KR102203959B1 - Foldable electrode architectures, its manufacturing method and flexible device comprising the same - Google Patents

Abstract

The present invention relates to a foldable electrode structure, a method of manufacturing the same, and a flexible device including the same, and more particularly, to a microfiber-based substrate; And a functional material coated on the substrate. Including, the functional material, an active material; And at least one of a metal nanowire, a carbon nanowire, and a carbon nanotube; to a foldable electrode structure, a method of manufacturing the same, and a flexible device including the same.

Description

Foldable electrode structure, manufacturing method thereof, and flexible device including the same {FOLDABLE ELECTRODE ARCHITECTURES, ITS MANUFACTURING METHOD AND FLEXIBLE DEVICE COMPRISING THE SAME}

The present invention relates to a foldable electrode structure, a method for manufacturing the same, and a device including the same.

The commercialization of a'foldable phone' that folds a display has been made, and various foldable devices are being developed. Flexible-energy storage technology is an essential technology for the implementation of flexible electrical devices, including roll-up displays, implantable and wearable devices.

Flexible lithium-ion batteries (LIBs) for implementing flexible electric devices have technical limitations in dimensional stability due to external energy. For example, a typical double lithium-ion battery is a secondary battery in which lithium ions move between positive and negative electrodes and repeat charging and discharging, and these electrodes transfer electrons to the active material and the'active material' containing lithium ions. Haeju consists of a'current collector', a'conducting agent' and a'binder' that connects the two. This configuration is related to the following three mechanical properties in order to achieve the flexibility of the electrode: (1) cohesive force between active layer configurations including an active material, a conductive agent and a binder; (2) the adhesion between the active layer and the current collector and (3) the fracture toughness of the constituent materials. The active material, the conductive agent, and the binder are in powder form, so they are applied as a current collector on a foil made of aluminum or copper to form an electrode. However, since aluminum or copper, the current collector, is hard, the electrical conductivity decreases when bent or folded. There is this. Furthermore, there is a problem in that battery performance is deteriorated because the current collector and the active material are separated by repeated deformation.

The present invention is to provide a foldable electrode structure having excellent mechanical durability due to external energy as well as high energy density and capacity characteristics.

The present invention provides a method of manufacturing a foldable electrode structure according to the present invention, which can improve adhesion and loading density between an active material and a substrate.

The present invention is to provide a flexible device including a foldable electrode structure according to the present invention.

According to an embodiment of the present invention, a microfiber-based substrate; And a functional material coated on the substrate. Including, the functional material, an active material; And at least one of a metal nanowire, a carbon nanowire, and a carbon nanotube; it relates to a foldable electrode structure.

According to an embodiment of the present invention, the foldable electrode structure may have a loading density of 1 mg/cm ² or more of a functional material in the substrate.

According to an embodiment of the present invention, the functional material is wound or webbed with the microfibers to form a coating layer by a three-dimensional network network, and the active material is trapped in the three-dimensional network network. And, the functional material may be to form a coating layer with a thickness of 10% or more of the thickness of the substrate.

According to an embodiment of the present invention, the functional material may be impregnated with 10% or more of the thickness direction of the substrate.

According to an embodiment of the present invention, the functional material includes a metal nanowire and an active material, and the metal nanowire: a substrate: an active material may be included in a ratio of 1:1 to 5:1 to 10 (mass ratio). have.

According to an embodiment of the present invention, the functional material may include at least one of carbon nanowires, carbon fibers, and carbon nanotubes; And an active material, wherein at least one of the carbon nanowires, carbon fibers, and carbon nanotubes: base material: the active material may be included in a ratio of 1:1 to 5:1 to 10 (mass ratio).

According to an embodiment of the present invention, the functional material is one selected from the group consisting of graphite particles, expanded graphite particles, hard carbon particles, soft carbon particles, carbon fibers, graphene, carbon black, acetylene black, and ketjen black. It may further include the above carbon-based material.

According to an embodiment of the present invention, the metal nanowire may include at least one selected from the group consisting of transition metals, precious metals, rare earth metals, oxides thereof, and alloys thereof.

