top of the first porous film 501a, and the electrodes 502 and 503 are on the back surface 509b of the second porous film 501b. It is stacked so as to abut and engage with. Since both the first porous film and the second porous film are flexible films, the films 501a and 501b fit closely around the electrodes 502 and 503 so that the surfaces 508a and 509b are in contact. At most, a small gap 519 remains around the electrode.

[0123] As depicted in FIGS. 8 and 9, the stacked porous films 501a and 501b are then coated with polyvinyl alcohol / KOH electrolyte 510 as a low viscosity aqueous mixture from the dispenser 511. Thereby, the internal pores 512a of the porous film 501a and the internal pores 512b (and the gaps 519 if present) of the porous film 201b are filled. The electrolyte 210 is then gelled by heat treatment to provide the gel electrolyte in the internal pores of both films 501a and 501b. Thus, the stacked capacitive energy storage device 500 is depicted in FIG.

[0124] The high surface area reduced graphene oxide of the electrodes 502 and 503 is in direct contact with the back surface 208a of the first surface 208a of the porous film 501a and the back surface 509b of the second porous film 501b, and thus ion-communicate. During use, when a potential is applied across the isolation electrodes 502 and 503 to charge the energy storage device, or when the device is discharged via an external circuit, the electrolytes in the internal pores of both films are shown in the figure. 9 provides a path for ion communication between the electrodes, as depicted by arrows 514a and 514b. All surfaces of the electrodes 502 and 503 are effectively surrounded by a pool of electrolyte contained substantially throughout in the internal pores of the first porous film 501a and the second porous film 501b. It provides an ion transport path through multiple directions between the capacitive reduced graphene oxide materials of the electrodes 502 and 503, yet avoids dead volume in the device occupied by the electrolyte layer. ..

[0125] From now on, another embodiment of the invention will be described with reference to FIGS. 10 to 14. FIG. 10 depicts a first porous PVDF film 601a and a second porous PVDF film 601b, each of which is a plurality of separation electrodes 602 and 603 disposed on the first surfaces 608a and 608b. It has a pair (including 602a / 603a and 602b / 603b, respectively). Electrodes 602 and 603 include reduced graphene oxide and are connected via conductive linkages 606a and 606b, as described herein in connection with FIG. 6, with electrical contact pads 604a and 605a as well. 604b and 605b are provided, respectively. The contact pad 604a can be electrically connected to an external circuit via the attached wire 616.

[0126] As depicted in FIGS. 10 and 11, a second porous PVDF film 601b is described in more detail here on top of the first porous film 601a in connection with FIG. As such, the electrodes 602a and 603a are stacked so as to abut and engage with the back surface 609b of the second porous film 601b. The films are stacked so that the contact pads 605b are aligned vertically with the contact pads 605a. The conductive silver particle-filled epoxy resin 618 dispensed from the dispenser 619 is then installed in the opening 620b and on the area adjacent to the contact pad 605b. The opening 620b is a hole that penetrates the entire thickness of the contact pad 605b and the second porous film 601b. With the films stacked, the conductive epoxy 618 penetrates through the opening 620b and contacts the contact pad 605a on the first porous film 601a. The epoxy 618 is then cured to create a permanent electrical connection 621a-621b between the contact pads 605a and 605b and to permanently bond the porous films 601a and 601b together.

[0127] It should be understood that the opening 620b may be formed either before or after the step of printing the contact pad 605b on the first surface 608b, and further the porous film 601b is porous. It may be formed either before or after the step of stacking on the film 601a. Similarly, it should be understood that the opening 620b does not necessarily have to penetrate the contact pad 605b in a straight line, for example, when the epoxy 618 is applied, it spreads over the surface 608b onto the contact pad 605b. It may be positioned adjacent to the contact pad 605b so as to go. Also, the contact pads 605b and 605a do not have to be the same size or perfectly vertically aligned. As will be appreciated by those skilled in the art, the contact pads 605a and 605b and the openings 620b may be configured differently provided that appropriate electrical connections between the contact pads can be provided.

[0128] Other means of electrically connecting the contact pads 605a and 605b that do not rely on the openings formed in the film are also considered to fall within the invention. For example, a conductive material of sufficiently low viscosity may be applied to the first surface 608b on and / or adjacent to the contact pad 605b, and the internal pores of the porous film 601b to create electrical connections. It may be made possible to pass through the contact pad 605a so as to come into contact with the contact pad 605a. Alternatively, electrical connections may be provided via metal wires or clips that extend around the edges of the porous film 601b.

