Ultracapacitor

Abstract

Disclosed is a capacitor having excellent performance. According to one aspect, provided is an ultracapacitor comprising: a positive electrode; a negative electrode; electrode tabs including at least one first electrode tab connected to the positive electrode and at least one second electrode tab connected to the negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte, wherein P in Equation 1 is 0.5 or more. [Equation 1] P= (L x N) / (T x F) In Equation 1, L is the winding length (mm) of the positive electrode or the negative electrode, N is half the total number of the electrode tabs included in the ultracapacitor, T is the thickness (µm) of the separator, and F is the capacitance (F) of the ultracapacitor.

Description

ultracapacitor

[0001] The present invention relates to capacitors, and more particularly to ultracapacitors.

[0002] Energy storage devices that store electrical energy include batteries and capacitors. Among these capacitors, ultracapacitors (UC), also known as supercapacitors (SC), possess characteristics intermediate between those of electrolytic capacitors and secondary batteries. Their high efficiency and long lifespan make them a viable next-generation energy storage device for use in conjunction with or as an alternative to secondary batteries.

[0003] Ultracapacitors are also used as a replacement for batteries in applications that require high maintenance requirements and a long service life. Ultracapacitors possess rapid charge and discharge characteristics, making them ideal for auxiliary power sources in mobile communication devices such as cell phones, laptops, and PDAs, as well as in high-capacity applications such as electric vehicles, nighttime road markings, and UPS (Uninterrupted Power Supply). Therefore, they are widely used in these applications.

[0004] Meanwhile, ultracapacitors currently in mass production typically use cellulose-based separators. However, cellulose-based separators are thicker than the polyolefin-based separators commonly used in other energy storage devices (e.g., lithium batteries). This can increase capacitor resistance. Furthermore, the increased thickness of the separator can lead to fewer electrodes being wound, which can lower energy density.

[0005] As the demand for ultracapacitors has diversified recently, the demand for capacitors with high energy density has increased, and many studies are being conducted to increase the energy density of ultracapacitors.

[0006] An object of the present invention is to provide a capacitor having improved energy density.

[0007] The purpose of the present invention is to provide a capacitor that has a high degree of freedom in terms of the configuration of components included in the capacitor when manufacturing the capacitor.

[0008] Another object of the present invention is to provide a capacitor with improved capacity retention.

[0009] The purposes of the present invention are not limited to those mentioned above, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof described in the specification.

[0010] According to one aspect of the present invention for achieving the above object, an ultracapacitor is provided, which comprises: a positive electrode; a negative electrode; an electrode tab including at least one first electrode tab connected to the positive electrode, and at least one second electrode tab connected to the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte; wherein P of the following equation 1 satisfies 0.5 or more.

[0011] [Formula 1]

[0012] P= (L x N) / (T x F)

[0013] In the above equation 1, L is the winding length (mm) of the positive or negative electrode, N is half of the total number of electrode tabs included in the ultracapacitor, T is the thickness (μm) of the separator, and F is the capacitance (F) of the ultracapacitor.

[0014] In one embodiment of the present invention, the winding length of the positive electrode and the winding length of the negative electrode may each independently be 570 to 1,750 mm.

[0015] In one embodiment of the present invention, the BET specific surface area of ​​the activated carbon included in the positive electrode is 1,500 to 2,500 m 2 / g, and the BET specific surface area of ​​the activated carbon included in the cathode is 1,500 to 2,500 m 2 / g may be.

[0016] In one embodiment of the present invention, N in the above formula 1 may be 2 or more.

[0017] In one embodiment of the present invention, the separation membrane may include a polyolefin resin.

[0018] In one embodiment of the present invention, the thickness of the separation membrane may be 5 to 20 μm.

[0019] In one embodiment of the present invention, the porosity of the separation membrane may be 40 to 70 vol%.

[0020] In one embodiment of the present invention, the capacitance of the ultracapacitor may be 50 to 1,200 F.

[0021] The solutions to the above problems are not exhaustive and may be combined with several embodiments of the present disclosure. The various features of the present invention and their corresponding advantages and effects can be understood in more detail by referring to the detailed description below.

[0022] According to one aspect of the present invention, a capacitor with improved energy density can be implemented.

[0023] According to one aspect of the present invention, a capacitor can be provided that has a high degree of freedom in relation to the configuration of components included in the capacitor.

[0024] In addition to the aforementioned effects, specific effects of the present invention are described below along with specific details for implementing the invention. Furthermore, the effects of the present invention are not limited to the effects described above and can be readily achieved using the means and combinations thereof described in the specification.

[0025] FIG. 1 is a drawing showing the configuration of an ultracapacitor according to one embodiment of the present invention.

[0026] FIG. 2 is a drawing showing an electrode tab included in an ultracapacitor according to one embodiment of the present invention.