According to an embodiment of the present invention, the substrate is a woven fabric, a knitted fabric, or a non-woven fabric, and the substrate includes a pore size of 1 um to 20 um, a porosity of 20% to 60%, and a thickness of 10 um to 30 um. And, the substrate may have a liquid wettability of a contact angle of 50 degrees or less.

According to an embodiment of the present invention, the substrate includes microfibers having a diameter of 1 um to 100 um, and the microfibers include natural fibers, polymer fibers or both, and the polymer fibers are cellulose fibers. , Polyacrylic acid (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polyacrylonitrile (PAN), nylon, Polyethylene naphthalate (PEN), polyether sulfone (PES), polyether ether ketone (PEEK), polyphenyrene sulfide (PPS), polyvinylidene fluoride (PVDF) polysulfone (PSU), polyethylene terephthalate (PET) , Polyamide (PA), polycarbonate (PC), polyurethane (PU), and may include one or more selected from the group consisting of polystyrene (PS).

According to an embodiment of the present invention, the active material includes particles having a size of 50 nm to 500 nm, and the active material is (Li (Ni, Co, Al)O ₂ )-based active material (NCA), Li (Ni ，Mn, Co)O ₂ active material (NMC), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium titanium oxide, LTO ), lithium aluminum titanium phosphate-based active material (lithium aluminum titanium phosphates, LATP) and lithium aluminum germanium phosphate-based active material (lithium aluminum germanium phosphate, LAGP).It may include at least one selected from the group consisting of.

According to an embodiment of the present invention, it relates to a flexible device comprising an electrode formed to include a foldable electrode structure according to the present invention.

According to an embodiment of the present invention, a microfiber-based substrate for a negative electrode; And a metal nanowire for a negative electrode coated on the microfiber-based substrate for the negative electrode. And an anode active material for an anode; And a microfiber-based substrate for the positive electrode. A carbon-based material for the positive electrode of at least one of carbon nanowires, carbon fibers, and carbon nanotubes coated on the microfiber-based substrate for positive electrode; And it relates to a flexible device comprising an electrode including; a positive electrode structure including; and an active material for a positive electrode.

According to an embodiment of the present invention, the device may include at least one or more of display, mobile, energy conversion and energy storage functions.

According to an embodiment of the present invention, the device may be a lithium ion battery.

According to an embodiment of the present invention, preparing a microfiber-based substrate; And coating a functional material solution by ultrasonic spraying on the substrate. Including, and the functional material, an active material, a metal nanowire, a carbon nanowire, a carbon fiber and a carbon nanotube containing at least one of, to a method of manufacturing a foldable electrode structure.

According to an embodiment of the present invention, the step of coating by ultrasonic spraying may include ultrasonic spraying for a temperature of 50° C. or higher and 0.1 to 1 hour.

According to an embodiment of the present invention, the step of coating by spraying with ultrasonic waves includes 60 to 120 ultrasonic energy (kHz) and 1 to 10 speed (ml/min ^-1 ) ultrasonic spraying, and coating by ultrasonic spraying , It may be that the injection head moves while moving or swinging in the X and Y axis directions.

According to an embodiment of the present invention, further comprising the step of compressing the coated substrate,

The pressing may be performed at a temperature of 20° C. to 60° C. and a pressure of 1 bar to 10 bar.

According to an embodiment of the present invention, in the functional material solution, the metal nanowire to active material is included in a ratio of 1:1 to 1:20 (mass ratio), and in the functional material solution, carbon nanowires, carbon fibers, and carbon nanoparticles At least one of the tubes; The active material may be included in a ratio of 1:1 to 1:20 (mass ratio).

The present invention may provide a foldable electrode structure having excellent mechanical durability while having excellent flexible properties by forming a entangled or webbed microfiber-based electrode structure between the microfibers and the conductive nanowires.

The present invention can provide an electrode structure capable of easily adjusting the energy density per area by the number of folds of the electrode mat, that is, the number of layers stacked by folding.

The present invention can provide a flexible and foldable device, for example, a deformable lithium-ion battery, which can be deformed without deteriorating performance and structural destruction by repetitive folding and bending during operation.

The present invention can provide a high-performance flexible and foldable electrode structure without the application of a metal current collector or a binder, so that the weight of the electrode structure can be reduced and energy density per weight can be improved.