[0129] As depicted in FIGS. 11 and 12, a third porous PVDF film 601c with a plurality of pairs of electrodes containing 602c / 603c placed on the first surface 608c is then the third. The electrodes 602b and 603b are stacked on the porous film 601b of 2 so as to abut and engage with the back surface 609c of the third porous film 601c. The conductive epoxy resin 618 is then infiltrated through the opening 620c to create an electrical connection between the contact pads 604c and 604b, 621b-621c. The contact pad 605c can be electrically connected to an external circuit via the attached wire 617.

[0130] As depicted in FIGS. 12 and 13, polyvinyl alcohol / KOH electrolyte 610 is then applied to the porous films 601a, 601b, and 601c stacked from the dispenser 611 as a low viscosity aqueous mixture. , Thereby infiltrating the entire stack including the internal pores 612 of all three porous films. The electrolyte 610 is then gelled by heat treatment to provide the gel electrolyte into the internal pores of the films 601a, 601b, and 601c. Thus, the stacked capacitive energy storage device 600 is depicted in FIG.

[0131] FIG. 14 depicts a side perspective view of a capacitive energy storage device 600 comprising stacked porous films 601a, 601b, and 601c and electrode pairs 602 and 603 on each film. The electrode pairs 602a / 603a and 602b / 603b are sandwiched between the films 601a and 601b and between the films 601b and 601c, respectively. A cured conductive epoxy electrical connection 621a-621b penetrates the thickness of the film 601b and thus electrically connects the contact pads 605b and 605a as described herein. Similarly, the electrical connection portions 621b-621c penetrate the thickness of the film 601c and thus connect the contact pads 604c and 604b to the electrical body. The gelled electrolyte 610 is infiltrated through the entire stack and is located primarily within the internal pores 612 of each of the porous films 601a, 601b, and 601c. The entire electrochemical storage device is isolated in a Kapton polyimide pouch 621 with only wires 616 and 617 protruding for connection to external circuits. .. It is noteworthy that the stacked device 600 is flexible throughout the device, thanks to the fact that it is constructed from multiple layers of flexible polymer membranes and is completely encapsulated within a flexible pouch.

[0132] The high surface area reduced reduced graphene of the paired electrodes 602a / 603a is sandwiched between the porous films 601a and 601b, and thus ionically communicates with both porous films, while the paired electrodes. The reduced graphene oxide of 602b / 603b is sandwiched between the porous films 601b and 601c, and thus ionically communicates with both porous films. In use, when a potential is applied across a connected array of electrode pairs extending across all three layers of the stack to charge the device 600, or the device 600 (via wires 616 and 617). When discharged through an external circuit, the electrolyte in the internal pores of the porous film provides a path for ion communication between the pairs of electrodes.

[0133] FIGS. 13 and 14 depict a stacked capacitive energy storage device 600 with three layers of porous film and electrodes, but with four, five, or even more layers. It will be understood that layered weights can be made by the same methodology. Further, although the device 600 is depicted as having only one electrical connection between adjacent layers, the multi-layer stack is similarly designed to have a plurality of electrical connections between the electrodes of the adjacent layers. You can also. For example, pairs of electrodes on adjacent layers may be connected in parallel by electrically connecting one electrode of each pair to the corresponding electrode on the adjacent layer side.

[0134] The present invention will be described in the context of the following examples. It should be understood that the examples illustrate the inventions described herein and are not intended to be limited to the inventions described herein.