[0027] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0028] The terms "comprise" and / or "comprising" in this specification specify the presence of stated features, steps, numbers, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements and / or groups thereof.

[0029] If multiple embodiments are described in this specification, the embodiments may be combined unless specifically stated otherwise. In this case, the effects of the present invention may be defined as including the effects derived from each embodiment and the effects resulting from the organic combination of the embodiments. For example, even if Embodiments 1 and 2 are described independently in this specification, Embodiments 1 and 2 may be organically combined with each other, unless the context clearly indicates otherwise, and the effects of the present invention may include the effects resulting from the combination of Embodiments 1 and 2.

[0030] The numerical range indicated by the term "to" in this specification refers to a numerical range that includes the values ​​described before and after the term as the lower limit and the upper limit, respectively. When multiple numerical values ​​are disclosed as the upper and lower limits of an arbitrary numerical range, the numerical range disclosed in this specification can be understood as any numerical range that has any one of the multiple lower limit values ​​and any one of the multiple upper limit values ​​as the lower limit and the upper limit, respectively. For example, when a to b, or c to d is described in the specification, it can be understood that a or more and b or less, a or more and d or less, c or more and d or less, or c or more and b or less is described.

[0031] In this specification, an "ultracapacitor" may be an electrical double layer capacitor (EDLC) having an operating principle in which ions contained in an electrolyte are adsorbed or desorbed on an electrode surface; a pseudocapacitor involving a surface chemical reaction; or a hybrid capacitor (hybrid supercapacitor) having the characteristics of these suitably mixed using an asymmetric electrode, and preferably an electrical double layer capacitor.

[0032] According to one aspect of the present invention, an ultracapacitor is provided, comprising: a positive electrode; a negative electrode; an electrode tab including at least one first electrode tab connected to the positive electrode, and at least one second electrode tab connected to the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte; wherein P of the following equation 1 satisfies 0.5 or more.

[0033] [Formula 1]

[0034] P= (L x N) / (T x F)

[0035] In the above equation 1, L is the winding length (mm) of the positive or negative electrode, N is half of the total number of electrode tabs included in the ultracapacitor, T is the thickness (μm) of the separator, and F is the capacitance (F) of the ultracapacitor.

[0036] According to one aspect of the present invention, by satisfying P of the above formula 1 as 0.5 or more, the effect of increasing the electrode winding length that can be wound on a capacitor while making the separator thinner can be realized, and the number of electrode tabs can be easily adjusted, thereby increasing the degree of freedom for the number of electrode tabs. According to another aspect of the present invention, by satisfying P of the above formula 1 as 0.5 or more, a capacitor with improved capacity retention can be realized.

[0037] Hereinafter, the configuration of the present invention will be described in more detail with reference to the drawings.

[0038] FIG. 1 is a drawing showing the configuration of an ultracapacitor according to one embodiment of the present invention.

[0039] Referring to FIG. 1, an ultracapacitor (100) according to the present invention includes a positive electrode (10), a negative electrode (30), a separator (20), and an electrolyte.

[0040] 1. Ultracapacitor

[0041] anode

[0042] The positive electrode (10) according to the present invention can store electric energy by having ions in the electrolyte move along the electric field and be adsorbed on the surface of the electrode.

[0043] The positive electrode (10) according to the present invention may include a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector. In some examples, the positive electrode active material layer may be disposed on one or both surfaces of the positive electrode current collector.

[0044] The positive electrode current collector according to the present invention can support the positive electrode active material layer to contribute to the structural stability of the positive electrode, and at the same time provide a path for the movement of charges released from or supplied to the positive electrode active material layer.

[0045] In some examples, the positive electrode current collector is not particularly limited and may be copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon; or may be surface-treated with carbon, nickel, silver, etc. on the surface of copper or stainless steel.

[0046] In some examples, the positive electrode current collector may include fine irregularities on its surface. Accordingly, the bonding strength of the positive electrode current collector to the positive electrode active material layer may be enhanced.

[0047] In some examples, the above-described positive electrode collector is not particularly limited and may be transformed into various forms such as a film, sheet, foil, mesh, net, porous structure, foam structure, or non-woven fabric.

[0048] The positive electrode active material layer according to the present invention may include a positive electrode active material, a conductive material, and a binder.

[0049] In some embodiments of the present invention, the positive electrode active material may include activated carbon. Specifically, the activated carbon is an aggregate of amorphous carbon with well-developed micropores manufactured from carbonaceous materials such as brown coal, anthracite coal, and bituminous coal. Through an activation process, micropores on the molecular scale are formed, resulting in a carbon material with a large internal surface area.

[0050] In some embodiments of the present invention, the BET specific surface area of ​​the activated carbon is 1,500 to 2,500 m 2 / g, 1,600 to 2,420 m 2 / g, preferably 1,900 to 2,420 m 2 / g, more preferably 1,600 to 2,000 m 2 / g may be. According to some embodiments of the present invention, by controlling the BET specific surface area of ​​the activated carbon within the above numerical range, the capacitance of the capacitor can be increased, and the charge / discharge speed of the capacitor can be increased.