1 is, in accordance with an embodiment of the present invention, a) a manufacturing process by ultrasonic spraying of a foldable electrode structure, b) scanning electron microscopy (SEM) according to the injection time of the foldable electrode structure (LTO-loaded AgNW$MF). ), c) the image of the electrode structure after the twisting and folding of the foldable electrode structure (LTO-loaded AgNW$MF), d) the LTO-containing foldable electrode structure (LTO) measured by the 4-pole probe method. -loaded AgNW$MF), and e) conventional LTO-loaded Al (LTO|Al) and the weight of the LTO-containing foldable electrode structure (LTO-loaded AgNW$MF) according to the present invention. .
2 shows the change according to the deformation process of folding in the weight, microstructure and electrical properties of the foldable electrode structure (LTO-loaded AgNW$MF and CNT#MF electrode) according to the present invention, according to an embodiment of the present invention. As shown, a) change in the relative weight of the electrode after 1000 folding cycles, b) change in electrical resistance according to the folding cycle, and c) to j) SEM images, more specifically, c) the measurement position of the SEM image, df ) Top view of LTO-loaded AgNW$MF: d) Before folding (LTO loading = 5 mg _LTO cm ^-2 ), e) After 500 folding cycles, and f) After 1000 folding cycles, gj) LTO-loaded CNT Top view of #MF: g) before folding (5 mg _LTO cm ^-2 ), h) after 250 folding cycles (5 mg _LTO cm ^-2 ), i) after 600 folding (1 mg _LTO cm ^-2 ) and j) Images after 1000 folding cycles (0.5 mg _LTO cm ^-2 ).
3 is, according to an embodiment of the present invention, a foldable electrode structure according to the present invention (LTO-loaded AgNW$MF and CNT#MF electrode) and inversion including a conventional LTO-loaded Al (LTO|Al), respectively It shows the lithiation electrochemical characteristics of a) a) capacity retention characteristics by repetition of charging and discharging at 1 C, and b) rate capabilities, c) Differential capacities at 1 C (dQ/dV )) curve, d) capacity ratio of folded AgNW$MFs (2L and 4L) versus unfolded AgNW$MFs (1L) according to repetition of charging and discharging at 1 C, and e) capacity ratio of folded AgNW$MFs, f ) It shows the capacity retention characteristics of a half-cell folded at different angles at 1 C.
4 is a bent highly flexible battery (AgNW$MF|LTO||) including a foldable electrode structure (LTO-loaded AgNW$MF and LFP-loaded CNT#MF) according to an embodiment of the present invention. LFP|CNT#MF)'s electrical properties, a) structure of highly flexible battery, b) open circuit voltage of LTO||LFP battery before and after bending, c) NW@MF- under folding, bending and hammering based on Red LEDs driven by LTO||LFP, d) voltage profile of 1L (unfolded)- and 4L (2 semi-folded)-based LTO||LFP at 1 C, e) capacity retention at 1 C and f ) It shows a comparison between the flexible battery reported in terms of area capacity and bending radii and the 4L-NW@MF-based battery according to the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms used in the present specification are terms used to properly express a preferred embodiment of the present invention, which may vary depending on the intention of users or operators, or customs in the field to which the present invention belongs. Accordingly, definitions of these terms should be made based on the contents throughout the present specification. The same reference numerals in each drawing indicate the same members.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

The present invention relates to a foldable electrode structure, and according to an embodiment of the present invention, the foldable electrode structure includes: a microfiber-based substrate; And functional substances; Including, the functional material, an active material; And a nanostructure.

According to an embodiment of the present invention, the foldable electrode structure is capable of loading and bonding of an active material on the surface and inside of the substrate without a current collector such as metal and a binder, and is bent, folded, or wrinkled during charging and discharging. It is possible to provide an electrode assembly in which operation is possible without a change in resistance even when a modification process such as, etc. is performed, and in which stable capacity is secured and capacity size is easily adjusted. In addition, the foldable electrode structure includes a positive electrode structure and a negative electrode structure, and the positive electrode structure and the negative electrode structure may be assembled into a basic configuration of an electrode without a current collector.