material
[0135] Large flake natural graphite was added to Strategic Energy Resources Pty Ltd. Obtained from the company. Potassium hydroxide (KOH), polyvinyl alcohol (PVA), acetonitrile, hydrogen iodide, acetic acid, sulfuric acid, potassium persulfate, phosphorus pentoxide, potassium permanganate, ammonia (NH ₄ OH), and hydrazine, Sigma Aldrich Purchased from the company and used without any further purification. A cross-linked polyacrylic acid copolymer-based hydrogel bead capable of absorbing 90 times its own weight of water was prepared by Demi Co Ltd. Obtained from the company (China). A flexible and porous PVDF membrane (~ 50 micron thick and 0.2 micron pore size) was prepared by mdi Technologies Pty Ltd. Purchased from the company (India). A non-porous cellulose acetate sheet (Nobo Universal transparency sheet) was obtained from an office supply retailer. Electrically conductive epoxy was used by AgIC Inc. of Japan. AgIC is at least a registered trademark of Agic Co., Ltd. in Japan, and AgIC is a registered trademark of Elephantech Inc. (former name: AgIC Co., Ltd.) in Japan. Is a separate corporation, and this description seems to refer to the latter). The Kapton polyimide sheet was purchased from DuPont.

Example 1. Preparation of single-layer capacitive energy storage device 1a) Synthesis of graphene oxide
[0136] Graphene oxide (GO) was synthesized using the modified Hammers method. Large flake graphite, sulfuric acid, potassium persulfate, phosphorus pentoxide, and potassium permanganate were used for the synthesis. The synthesized GO was exfoliated in reverse osmosis purified water by ultrasonic treatment (UP-100 sonication apparatus) for 1 hour, and then centrifugation was performed to remove unexfoliated crystals of GO.

1b) Preparation of GO ink
[0137] A dispersion in which GO was dispersed in water at a GO concentration of 0.25 mg / ml was prepared as described above. To 1 liter of dispersion sample, 10 g of superabsorbent polymer (SAP) bead was added. After 1 hour, the saturated beads were separated from the remaining dispersion, washed with water and dried at 50 ° C. for reuse. The concentrated dispersion after bead removal had a volume of 10 ml at a GO concentration of 30 mg / ml. The viscosity of the ink was 25 Pas.

1c) Gravure printing of graphene oxide microelectrode
[0138] GO ink was printed on a flexible porous polyvinylidene fluoride (PVDF) film using a gravure printing device (Labrator 180 obtained from nsm Norbert Schlavli Machinen, Switzerland). Plates with various sizes of comb-shaped electrode patterns and an array of interconnected electrode patterns in various combinations of series and parallel configurations were designed. The plate surface was etched with a laser procured from Norbert Schrafli AG of Switzerland. An example of the plate design is drawn in FIG. 15, and a photograph of the etched plate is drawn in FIG.

[0139] GO ink was applied to the plate surface. Then, the flexible PVDF film wound around the coating roller was rolled into contact with the flat plate surface, and the separation electrode was printed on the surface of the PVDF film. The printed electrodes were dried within a few minutes under atmospheric conditions.

[0140] Examples of a porous PVDF film having a separable comb-shaped GO electrode placed on the surface are depicted in FIGS. 17 and 18. In FIG. 17, a wide variety of series and / or parallel electrode pairs are made by the printing process, including blocks in which multiple electrode pairs in parallel, multiple electrode pairs in series, and electrode pairs in parallel are connected in series. You can see that you did. The isolated electrode pairs in the array are connected by a linkage of graphene oxide on the surface of the PVDF film, and each connected array of isolated electrode pairs further has two rectangular graphene oxide contact pads.

[0141] FIG. 18 (a) shows an enlarged view of an array consisting of four pairs of comb-shaped separation electrodes connected in parallel, and FIG. 18 (b) shows a comb-shaped separation electrode 4 connected in series. An enlarged view of the paired array can be seen. Each pair of electrodes has two comb-shaped electrodes, each electrode having four fingers with a width of approximately 90 microns and a length of approximately 890 microns. The extraplanar thickness of the electrode was approximately 50 nm. The electrode separation distance, that is, the separation distance between the fingers of the comb-shaped electrode is approximately 100 microns. Each pair of comb-shaped electrodes, including both the electrode and the inter-electrode separation area, covers a surface area of approximately 9 mm ² on the surface of the porous PVDF film. The graphene oxide contact pad is 2 mm x 2 mm square to facilitate electrical connection to external circuits.

[0142] Thus, printed electrode pairs with various different dimensions were made. FIG. 19 depicts an optical microscope image of a pair of printed comb-shaped electrodes on a PVDF film. The finger width of each electrode is approximately 100 microns, and the separation distance between the electrodes is approximately 40 microns. The electrode pair covers a surface area of less than 2 mm ² on the surface of the porous PVDF film.