[0051] In this specification, the average particle diameter of the particles is the particle diameter (D) when the cumulative percentage in the volume-based particle size distribution curve is 50% when measured by a laser diffraction particle size distribution measuring device. 50 ) can be defined. For example, the average particle diameter of the particles can be calculated by dispersing the target particles in a dispersion medium, introducing them into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam.

[0052] In some embodiments of the present invention, the average particle diameter (D) of the activated carbon 50 ) may be 5 to 20 μm, preferably 5 to 15 μm, and more preferably 5 to 10 μm.

[0053] In some embodiments of the present invention, the content of the activated carbon may be 65 to 95 wt%, preferably 80 to 92 wt%, and more preferably 90 to 92 wt%, based on the total weight of the positive electrode active material layer. Here, the total weight of the positive electrode active material layer may refer to the total solid content of the positive electrode slurry forming the positive electrode active material layer.

[0054] In some embodiments of the present invention, the pore size of the activated carbon may be 0.1 to 500 nm, 0.1 to 100 nm, preferably 1 to 100 nm, and more preferably 50 to 100 nm. For example, the pore size may be measured as a pore diameter analyzed in BJH when BET is specified.

[0055] In some embodiments of the present invention, the average size of the pores included in the activated carbon of the positive electrode may be 0.1 to 500 nm, preferably 1 to 100 nm, and more preferably 50 to 100 mm.

[0056] The conductive material according to the present invention can increase the electrical conductivity of the anode and reduce the resistance of the electrode.

[0057] In some examples, the above-described challenger may be, but is not limited to, specifically Super-P, Ketjen Black, acetylene black, carbon black, or graphite.

[0058] In some embodiments of the present invention, the content of the conductive material may be 3 to 20 wt%, preferably 5 to 10 wt%, based on the total weight of the positive electrode active material layer.

[0059] The binder according to the present invention can provide binding force between positive electrode active materials, between conductive materials, or between positive electrode active materials and conductive materials, and at the same time increase the adhesive force of the positive electrode active material layer to the positive electrode current collector.

[0060] In some embodiments of the present invention, the binder may include at least one selected from the group consisting of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), methyl cellulose (MC), styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), and polymethyl acrylate (Poly(methyl acrylate)), and specifically, carboxymethyl cellulose, polyvinylidene fluoride, and styrene-butadiene rubber.

[0061] In some embodiments of the present invention, the content of the binder may be 3 to 10 wt%, preferably 3 to 7 wt%, more preferably 4 to 6 wt%, and even more preferably 5 to 6 wt%, based on the total weight of the positive electrode active material layer.

[0062] As illustrated in FIG. 1, the capacitor (100) of the present invention may be wound in a circular shape with the positive electrode (10), the separator (30), and the negative electrode (20) laminated and wound, thereby ultimately having a cylindrical shape. In some examples, the part where the winding begins (approximately the central region of the wound capacitor (100)) may be defined as the winding tip, and the part where the winding ends (or ends) (approximately the outermost region of the wound capacitor (100)) may be defined as the winding end. At this time, the direction from the winding tip to the winding end of the circularly wound positive and negative electrodes may be defined as the longitudinal direction, and the length along which the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode are coated in the longitudinal direction may be defined as the winding length of the electrode.

[0063] Meanwhile, since the separator does not have an active material coating layer, the length wound around the capacitor from the winding tip to the winding end can be defined as the winding length of the separator.

[0064] In some embodiments of the present invention, the winding length of the positive electrode (10) in the longitudinal direction may be 570 to 1,750 mm. For example, the winding length of the positive electrode may be 570 mm or more, 600 mm or more, 620 mm or more, 700 mm or more, 800 mm or more, 900 mm or more, 1,000 mm or more, 1,100 mm or more, 1,200 mm or more, 1,300 mm or more, 1,400 mm or more, 1,500 mm or more, 1,600 mm or more, 1,650 mm or more, 1,700 mm or more, 1,710 mm or more, or 1,750 mm or more; 1,750 mm or less, 1,710 mm or less, 1,650 mm or less, 1,600 mm or less, 1,500 mm or less, 1,400 mm or less, 1,300 mm or less, 1,200 mm or less, 1,100 mm or less, 1,000 mm or less, 900 mm or less, 800 mm or less, 700 mm or less, or 620 mm or less; or any one or more of the plurality of lower limits may be less than or equal to any one of the plurality of upper limits.

[0065] The energy density can be increased by increasing the winding length of the anode inserted per unit capacitor, but the winding length of the anode that can be inserted into the capacitor is limited due to the space constraints of the capacitor.