The microfiber-based substrate is a substrate coated with the active material and the nanostructure and impregnated into at least a portion of them, and realizes lighter weight of the electrode structure, and can provide flexibility and foldable function.

The microfiber-based substrate may be a porous substrate having entanglement between microfibers and voids due to a plurality of layers by microfibers. The microfiber-based substrate is a woven fabric, a knitted fabric, or a nonwoven fabric, and the substrate includes a pore volume of 1 to 10 (cm ³ /g), 20% to 60%; Or 30% to 60% porosity (the ratio of the void autonomous volume in the total volume of the substrate) and 1 um to 20 um; Alternatively, it may include macropores having a size of 1 um to 10 um. If the pore volume, porosity, and pore size are within the range, the active material and the nanomaterial are well impregnated and coated in the substrate, and the loading amount and adhesion of the active material can be improved by forming a three-dimensional network between the nanomaterial and the substrate. have. In addition, it is possible to provide a highly flexible and deformable electrode structure without degradation of performance after deformation by external force such as bending or bending.

The substrate includes a thickness of 10 um to 30 um, and if it is included within the thickness range, the foldable property of the electrode structure is prevented from decreasing due to a decrease in flexibility due to an excessive thickness, and energy density per weight by weight increase Can be prevented.

The microfiber-based substrate is 50 degrees or less; 30 degrees or less; It has a wettability by a wetting angle of 10 degrees or less, and for example, this may be a surface of at least one surface on which the coating process is performed on the substrate, or a characteristic over the entire substrate. Due to this wettability, the droplets sprayed on the substrate have increased affinity with the microfibers, so that absorption, dispersion, and impregnation are well performed on the surface or/and the entire surface of the substrate, thereby reducing the loading amount and adhesion of the functional material. Can be improved. The microfiber-based substrate has lipophilicity, hydrophilicity, or both, and preferably may be hydrophilic.

The microfiber-based substrate includes microfibers having a diameter of 1 um to 100 um, and when the diameter range is applied, micro-sized pores are well formed, and three-dimensional between nanostructures of a functional material Network can be formed well.

The microfibers include natural fibers, polymer fibers or both, and the polymer fibers include cellulose fibers, polyacrylic acid (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate ( PET), polypropylene terephthalate (PPT), polyacrylonitrile (PAN), nylon, polyethylene naphthalate (PEN), polyethersulfone (PES), polyetheretherketone (PEEK), polyphenyrene sulfide (PPS), polyvinylidene fluoride (PVDF), polysulfoam (PSU), polyethylene terephthalate (poly(ehtyleneterephthalate), PET), polyamide (PA), polycarbonate (PC), polyurethane ( PU), polystyrene (PS), polyacrylonitrile, poly(benzimidazol) (poly(benzimidazol), PBI), polyetherimide (PEI), poly(ethylene oxide) )), polyethylene (PE), poly(styrene-butadiene-styrene) triblock copolymer (poly(styrene-butadiene-styrene) triblock copolymer), polysulfone, poly(triethylene terephthalate) (poly (triethyleneterephthalate)), polyurethane (polyurethane), polyurethane urea (poly(urethane urea)), poly(vinyl alcohol) (poly(vinyl alcohol)), poly(vinyl carbazol)), poly (Vinyl chloride) (poly(vinyl chloride)), poly(vinyl pyrrolidone) (poly(vinyl pyrrolidone)), poly(vinylidene fluoride) (poly(vinylidene fluoride), PVDF) and poly(vinylidene fluoride) -Co-hexafluoropropylene) (poly(vinylidene fluoride-) It may contain at least one selected from the group consisting of co-hexafluoropropylene) and P(VDF-HFP)).