[0143] FIG. 20 depicts an optical microscope image of a pair of printed electrodes on a PVDF film, the electrodes having a zigzag configuration. The separation distance between the electrodes is approximately 30 microns, and the electrode pair covers a surface area of less than 0.25 mm ² on the surface of the porous PVDF film. The printed electrical linkage that connects the electrodes to the electrical contact pads has a line width of approximately 30 microns. Therefore, for example, it is considered that a comb-shaped electrode having a finger width of less than about 30 microns and a separation distance between electrodes below about 30 microns can be produced by this method.

[0144] The various different arrays of electrode pair combinations depicted in FIG. 17 were made on the substrate for research purposes, and in commercial embodiments, the configuration of the printed electrodes on the porous substrate is of the device. It will be understood that it will be made according to energy storage requirements and from the perspective of minimizing unused space on the film surface.

1d) Reduction of microelectrode
[0145] Multiple chemical reduction methodologies are used to reduce printed GO microelectrodes on porous PVDF films with the aim of maximizing conductivity and thereby minimizing resistance-related losses in printed supercapacitors. bottom.

[0146] In the first reduction procedure (hydrazine and ammonia solution reduction), a PVDF film with a printed GO microelectrode was loaded with 0.15 ml of hydrazine (80 wt%) and 1.05 ml of NH ₄ OH (0. It was immersed in a mixed solution of 28% by weight) and 300 ml of water, and heated under a water-cooled condenser at 95 ° C. for 1 hour. After 1 hour, the film was thoroughly washed with water and methanol and dried in a vacuum oven at 145 ° C. for 1 hour.

[0147] In the second reduction procedure (hydrazine vapor phase reduction), a PVDF film with a printed GO microelectrode was placed on the wall of a 100 ml beaker using Kapton tape. 1 ml of hydrazine (80 wt%) was added to the beaker, followed by covering the beaker with parafilm and heating at 100 ° C. for 16 hours. Subsequently, the film was thoroughly washed with water and methanol and dried in a vacuum oven at 145 ° C. for 1 hour.

[0148] In the third reduction procedure (thermal reduction), the PVDF film with the printed GO microelectrode was heated under vacuum at 150 ° C. (below the melting temperature of the PVDF substrate 170 ° C.) for 6 hours.

[0149] In the fourth reduction procedure (hydrazine solution reduction), a PVDF film with a printed GO microelectrode is immersed in a mixed solution of 1 ml hydrazine (80 wt%) and 100 ml water and cooled and condensed. It was heated under a vessel at 100 ° C. for 24 hours. Subsequently, the film was thoroughly washed with water and methanol and dried in a vacuum oven at 145 ° C. for 1 hour.

[0150] In the fifth reduction procedure (hydrogen iodide reduction), a PVDF film with a printed GO microelectrode was placed on the wall of a 300 ml beaker using Kapton tape. 2 ml of hydroiodic acid (55 wt%) and 5 ml of acetic acid were added to the beaker. The beaker was covered with parafilm and heated at 40 ° C. for 16 hours. Subsequently, the film was thoroughly washed with water and methanol and dried under atmospheric conditions.

[0151] Wire the Agilent B2900 series precision source / measure unit through the EmCal Generyte probe station to a tungsten probe with a 5 micron tip. It was used and a two-point conductivity measurement was performed. The probe was placed on the 2 mm × 2 mm contact pad of the electrode with a distance of 1 mm. Measured values were taken by varying the applied voltage between 0V and 1V. The scanning speed used for the measurement was 0.8 V / s, and the measured values were taken every 0.008 V.

[0152] The resistivity of the printed graphene oxide after reduction by one of the first to fifth reduction procedures is shown in FIG. The highest resistivity was observed for the thermally reduced and printed GO (10 kmΩm), which was comparable to the resistivity of the GO at the time of printing. The lowest resistivity (approximately 20 Ωm) was observed in the case of hydrogen iodide reduction, and therefore it was used in subsequent electrochemical characterization studies.

[0153] FIG. 22 depicts a porous PVDF film in which a plurality of pairs of comb-shaped reduced graphene oxide electrodes are placed on the surface of the film. A clear color change of graphene oxide from brown (unreduced) to black (reduced) was evident. The reduction process did not degrade the printed configuration of the electrodes.