[0066] In the present invention, by using a polyolefin separator instead of a relatively thick cellulose separator, a larger amount of positive electrodes can be wound within the capacitor to increase the energy density, and even without winding more positive electrodes to increase the energy density, room can be secured to include various elements within the capacitor, thereby increasing the degree of freedom in capacitor manufacturing.

[0067] cathode

[0068] The cathode (30) according to the present invention can store electric energy by having ions in the electrolyte move along the electric field and be adsorbed on the surface of the electrode.

[0069] The negative electrode (30) according to the present invention may include a negative electrode current collector and a negative electrode active material layer on at least one surface of the negative electrode current collector. In some examples, the negative electrode active material layer may be disposed on one or both surfaces of the negative electrode current collector.

[0070] The negative electrode current collector according to the present invention can support the negative electrode active material layer to contribute to the structural stability of the negative electrode, and at the same time provide a path for the movement of charges released from or supplied to the negative electrode active material layer.

[0071] In some examples, the negative current collector is not particularly limited and may be copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon; or may be surface-treated with carbon, nickel, silver, etc. on the surface of copper or stainless steel.

[0072] In some examples, the negative electrode current collector may include fine irregularities on its surface. Accordingly, the bonding strength of the negative electrode current collector to the negative electrode active material layer may be enhanced.

[0073] In some examples, the negative electrode current collector may be transformed into various forms such as a film, sheet, foil, mesh, net, porous structure, foam structure, or non-woven fabric.

[0074] The negative electrode active material layer according to the present invention may include a negative electrode active material, a conductive material, and a binder.

[0075] In some embodiments of the present invention, the negative active material may include activated carbon. Specifically, the activated carbon is an aggregate of amorphous carbon with well-developed micropores manufactured from carbonaceous materials such as brown coal, anthracite coal, and bituminous coal, and may be a carbon material having a large internal surface area due to the formation of micropores on the molecular scale through an activation process. According to some embodiments of the present invention, since the negative active material includes activated carbon, ions in the electrolyte can move along the electric field and be effectively adsorbed on the surface of the activated carbon.

[0076] In some embodiments of the present invention, the BET specific surface area of ​​the activated carbon is 1,500 to 2,500 m 2 / g, preferably 1,900 to 2,420 m 2 / g, more preferably 1,600 to 2,000 m 2 / g may be. According to some embodiments of the present invention, by controlling the BET specific surface area of ​​the activated carbon within the above numerical range, the resistance of the capacitor is lowered as the capacitance of the capacitor is increased, so that not only can the current pass better, but also the charge / discharge speed of the capacitor can be increased.

[0077] In some embodiments of the present invention, the average particle diameter (D) of the activated carbon 50 ) may be 5 to 20 μm, preferably 5 to 15 μm, and more preferably 5 to 10 μm. According to some embodiments of the present invention, by adjusting the average particle diameter of the activated carbon included in the negative electrode within the above numerical range, the capacitance of the capacitor is increased, thereby lowering the resistance of the capacitor and allowing better current passage, and also increasing the charge / discharge speed of the capacitor.

[0078] In some embodiments of the present invention, the content of the activated carbon may be 65 to 95 wt%, preferably 80 to 92 wt%, and more preferably 90 to 92 wt%, based on the total weight of the negative electrode active material layer. Here, the total weight of the negative electrode active material layer may mean the total solid content of the negative electrode slurry forming the negative electrode active material layer.

[0079] In some embodiments of the present invention, the pore size of the total pore volume of the activated carbon may be 0.1 to 500 nm, preferably 1 to 100 nm, and more preferably 50 to 100 nm. For example, the pore size may be measured as a pore diameter analyzed in BJH during BET specificity.

[0080] In some embodiments of the present invention, the average size of the pores contained in the activated carbon of the cathode may be 0.1 to 500 nm, preferably 1 to 100 nm, and more preferably 50 to 100 mm. The conductive material according to the present invention can increase the electrical conductivity of the cathode and lower the resistance of the electrode.

[0081] In some examples, the above-described challenger may be, but is not limited to, specifically Super-P, Ketjen Black, acetylene black, carbon black, or graphite.

[0082] In some embodiments of the present invention, the content of the conductive material may be 3 to 20 wt%, preferably 5 to 10 wt%, based on the total weight of the negative electrode active material layer.

[0083] The binder according to the present invention can provide bonding strength between negative electrode active materials, between conductive materials, or between negative electrode active materials and conductive materials, and at the same time increase the adhesive strength of the negative electrode active material layer to the negative electrode current collector.

[0084] In some embodiments of the present invention, the binder included in the negative electrode may include at least one selected from the group consisting of carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), methyl cellulose (MC), styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), and polymethyl acrylate (Poly(methyl acrylate)), and may include carboxymethyl cellulose, polyvinylidene fluoride, and styrene-butadiene rubber.