The active material may be applied without limitation as long as it is an active material applied in the technical field of the present invention, and may be, for example, a positive electrode and a negative electrode active material applied to a lithium ion battery. More specifically, the active material is lithium iron phosphate (LFP), lithium manganese complex oxide, lithium cobalt oxide (LCO), lithium nickel oxide, vanadium oxide, or one or more transition metals substituted (Li (Ni, Co, Al)O ₂ )-based active material (NCA), Li (Ni, Mn, Co) O ₂ may be a positive electrode active material such as an active material (NMC), but is not limited thereto. Lithium cobalt oxides such as LiCoO ₂ ; Lithium nickel oxides such as LiNiO ₂ ; Lithium manganese oxides such as formula Li _1+x Mn _2-x O ₄ (wherein x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site-type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _2-x MxO ₂ (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (where M = Fe, Co, Ni, Cu or Zn) may be a lithium manganese composite oxide, etc., and LiMn ₂ O _{4 in} which part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like may be used together, but are not limited thereto.

The active material is a lithium titanium oxide-based active material (lithium titanium oxide, LTO),

Lithium aluminum titanium phosphates (LATP), lithium aluminum germanium phosphates (LAGP) or Mg, Nb, Cu, Mn, Ni, Fe, Ru, Zr, B, It may be a compound in which at least one transition metal among Ca, Co, Cr, V, Sc, Y, La, Zn, Al, and Ga is substituted. The lithium titanium oxide (LTO) is represented by the formula LixTiyO ₄ (0.5≤x≤3; 1≤y≤4), for example, Li _0.8 Ti _2.2 O ₄ , Li _2.67 Ti _1.33 O ₄ , Li _1.33 Ti _1.67 O ₄ , Li _1.14 Ti _1.71 O ₄ , Li ₄ Ti ₅ O ₁₂ , Li ₂ TiO ₃ , Li ₂ Ti ₃ O ₇ , and the like. Additionally, the negative active material is Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe , Pb, Ge; Me': Al, B, P, Si, elements of groups 1, 2, and 3 of the periodic table, halogen; 0<x≤1;1≤y≤3; 1≤z≤8), etc. Metal complex oxide; Lithium metal; Lithium alloy; Silicon-based alloys; Tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide or the like may be further used.

The active material may be powder, needle, wire, tube, fiber, rod, sphere, polygon, or the like. Preferably, in order to increase adhesion to the substrate by the three-dimensional network of nanomaterials, it may be in the form of a powder. The active material may have a size smaller than the diameter, length, etc. of the nanomaterial, preferably 50 nm or more; 500 nm or more; Nano size from 50 nm to 500 nm; Alternatively, it may be a particle of 50 nm to 50 μm. The size may be a diameter, a length, a thickness, etc., depending on the shape of the active material. When included within the above size range, a uniform mixture with the nanomaterial is formed, the trap is well formed in the three-dimensional network of the nanomaterial formed during the coating process, and the adhesion of the active material in the electrode structure, loading density, etc. I can.

The nanostructures are entangled or webd with the microfibers during the coating process to form a three-dimensional network between the nanostructures, and trap functional materials such as active materials in the three-dimensional network to prevent adhesion of functional materials such as active materials to the substrate. Can be improved. A portion of the nanostructure may be impregnated in the cabin, and a coating layer may be formed on the substrate with a predetermined thickness.

The nanostructure is a nanomaterial having the form of a nanowire, a nanotube, a nanofiber, or the like, and may include, for example, at least one of a metal nanowire, a carbon nanowire, and a carbon nanotube.

The nanostructure, 1 nm or more; 50 nm or more; It may have a size of 50 nm to 500 μm, and the size may mean diameter, thickness, length, and the like. If it is within the above size range, the formation of a 3D network between nanostructures is well performed, uniform mixing between the active material and the nanostructures in the coating solution is achieved, and the loading density of the active material, adhesion, etc. using this 3D network network Can improve.

The metal nanowire may include at least one selected from the group consisting of transition metals, precious metals, rare earth metals, oxides thereof, and alloys thereof. For example, the oxides are titanium oxide (TiO ₂ ), cerium oxide (CeO ₂ ), zirconium oxide (ZrO ₂ ), magnesium oxide (MgO), copper oxide (CuO), tungsten oxide (WO ₃ ), nickel oxide (NiOx), cobalt oxide (CoOx), manganese oxide (MnOx), vanadium oxide (VOx), iron oxide (FeOx), gallium oxide (GaOx), cesium oxide (SeOx), molybdenum oxide (MoOx), etc., and the transition Metals are scandium (Sc), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zirconium (Zr), niobium (Nb), molybdenum ( Mo), technetium (Tc), lead (Pb), bismuth (Bi), germanium (Ge), zinc (Zn), etc., and the noble metal is silver (Ag), gold (Au), platinum (Pt), It may be ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and the like, and the rare earth metal is lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium ( Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium ( Yb), lutetium (Lu), scandium (Sc), yttrium (Y), and the like.