1e) Cell assembly and electrolyte infiltration
[0154] A thin line of wax (generally with a width in the range of 1 mm-1.5 mm) was deposited between the printed and reduced electrodes and the contact pads of the electrodes on a porous film. This locally penetrated the pores of the film and closed the pores prior to the stage of solidifying the contact pad, thus isolating the contact pad from the electrolyte. An electrolyte mixture was prepared by adding polyvinyl alcohol (PVA, 1 g) to deionized (DI) water (10 ml) and the mixture was heated at 90 ° C. with constant stirring. Once the PVA / aqueous solution became clear, KOH (10 ml 6M solution) was added dropwise until a homogeneous solution was achieved. Subsequently, the electrolyte mixture was cooled to room temperature. The porous film was then infiltrated with a low viscosity PVA / KOH electrolyte mixture qualitatively having the same viscosity as glycerin and thus estimated to be about 1 Pas. Infiltration was performed by dropping the electrolyte onto the porous film until saturated; the uncured electrolyte mixture was visible in the film until a visible electrolyte layer was formed on the surface. It was absorbed. After the film was infiltrated with the electrolyte premix, the electrode / electrolyte assembly was left at room temperature for 24 hours to promote the gelation of the electrolyte inside the pores of the film. The cell was then sealed in a pouch of Kapton sheet. A small alligator clip with metal wires attached is sandwiched between a pair of comb-shaped reduced graphene oxide electrodes on the surface of a porous PVDF film or to the electrical contact pad side of a pair of electrically connected arrays. Attached, the electrochemical responses of various devices were measured.

Example 2. Electrochemical evaluation of single-layer capacitive energy storage devices
[0155] The electrochemical response of the capacitive energy storage device made by the method of Example 1 is characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using Biologic's VSS potentiostat. Attached.

[0156] Open circuit potential measurements were performed over an hour prior to each electrochemical test to ensure stable electrochemical conditions. If the fluctuation of the open circuit potential of less than 10 mV persisted for a period of 1000 seconds, it was considered to be a stable electrochemical condition. The CV test was performed between 0V and 0.5V at a scanning speed of 10 mV / s and repeated over approximately 100 cycles. The EIS test was performed by applying a sine and cosine potential wave at an open circuit potential with an amplitude of 10 mV. Impedance responses were measured over frequencies between 1 MHz and 10 MHz and 6 points were recorded per decade of frequency.

[0157] CV response of a single pair of printed and reduced comb-shaped electrodes (4 fingers, finger width approximately 90 microns, finger length approximately 890 microns, extraplanar thickness approximately 50 nm, electrode separation distance approximately 100 microns). Is approximately rectangular, suggesting ideal capacitive behavior and low internal resistance, as depicted in FIG. The energy storage capacity of the device increased slightly over the first 20 cycles and then remained substantially unchanged over the additional 80 cycles, as depicted in FIG. The specific capacitance of the single-electrode vs. capacitive energy storage device was calculated to be approximately 3 mF / cm ² , further demonstrating a high cycleability of 10 mV / s.

[0158] Consistent with the CV response, the single electrode vs. device Nyquist plot also exhibits excellent capacitive behavior, as shown in FIG. The equivalent series resistance was calculated to be 8Ωcm ² .

Example 3. Comparative example
[0159] The graphene oxide ink prepared according to the procedure of Example 1a) -1b) was printed on the flexible polymer film according to the procedure of Example 1c). As described in Example 1, high resolution isolated electrode pairs with well-defined features of less than about 30 microns could be printed on a porous PVDF film. In contrast, printing of comb-shaped electrodes was unsuccessful with non-porous cellulose acetate film. The ink coalesced on the surface, causing a complete loss of the printed depiction. Therefore, it is determined that the suction of the aqueous phase ink into the pores of the PVDF film during printing contributes to the high resolution of the various characteristics of the electrode to be realized.