[0085] In some embodiments of the present invention, the content of the binder may be 3 to 10 wt%, preferably 3 to 7 wt%, more preferably 4 to 6 wt%, and even more preferably 5 to 6 wt%, based on the total weight of the negative electrode active material layer.

[0086] In some embodiments of the present invention, the winding length of the cathode (30) in the longitudinal direction may be 570 to 1,750 mm. For example, the winding length of the cathode may be 600 mm or more, 700 mm or more, 800 mm or more, 900 mm or more, 1,000 mm or more, 1,100 mm or more, 1,200 mm or more, 1,300 mm or more, 1,400 mm or more, 1,500 mm or more, 1,600 mm or more, 1,650 mm or more, or 1,700 mm or more; 1,750 mm or less, 1,700 mm or less, 1,650 mm or less, 1,500 mm or less, 1,400 mm or less, 1,300 mm or less, 1,200 mm or less, 1,100 mm or less, 1,000 mm or less, 900 mm or less, 800 mm or less, or 700 mm or less; or any one or more of the plurality of lower limits and any one or more of the plurality of upper limits.

[0087] The energy density can be increased by increasing the winding length of the cathode inserted per unit capacitor, but the winding length of the cathode that can be inserted into the capacitor is limited due to the space constraints of the capacitor.

[0088] In the present invention, by using a polyolefin separator instead of a relatively thick cellulose separator, a larger amount of negative electrodes can be wound within the capacitor to increase the energy density, and even without winding more negative electrodes to increase the energy density, room can be secured to include various elements within the capacitor, thereby increasing the degree of freedom in capacitor manufacturing.

[0089] Electrode tab

[0090] FIG. 2 is a drawing showing an electrode tab included in an ultracapacitor according to one embodiment of the present invention.

[0091] Referring to FIG. 2, an ultracapacitor (100) according to one embodiment of the present invention may include an electrode assembly (50) and an electrode tab (11) connected to the electrode assembly (50). Specifically, each electrode tab (11) may be connected to a lead (not shown).

[0092] The electrode assembly (50) according to the present invention may include an electrode including the positive and negative electrodes described above and a separator described later.

[0093] The electrode tab (11) according to the present invention can electrically connect the current collector within the electrode to an external circuit and at the same time uniformly distribute the current within the electrode.

[0094] An electrode tab (11) according to the present invention includes at least one first electrode tab (11a) connected to the positive electrode, and at least one second electrode tab (11b) connected to the negative electrode. Specifically, the first electrode tab (11a) can electrically connect a positive electrode collector included in the positive electrode with an external circuit, and the second electrode tab (11b) can electrically connect a negative electrode collector included in the negative electrode with an external circuit.

[0095] In some embodiments of the present invention, half of the total number of electrode tabs (11) included in the ultracapacitor (100) (N in the above equation 1, unit: pair) may be 2 or more, specifically 2 or more and 10 or less, and more specifically 2 or 3. For example, when N is 2, it means that 2 pairs of electrode tabs are provided in the capacitor, and in this case, the total number of electrode tabs may be 4. As another example, when N is 3, it means that 3 pairs of electrode tabs are provided in the capacitor, and in this case, the total number of electrode tabs may be 6. In this case, as the number of electrode tabs increases, the resistance of the ultracapacitor may decrease.

[0096] membrane

[0097] The separator (20) according to the present invention can facilitate the movement of ions in an electrolyte and electrically separate the positive and negative electrodes.

[0098] The separator (20) according to the present invention is interposed between the anode (10) and the cathode (30).

[0099] In some embodiments of the present invention, the separator may comprise a polyolefin resin. Specifically, the polyolefin resin may comprise any one selected from the group consisting of polyethylene, polypropylene, and mixtures thereof.

[0100] In some embodiments of the present invention, the weight average molecular weight (Mw) of the polyolefin may be 300,000 to 1,000,000 g / mol, or 400,000 to 800,000 g / mol, and preferably 600,000 to 700,000 g / mol. Meanwhile, ultracapacitors that are actually being mass-produced generally use cellulose-based separators. However, cellulose-based separators are thicker than polyolefin-based separators that are mainly used in other energy storage devices (e.g., lithium batteries), which may increase the resistance of the capacitor, and there is a problem that the energy density may decrease because the electrodes may be wound less by the thickness of the thickened separator.

[0101] As the demand for ultracapacitors has diversified recently, the demand for capacitors with high energy density has increased, and many studies are being conducted to increase the energy density of ultracapacitors.

[0102] Meanwhile, the ultracapacitor of the present invention is characterized by using a polyolefin-based separator rather than a conventionally used cellulose-based separator.

[0103] The inventors of the present invention have confirmed that when a polyolefin-based separator is used in a system that satisfies specific conditions instead of a cellulose-based separator with excellent mechanical strength, the energy density can be increased while maintaining the excellent characteristics of the capacitor, and even the degree of freedom in the configuration of capacitor components can be secured.