According to an embodiment of the present invention, when the functional material includes a metal nanowire and an active material, the metal nanowire: the substrate: the active material is 1:1 to 5:1 to 10 (mass ratio); Or 1:1.2 to 2:1.5 to 5 (mass ratio) may be included. Alternatively, the functional material may include at least one of carbon nanowires, carbon fibers, and carbon nanotubes; And an active material; in the case of including, at least one of the carbon nanowires, carbon fibers, and carbon nanotubes: the base material: the active material is 1:1 to 5:1 to 10 (mass ratio); Or 1:1.2 to 2:1.5 to 5 (mass ratio) may be included. When included within the mass ratio range of the functional material, the loading amount and adhesion of the active material in/on the substrate are improved by a three-dimensional network such as metal nanowires and carbon nanowires, and external forces such as repetitive bending and bending It is possible to provide a foldable electrode structure having excellent mechanical durability without deterioration in performance even in the deformation caused by.

According to an embodiment of the present invention, the functional material is one selected from the group consisting of graphite particles, expanded graphite particles, hard carbon particles, soft carbon particles, carbon fibers, graphene, carbon black, acetylene black, and ketjen black. It may further include the above carbon-based material.

According to an embodiment of the present invention, the functional material is wound or webbed with the microfibers to form a coating layer by a three-dimensional network network, and the functional material is 10% or more of the thickness of the substrate. ; More than 30%; A coating layer can be formed with a thickness of 80% or more. By forming the coating layer having the above thickness, it is possible to increase the loading density of the active material and improve energy density per area, conductivity, and the like. For example, the coating layer of the functional material is 1 nm or more; 100 nm or more; More than 1 micrometer; Or 100 micrometers or more.

According to an embodiment of the present invention, the functional material, 10% or more of the thickness direction of the substrate; More than 30%; Alternatively, it is impregnated in an amount of 50% or more, and impregnation of such a functional material may prevent deterioration of the electrode performance after repeated bending or folding due to external force, and improve durability.

According to an embodiment of the present invention, the foldable electrode structure is 1 mg/cm ² or more; 2 mg/cm ² or more; 5 mg/cm ² or more; Alternatively, it may have a loading density of 10 mg/cm ² or more of a functional material, for example, the loading density may be related to the active material.

According to an embodiment of the present invention, the foldable electrode structure may have a charging capacity per unit area of 0.75 mAh cm ^-2 or more, 1.5 mAh cm ^-2 or more, or 3.0 mAh cm ^{-2 or} more.

According to an exemplary embodiment of the present invention, the foldable electrode structure may have a flat plate shape or may be bent in a wave shape at a certain period.

According to an embodiment of the present invention, it relates to a flexible device including a foldable electrode structure according to the present invention.

The flexible device may include an electrode made of the foldable electrode structure, an electrode assembly, and/or a battery.

The flexible device may include at least one of a display, a mobile device, an energy conversion function and an energy storage function, and the device may be a solar cell or a lithium ion battery.

For example, microfiber-based substrates for negative electrodes; And a metal nanowire for a negative electrode coated on the microfiber-based substrate for the negative electrode. And an anode active material for an anode; And a microfiber-based substrate for the positive electrode. A carbon-based material for the positive electrode of at least one of carbon nanowires, carbon fibers, and carbon nanotubes coated on the microfiber-based substrate for positive electrode; And a positive electrode structure including a; and an active material for a positive electrode, an electrode assembly, or a flexible device including a battery. In addition, the anode structure and the cathode structure may be in direct contact or may further include a separator between them.

The separator may include polyolefins such as the aforementioned microfiber-based substrate, polyethylene, polypropylene, polymethylpentene, and blends; Polyimidazole, polybenzimidazole (PBI), polyimides, polyamideimides, polyaramids, polysulfones, aromatic polyesters ) And polyketones (polyketones) may be a porous member lane containing a polymer. When the microfiber-based substrate is applied to the separator, the substrate may be the same as or different from the substrate applied to the electrode structure.