Example 4. Preparation of Stacked Capacitive Energy Storage Devices 4a) Multi-layer stacking and electrical connection
[0160] Three porous PVDF films, each having a pair of comb-shaped reduced graphene oxide electrodes, were prepared by the method of Examples 1a) -1d). The electrode pair was equipped with four finger electrodes having a finger width of approximately 90 microns, a finger length of approximately 1800 microns, an out-of-plane thickness of approximately 50 nm, and an inter-electrode separation distance of approximately 200 microns. Each electrode was connected to a reduced graphene oxide contact pad (2 mm x 2 mm) on the film surface. A wax coating was deposited between each electrode and the contact pad as described in Example 1e). A precision hole puncher with a diameter of 0.8 mm was then used to penetrate the electrical contact pads of each layer and the underlying film to create precision holes with a diameter of 0.8 mm.

[0161] The three layers were then stacked directly on top of each other with the holes in each layer aligned vertically. Next, a highly conductive epoxy adhesive containing silver nanoparticles and having a paste-like consistency was previously stacked on the electrical contacts of the electrodes using a syringe with a 0.5 mm needle opening. The injection was made through the holes and the epoxy was brought into contact with the electrical contact pads of each layer. After deposition, the epoxy adhesive was cured at room temperature for 24 hours. The establishment of electrical connections through the three board layers was confirmed using a digital multimeter. As a result of the electrical connection, the electrode pairs on each layer were electrically connected in parallel.

4b) Cell assembly and electrolyte infiltration
[0162] Polyvinyl alcohol (PVA, 3 g) was mixed in deionized water (30 ml) and H ₂ SO ₄ (98%, 3 g) was added dropwise to prepare an electrolyte mixture. The mixture (8.33 wt% PVA) was heated to 85 ° C. with active stirring for 1 hour and cooled to room temperature. The low viscosity electrolyte mixture was then drop cast onto a stack of porous films and subsequently dried under atmospheric conditions for 24 hours. The infiltration of the electrolyte in the three-layer stack was visually observable because the entire stack became transparent. The cell was then sealed in a pouch of Kapton sheet. Two small alligator clips with metal wires were then sandwiched towards the stack and the electrochemical response of the stacked energy storage device was measured. Each clip was electrically connected to one electrode on each layer via an electrical contact pad on the top layer and a conductive epoxy connection between the layers.

Example 5. (Comparative example)
[0163] A three-layer stacked device was prepared according to the method of Example 4a.
[0164] Polyvinyl alcohol (PVA, 3 g) was mixed in deionized water (30 ml) and H ₂ SO ₄ (98%, 3 g) was added dropwise to prepare an electrolyte mixture. The mixture (8.33% by weight PVA) was heated to 85 ° C. with active stirring for 1 hour, poured into a Petri dish as a film, and dried at 80 ° C. for 8 hours. The gelled film was then removed from the Petri dish, manually placed over the top layer of the stack, and pressed onto the stack via polyimide tape. Thus, the porous film of the stack was placed in ion communication with the electrode pair on the stack, with the electrolyte layer on top but not infiltrated. The cell was sealed in a pouch of a Kapton sheet as described in Example 4b) and an alligator clip was attached.

Example 6. Electrochemical evaluation of stacked capacitive energy storage devices
[0165] The electrochemical response of the stacked capacitive energy storage device made according to the methods of Examples 4 and 5 is electrochemical impedance using cyclic voltammetry (CV) and Biologic's VSS potentiostat. Characterized by spectroscopy (EIS).

[0166] In order to investigate the effect of electrolyte infiltration through the three porous film layers in the stack, open circuit potential measurements were first performed as described in Example 2. As is evident in FIG. 26, the stacked energy storage device (prepared in Example 4) with the electrolyte infiltrated through the pores of the entire stack was stable with very low variability (up to 30 mV vs SHE). Provided an open circuit potential. In contrast, large voltage fluctuations (600 mV-1.8 V vs SHE range) were obtained for stacked devices (prepared in Example 5) with only an electrolyte layer mounted on top. This result demonstrates the importance of electrolyte infiltration into the pores of the porous film of the electrochemical storage device according to the invention.

[0167] The CV response of the stacked, electrically connected, and electrolyte infiltrated energy storage device of Example 4 over 100 cycles (0V to 0.5V at a scanning rate of 10 mV / s). It is shown in FIG. The energy storage capacity of the device increased slightly over the first 20 cycles and then remained substantially unchanged over the additional 80 cycles. The CV plot is roughly rectangular, suggesting the capacitive behavior of the stacked device configuration.