[0104] In particular, by using a polyolefin separator instead of a relatively thick cellulose separator, a larger amount of electrodes can be wound within the capacitor to increase the energy density, and even without further winding of electrodes to increase the energy density, room can be secured to include various elements within the capacitor, thereby increasing the degree of freedom in capacitor manufacturing.

[0105] In some embodiments of the present invention, the thickness of the separation membrane may be 5 to 20 μm, 9 to 16 μm, 9 to 12 μm, or 12 to 16 μm.

[0106] According to some embodiments of the present invention, the thickness of the separator is controlled within the above numerical range, thereby making the thickness thinner compared to existing cellulose-based separators, thereby increasing the energy density of the capacitor.

[0107] In some embodiments of the present invention, the porosity of the separation membrane may be 40 to 70 vol%, or 40 to 60 vol%, and specifically 42 to 49 vol%, based on the total pore volume of the separation membrane. According to some embodiments of the present invention, the porosity of the separation membrane

[0108] In some embodiments of the present invention, the Gurley permeability of the membrane may be 50 to 400 s / 100ml, 75 to 209 s / 100ml, or 200 to 300 s / 100ml.

[0109] electrolyte

[0110] The electrolyte according to the present invention can provide electrolyte ions (solutes) that are adsorbed or desorbed from a positive electrode active material or a negative electrode active material.

[0111] The electrolyte according to the present invention may include a solvent and a solute. At this time, when voltage is applied to each electrode, the cations and anions contained in the solute may be attracted to the electrode with the opposite charge, thereby forming a double layer of charge.

[0112] In some embodiments of the present invention, the solvent may include at least one selected from the group consisting of acetonitrile, propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, gamma-butyrolactone, sulfolane, dimethyl sulfoxide, and tetrahydrofuran.

[0113] In some embodiments of the present invention, the solute may include a quaternary ammonium salt. According to some embodiments of the present invention, by using a quaternary ammonium salt as the solute, the solubility of the solute in the electrolyte can be increased, thereby increasing the overall capacity of the capacitor, and the internal resistance of the capacitor can be lowered, thereby improving the energy efficiency of the capacitor.

[0114] In some examples, the cation of the solute may be any one selected from the group consisting of tetraethyl ammonium, triethylmethyl ammonium, trimethylethyl ammonium, ammonium having a 1,1-dialkyl heteromonocyclic compound, and ammonium-spirobicyclic compounds, and the anion of the solute may be hexafluorophosphate or tetrafluoroborate.

[0115] In some embodiments of the present invention, the concentration of the quaternary ammonium salt may be 0.5 to 2.0 M, preferably 0.7 to 1.4 M.

[0116] Meanwhile, unlike cellulose separators, polyolefin-based separators have low electrolyte wettability, and thus an additional pressure impregnation step can be performed after the electrolyte is injected. In some embodiments of the present invention, after the electrolyte is injected into the capacitor, the capacitor may be pressurized at a pressure of 0.1 to 10 bar, 0.1 to 8 bar, or 0.1 to 5 bar for a time period of 1 second to 3 hours, 2 seconds to 2 hours, 3 seconds to 1 hour, or 5 seconds to 30 minutes.

[0117] Properties of capacitors

[0118] Meanwhile, capacitance refers to the ability of a capacitor to store charge.

[0119] In some embodiments of the present invention, the capacitance of the ultracapacitor may be 50 to 1,200 F, 100 to 900 F, 100 to 720 F, 100 to 600 F, 100 to 350 F, or 350 to 600 F.

[0120] The ultracapacitor according to the present invention satisfies P of the following equation 1 as 0.5 or more.

[0121] [Formula 1]

[0122] P= (L x N) / (T x F)

[0123] In the above equation 1, L is the winding length (mm) of the positive or negative electrode, N is half of the total number of electrode tabs included in the ultracapacitor, T is the thickness (μm) of the separator, and F is the capacitance (F) of the ultracapacitor.

[0124] Specifically, by satisfying P of the above equation 1 as 0.5 or more, the effect of further increasing the winding length of the electrode while reducing the thickness of the separator can be realized, and the number of electrode tabs can be easily adjusted, thereby increasing the degree of freedom regarding the number of electrode tabs. In addition, by satisfying P of the above equation 1 within the above numerical range, the capacity retention ratio of the ultracapacitor can be further improved.

[0125] In some embodiments of the present invention, P of the above formula 1 may be 0.52 or more, 0.53 or more, 0.55 or more, 0.60 or more, 0.71 or more, 0.75 or more, 0.78 or more, 0.88 or more, 0.90 or more, or 0.92 or more, and specifically may be any one of the plurality of lower limits and 1.0 or less. According to some embodiments of the present invention, by adjusting P of the above formula 1 within the above numerical range, the capacity retention ratio of the ultracapacitor can be further improved.