The electrode assembly and the battery may further include a configuration applied in the technical field of the present invention, provided it does not depart from the object of the present invention. For example, it may be an electrolyte or the like, but it is not specifically mentioned in the present specification.

The present invention relates to a method of manufacturing a foldable electrode structure, and according to an embodiment of the present invention, the manufacturing method improves the loading density and adhesion of a functional material, for example, an active material, and repetitive wrinkles, Even after folding, it is possible to provide a flexible foldable electrode structure having excellent mechanical durability and capacity retention without deteriorating performance and structural destruction.

According to an embodiment of the present invention, preparing a microfiber-based substrate; And ultrasonically spraying a functional material solution onto the substrate to coat it.

The step of preparing the microfiber-based substrate is a step of preparing the microfiber-based substrate, and if necessary, an organic solvent such as an alcohol having 1 to 4 carbon atoms to increase the wettability of the microfiber-based substrate And it may be pre-treated by a method such as coating or immersion with water, etc., the pre-treatment may be carried out at room temperature to 100 ℃. If necessary, a drying process may be further included after the pretreatment.

The step of ultrasonically spraying the functional material solution onto the substrate to coat it may include preparing a functional material solution and ultrasonically spraying the functional material solution.

In the preparing of the functional material solution, the functional material is dispersed by mixing the above-mentioned functional material and a solvent, and a functional material solution for ultrasonic spraying is prepared. The functional material is as mentioned above.

The solvent may include water, an organic solvent, or both. The organic solvent may be an alcohol solvent including methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and an ether solvent including diethyl ether, dipropyl ether, dibutyl ether, butyl ethyl ether, and tetrahydrofuran. .

The functional material solution includes a metal nanowire and an active material, and in the functional material solution, the metal nanowire to the active material is 1:1 to 1:20 (mass ratio); Or 1:1 to 1:10 (mass ratio); The functional material solution includes at least one of carbon nanowires, carbon fibers, and carbon nanotubes and an active material, and includes at least one of carbon nanowires, carbon fibers and carbon nanotubes in the functional material solution; The active material is 1:1 to 1:20 (mass ratio); Or 1:1 to 1:10 (mass ratio); If included within the mass ratio range, uniform mixing between functional materials is achieved, and in particular, the direct rate of the active material is maintained while maintaining excellent adhesion of the active material by a three-dimensional network network of metal nanowires, carbon nanowires, carbon fibers and carbon nanotubes. By increasing the capacity, an electrode structure with improved capacity can be provided.

It may contain 0.1 to 10 parts by weight of a functional material based on 100 parts by weight of the functional material solution.

The ultrasonic spraying is a step of supplying the functional material solution to the spray head (nozzle) on the substrate and ultrasonically spraying it to coat. For example, 30° C. or higher; 50 ℃ or higher; Alternatively, it is carried out at a temperature of 50° C. to 100° C., and if it is included within the above temperature range, sufficient volatilization of a solvent and impregnation and coating of the functional material may be performed smoothly.

The ultrasonic injection may be performed for 1 second or longer; 0.1 to 1 hour; 1 second to 10 minutes; Alternatively, it may be ultrasonic injection for 1 second to 10 seconds.

The ultrasonic spraying may include 50 kHz or more; Alternatively 50 kHz to 300 kHz; Ultrasonic energy of and more than 200 W; Or applying an ultrasonic power of 200 W to 400 W, and 0.1 (ml/min ^-1 ) or more; 0.2 (ml/min ^-1 ) or more; 5 (ml/min ^-1 ) or more; Alternatively, ultrasonic injection may be performed at a rate of 1 (ml/min ^-1 ) or more.

In the step of ultrasonic spraying, the spraying head may be moved while moving or swinging in a height or X and Y axis directions to evenly spray the functional material solution over the entire substrate, and coating a large area substrate may be possible. .

According to an embodiment of the present invention, the step of coating by ultrasonic spraying further comprises compressing the coated substrate, and the compressing step is performed by compressing at a temperature of 20° C. to 60° C. and a pressure of 1 bar to 10 bar. It is possible to increase adhesion and impregnation of functional materials.