[0168] A Nyquist plot of a stacked energy storage device (Example 4) is shown in FIG. The relatively high resistance (compared to that of the single-layer device depicted in FIG. 25) may be due to the conductive epoxy connections established between the electrical contact pads on the three layers.

Example 7. Electrode configuration
[0169] In this example, the electrochemical performance of a plurality of different capacitive microelectrode geometries is investigated. The microelectrodes were not made according to the present invention; however, learning about the effect of geometric shapes on electrode performance could be used to guide the design of capacitive energy storage devices according to the present invention.

[0170] A continuous graphene oxide layer (0.6 micron thick with a rms roughness of 2.0 nm ± 0.4 nm) was spin coated onto a silicon wafer. Attach the wafer to the SEM stub with double-sided carbon tape and place it into the chamber of the FEI Helios Nanolab 600 FIB-SEM and pump down to vacuum levels below 1 × 10 ^-3 Pa. bottom. Different electrode designs for reduced graphene oxide were then made on the graphene oxide layer using a 1 × 10 ^-4 FIB fluence focused ion beam (FIB) direct writing technique. FIG. 29 shows electrode pair geometry made by this method, including (a) comb, (b) pad, (c) concentric, (d) zigzag, (e) L-shaped, and (f) maze. It outlines the shape of the school. Each pair of electrodes had the same distance between the electrodes and covered the same surface area on the silicon chip.

[0171] Electrochemical characterization was performed using a probe station with Biological's VSS potentiostat and Pt probe (5 μm diameter) in 1 M sodium sulphate to the reduced electrical contacts. Cyclic voltammetry (CV) was performed at different scan rates over the potential range of 0V-0.5V vs SHE. Electrochemical impedance spectroscopy (EIS) was performed by applying a sinusoidal perturbation of 10 mV at an open circuit potential over a frequency range of 10 MHz-1 MHz. CV and EIS measurements were also performed on the Pt probe in contact with the reduced GO to obtain control current, capacitance, and resistance values.

[0172] Table 1 shows the capacitance (calculated as mF / cm ² ) obtained at a low scanning speed of 1 mV / s for FIB-reduced graphene oxide electrodes with different geometries for comb-shaped electrode design. The one normalized to the obtained capacitance value is shown. It is clear from Table 1 that the geometry affects the capacitance value. The maze-shaped geometry shows the lowest capacitance, while the zigzag design shows the highest capacitance. The ESRs of all those electrodes were found to be equivalent, i.e. within the experimental error.

[0173]当業者には、ここに説明されている発明は具体的に説明されているもの以外の変更及び修正の余地があることが理解されるであろう。発明は本発明の精神及び範囲内に入る全てのその様な変更及び修正を含むものと理解される。

It will be appreciated by those skilled in the art that the inventions described herein have room for modification and modification other than those specifically described. The invention is understood to include all such modifications and modifications that fall within the spirit and scope of the invention.

Claims (25)