[0126] In some embodiments of the present invention, the capacity retention rate of the ultracapacitor measured after leaving the ultracapacitor under a condition of applying a load to the cell for 192 hours under a constant voltage condition after constant current charging in an environment of 75°C may be 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, or 92% or more.

[0127] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0128] As used herein, terms such as "about" or "substantially" refer to a reasonable amount of variation from the term that does not significantly alter the final result. These terms may be interpreted to include a variation of at least ±5% or at least ±10%, provided that such variation does not alter the meaning of the term and render it invalid.

[0129] [Manufacturing Preparation Example: Preparation of Membrane]

[0130] Separators according to Comparative Preparation Examples 1 and 2 and Implementation Preparation Examples, each having the properties shown in Table 1 below, were prepared.

[0131] Porosity measurement method:

[0132] The porosity of a membrane refers to the ratio of the volume occupied by pores to the total volume of the membrane. Specifically, the porosity (vol %) of the membrane according to the above-mentioned preparation example was measured in accordance with ISO 1014: 2021.

[0133] Method for measuring permeability:

[0134] The Gurley permeability of the membrane was measured using a permeability measuring device (Toyoseiki Densometer). Here, the Gurley permeability is defined as the permeability of 1.0 in (100 ml) of air under a pressure of 567 g (1.21 kPa) in accordance with the Japanese Industry Standard (JIS). 2 (642 mm 2) is defined as the time required to pass through the membrane area. Specifically, the Gurley permeability of the polyolefin membrane according to the implementation preparation example was measured in accordance with ISO 5636-5:2013, and the Gurley permeability of the cellulose membrane according to the comparative preparation examples 1 and 2 was measured by taking three specimens of 100 mm x 200 mm and using the JIS C2300ㆍ2:2010 21.2 Gurley method (JIS P8117:2009).

[0135] Classification Comparison Preparation Example 1 Comparison Preparation Example 2 Implementation Preparation Example Material Cellulose Cellulose Polyolefin (M w =600,000 g / mol) Thickness (㎛) 253516 Density (g / cm) 3 )0.35~0.460.35~0.45-Basis weight (g / m) 2 )--7.85 g / m 2 Porosity (vol%)--47.65Gulley Permeability (s / 100ml)1~83~10104

[0136] [Manufacturing Example 1: Manufacturing of Ultracapacitor] Manufacturing steps of the positive electrode:

[0137] (i) BET surface area of ​​about 1,600 to 2,420 m 2 / g, and (ii) average particle size (D 50 ) was mixed with activated carbon powder having a particle size of about 8 μm; a conductive material (Super-P); and a mixed binder containing carboxymethyl cellulose (CMC) and SBR as binders at a weight ratio of 1:1 at a weight ratio of 90:5:5 (activated carbon:conductive material:mixed binder), and added to pure water (H2O) to prepare a cathode slurry having a total solid content of about 35 wt%.

[0138] The above positive electrode slurry was coated on both sides of aluminum foil (thickness: approximately 20 μm), and then dried to produce a preliminary positive electrode. The preliminary positive electrode was then thermo-compressed (pressed) to produce a positive electrode having a final thickness of approximately 200 μm to 300 μm.

[0139] Manufacturing steps of the cathode:

[0140] (i) BET surface area of ​​about 1,600 to 2,420 m 2 / g, and (ii) average particle size (D 50 ) was mixed with activated carbon powder having a particle size of about 8 μm; a conductive material (Super-P); and a mixed binder containing carboxymethyl cellulose (CMC) and SBR as binders at a weight ratio of 1:1 at a weight ratio of 90:5:5 (activated carbon:conductive material:mixed binder), and added to pure water (H2O) to prepare a cathode slurry having a total solid content of about 35 wt%.

[0141] The above cathode slurry was coated on both sides of aluminum foil (thickness: approximately 20 μm), and then dried to produce a preliminary cathode. The preliminary cathode was thermo-compressed (pressed) to produce a final cathode having a thickness of approximately 150 μm to 260 μm.

[0142] Manufacturing steps of electrode tabs:

[0143] Electrode tabs were welded and manufactured to be connected to both the positive electrode collector and the negative electrode collector. Specifically, the positive electrode collector can be divided into a first coated portion coated with the positive electrode slurry and a first uncoated portion not coated with the positive electrode slurry. Similarly, the negative electrode collector can be divided into a second coated portion coated with the negative electrode slurry and a second uncoated portion not coated with the negative electrode slurry. Here, in order to manufacture the electrode tab, a part of the first coated portion and a part of the second coated portion were scraped off to form new uncoated portions, respectively, and then the electrode tab was welded.

[0144] Manufacturing steps of the winding element:

[0145] The positive electrode with the electrode tab formed, the negative electrode with the electrode tab formed, and the separator of each of the above manufacturing preparation examples were wound using a winding machine to manufacture a winding element.