At least one porous film infiltrated with electrolyte,
A pair of separation electrodes arranged on a first surface of the porous film, wherein each electrode comprises a capacitive electrode material that ionically communicates with the porous film underneath the electrode. With multiple pairs,
Is equipped with
On the first surface of the porous film, a plurality of pairs of the separation electrodes are electrically connected and arranged in series and / or in parallel.
The electrolyte provides ion communication between the isolation electrodes through the internal pores of the porous film.
Capacitive energy storage device. The capacitive energy storage device of claim 1, wherein the pair of isolated electrodes has an inter-electrode separation distance of less than about 50 microns, preferably less than 30 microns. The capacitive energy storage device according to claim 1 or 2, wherein the pair of separation electrodes has a separation distance between electrodes smaller than the thickness of the porous film. The capacitive energy storage device according to any one of claims 1 to 3, wherein the pair of separating electrodes comprises a comb-shaped electrode having 2 to 6 fingers. The capacitive energy storage device of claim 4, wherein the fingers have a width of less than about 50 microns and a length of less than about 250 microns. The capacitive energy storage device according to any one of claims 1 to 5, wherein the electrode is electrically connected to an adjacent electrode and / or an external path without a metal current collector. The plurality of pairs of the separated electrodes are electrically connected by a conductive linkage on the first surface of the porous film, and the conductive linkage comprises a capacitive electrode material, according to claim 1 . The capacitive energy storage device according to any one of claims 6 . A plurality of porous films are stacked, and in the plurality of porous films, a plurality of pairs of the separation electrodes arranged on the first surface of the first porous film are the first. Any of claims 1 to 7 , which are stacked so as to be in contact with the back surface of the second porous film stacked on the porous film and preferably to allow ion communication. The capacitive energy storage device according to paragraph 1. At least one of the separation electrodes disposed on the first surface of the first porous film is on the first surface of the second porous film via a conductive path. The capacitive energy storage device according to claim 8 , which is electrically connected to at least one of the isolated electrodes arranged. The capacitive according to any one of claims 1 to 9 , wherein the at least one porous film is a flexible polymer film having a thickness of less than 100 microns, preferably less than 50 microns. Energy storage device. The capacitive energy storage device according to any one of claims 1 to 10 , wherein the capacitive electrode material comprises reduced graphene oxide. At least one porous film infiltrated with electrolyte,
One or more pairs of separated electrodes arranged on the first surface of the porous film, each electrode comprising a capacitive electrode material that ionically communicates with the porous film underneath the electrode. , A pair of separation electrodes,
Equipped with
The electrolyte provides ion communication between the isolation electrodes through the internal pores of the porous film.
The capacitive electrode material comprises reduced graphene oxide.
Capacitive energy storage device. The first porous film and
One or more pairs of separated electrodes arranged on the first surface of the first porous film, each electrode having a capacity for ion communication with the first porous film under the electrode. With a pair of isolation electrodes, which are equipped with a sex electrode material,
The first of the separation electrodes arranged on the first surface of the first porous film, which is a second porous film stacked on the first porous film. With the second porous film, one or more pairs are stacked so as to be in contact with the back surface of the second porous film.
With the electrolyte in the internal pores of the first and second porous films,
A stacked capacitive energy storage device. The stacked capacitive energy storage device according to claim 13, wherein the capacitive electrode material is ionically communicated with the back surface of the second porous film. The stacked capacitive energy storage device of claim 14, wherein the electrolyte provides ion communication between the isolation electrodes through the internal pores of the first and second porous films. One or more pairs of isolated electrodes disposed on the first surface of the second porous film, each electrode communicating ionically with a second porous film underneath the electrode . The stacked capacitive energy storage device according to any one of claims 13 to 15, further comprising a pair of separated electrodes, comprising a capacitive electrode material. At least one of the separation electrodes disposed on the first surface of the first porous film is on the first surface of the second porous film via a conductive path. The stacked capacitive energy storage device according to claim 16, which is electrically connected to at least one of the isolated electrodes arranged. A method of making capacitive energy storage devices ,
A step of applying a capacitive electrode material or pioneer material to the first surface of the porous film to form one or more pairs of isolated electrodes placed on the first surface.
The stage of infiltrating the porous film with an electrolyte and
Equipped with
The electrolyte provides ion communication between the isolation electrodes through the internal pores of the porous film.
Method. 18. The method of claim 18, wherein the capacitive electrode material or the ink comprising the precursor material is printed on the first surface. The method further comprises a step of providing the ink for printing on the first surface, the step of providing the ink of the capacitive electrode material or the precursor material in order to increase its viscosity. 19. The method of claim 19, comprising the step of concentrating the dispersion. The method according to any one of claims 18 to 20, wherein the separation electrode has a separation distance between electrodes of less than about 50 microns, preferably less than 30 microns. The step of applying the capacitive electrode material or the precursor material comprises a step of forming a plurality of pairs of the separated electrodes arranged on the first surface of the porous film, and the step of forming the separated electrodes. The method of any one of claims 18 to 21, wherein the plurality of pairs are connected in series and / or in parallel by a linkage comprising the capacitive electrode material or the precursor material. At the stage of stacking a plurality of porous films, the one or more pairs of the separation electrodes arranged on the first surface of the first porous film are the first porous. 22. The method described in any one of the items. At least one of the separation electrodes arranged on the first surface of the first porous film via a conductive path is placed on the first surface of the second porous film. 23. The method of claim 23, further comprising a step of electrically connecting to at least one of the isolated electrodes arranged. The capacitive electrode material or the precursor material comprises graphene oxide, the method of reducing the graphene oxide on the first surface of the porous film in order to produce reduced graphene oxide. The method according to any one of claims 18 to 24.

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