[0146] Preparation steps for electrolyte:

[0147] An electrolyte having a concentration of approximately 1.0 M was prepared by dissolving a salt containing tetraethyl ammonium and hexafluorophosphate in acetonitrile, a solvent.

[0148] Manufacturing steps of ultracapacitors:

[0149] After placing the above-mentioned winding element in an aluminum case, the above-mentioned electrolyte was poured into the aluminum case, and then the aluminum case was pressurized at a pressure of 0.1 to 5 bar for 10 seconds to 3 minutes, and then sealed to manufacture an ultracapacitor (cylindrical full cell).

[0150] [Experimental Example 1: Performance Evaluation of Ultracapacitors]

[0151] How to control the capacitance of a cell:

[0152] The capacitance of the cell was adjusted according to the size of the cell.

[0153] Method for controlling the thickness of the electrode active material layer:

[0154] Depending on the capacitance of the cell to be targeted, the thickness of the electrode active material layer was adjusted to the values ​​shown in Table 2 below.

[0155] Separation membrane electrostatic capacity (F)Separation membrane materialSeparation membrane thickness (T, ㎛)Number of electrode tabs (N)Anode winding length (L1, mm)Cathode winding length (L2, mm)Thickness of electrode active material layer (㎛)[Anode / Cathode]P1=(L1*N) / (T*F)P2=(L2*N) / (T*F)Comparative example 1Comparative preparation example 2100Cellulose352pair570545224 / 2000.330.31Example 1Example preparation examplePolyolefin162pair6206000.780.75Comparative example 2Comparative preparation example 2350Cellulose353pair1,5701,520228 / 2000.380.37Example 2Example preparation examplePolyolefin163pair1, 7101,6500.920.88Comparative Example 3Comparative Preparation Example 1600Cellulose 253Pair 1,6651,610230 / 1850.240.23Example 3Example Preparation Example Polyolefin 163Pair 1,7501,7000.550.53P1 and P2 are values ​​rounded to the third decimal place.

[0156] [Experimental Example 2: Capacity Retention Rate of Capacitors According to Parameters]

[0157] The capacitors of the above experimental example 1 were left for 192 hours under constant voltage conditions after constant current charging in an environment of 75°C, and then the residual capacity and resistance were measured.

[0158] Classification P1 (positive electrode) P2 (negative electrode) Capacity retention rate (%) Comparative example 10.330.3189.6 Example 10.780.7593.1 Comparative example 20.380.3787.9 Example 20.920.8891.5 Comparative example 30.240.2387.9 Example 30.550.5388.9

[0159] In Tables 2 and 3 above, since the new parameters (P1 or P2) derived from the winding length of the electrode, the number of electrode tabs, the thickness of the separator, and the capacitance of the cell satisfy 0.5 or more, the same capacity can be achieved even with a thinner separator. In addition, the energy density can be increased by winding more electrodes as needed, and thus, freedom can be secured in the configuration of components or capacity control in the manufacture of ultracapacitors, which is desirable.

[0160] In addition, it was confirmed that the effect of improving the capacity retention of the capacitor was realized if the new parameter (P1 or P2) derived using the winding length of the electrode, the number of tabs, the thickness of the separator, and the electrostatic capacity satisfied 0.5 or more. If the above parameter (P1 or P2) was less than 0.5, the problem of relatively low capacity retention was shown.

[0161] The features described in the above-described embodiment may be combined with other embodiments unless explicitly stated otherwise. Furthermore, while the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art utilizing the basic concepts of the present invention defined in the following claims also fall within the scope of the present invention.

[0162] [Explanation of symbols]

[0163] 100: Ultracapacitor

[0164] 10: Bipolar

[0165] 11: Electrode tab

[0166] 20: Membrane

[0167] 30: Cathode

[0168] 50: Electrode assembly

Claims

1. Bipolar; cathode; An electrode tab comprising at least one first electrode tab connected to the positive electrode, and at least one second electrode tab connected to the negative electrode; a separator interposed between the positive electrode and the negative electrode; and Containing an electrolyte; P in the following equation 1 satisfies 0.5 or more, Ultracapacitors: [Formula 1] P= (L x N) / (T x F) In the above equation 1, L is the winding length (mm) of the positive or negative electrode, N is half of the total number of electrode tabs included in the ultracapacitor, T is the thickness (㎛) of the above membrane, F is the capacitance (F) of the above ultracapacitor.

2. In paragraph 1, The winding length of the positive electrode and the winding length of the negative electrode are each independently 570 to 1,750 mm. Ultra capacitor.

3. In paragraph 1, In the above equation 1, N is 2 or more, Ultra capacitor.

4. In paragraph 1, The above separator comprises a polyolefin resin. Ultra capacitor.

5. In paragraph 1, The thickness of the above separation membrane is 5 to 20 ㎛, Ultra capacitor.

6. In paragraph 1, The capacitance of the above ultracapacitor is 50 to 1,200F. Ultra capacitor.

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