According to an embodiment of the present invention, a drying step may be further included, and the drying step may be performed after each step or after the final step. The drying may be performed at room temperature to 200°C; Alternatively, it may be 50 ℃ to 100 ℃.

Example

Fabrication of electrode structure

As shown in FIG. 1, Non-woven PET MF mats (Amotech) were coated with a mixed aqueous solution of nanowires and active materials using an ultrasonic spray (Sono-Tek) having a 120 kHz nozzle. One of the coating solutions of nanowires and active materials was sprayed at a flow rate of 0.2 ml min ^-1 by placing PET MF mats on a 150°C heater. The spray nozzle moved 0.2 cm s ^-1 on the xy axis and coated with a large area electrode. The spraying process was repeated until the desired accumulation amount was obtained. AgNW (Nanopyxis) or CNT (single wall; Meijo Nano Carbon) is used as a nanowire, and LTO (Lithium titanate, Li ₄ Ti ₅ O ₁₂ ; Ishihara Sangyo Kaisha) and LFP (lithium iron phosphate, LiFePO ₄ ; SudChemie) are respectively It was applied as an active material for anode and cathode. A rubber cylindrical roller (diameter = 30 mm) was pressed by rolling the prepared electrode several times.

The aqueous coating solution was prepared by ultrasonic-sonic treatment of an aqueous dispersion mixture of nanowires and active material in a solid content of 2:8 for 30 min. 30 mg mL ^-1 AgNW (aq) or 1 mg mL ^-1 CNT (aq) is used for aqueous nanowire dispersions, while 30 mg mL ^-1 LTO (aq) or 30 mg mL ^-1 LFP (aq) is It was used in water-soluble active material dispersion. 10 mg mL ^-1 sodium dodecylbenzenesulfonate (SDBS, Sigma Aldrich) was used as a dispersant for CNTs in water. CNT-containing electrodes were washed several times with distilled water and ethanol and the surfactant was removed. Hereinafter, AgNW and CNT-coated PET MF mat electrodes are denoted by AgNW$MF and CNT#MF, respectively.

Manufacturing of cells

Half cells were tested with 2032 coin-type cells, and the entire cells were assembled in the form of 5 cm x 3 cm pouch-type cells. All cells were assembled in an Ar-filled glove box, and a porous polyethylene membrane (Asahi NH 716) was assembled in the form of a sandwich between two electrodes. LTO-loaded CNT#MF or LTO-loaded AgNW$MF was assembled with lithium metal in a coin-type battery. The LFP-loaded CNT#MF cathode and LTO-loaded AgNW$MF anode were assembled in a flexible pouch. The aluminum and nickel lead tabs were attached in the cathode and anode with polyimide tape, respectively. 1 M LiPF ₆ in ethylene carbonate/diethyl carbonate (EC:DEC in 3:7 by weight; Panax Etec) was used as the electrolyte.

Property evaluation

The electrical conductivity and sheet resistance of the flat electrode were measured by a four-point probe method (Dasol FPP-RS8). The resistance of the electrode upon folding and unfolding was measured by a multimeter, and repetitive folding and unfolding was performed with a tensile strength machine (Petrol LAB DA-01). The sample electrode was electrically connected to the gold-coated jig by silver paste and fixed in the equipment.

Coin-type and pouch-type half-cell and pouch-type whole cells were galvanostatically lithified and delithiated by a cycle test (WonATech WBCS 300), and the lithiation and delithiated capacity were measured. In electrochemical measurements, pouch-shaped cells were made by folding at the desired angle by a tensile strength device.

result

1 is, according to an embodiment of the present invention, LTO-loaded AgNW$MF (AgNW: MF: LTO = 1:1.1:5 (w/) having a loading density of LTO = 5 mg _LTO cm ^-2 w) of a) manufacturing process, b) SEM (Scanning electron microscopy) images at three different injection times, c) images of electrodes after twisting and folding, d) LTO-loaded electrode structures measured by the 4-pole probe method The electrical conductivity of was shown, and the thickness of the electrode structure was measured by "vernier caliper". The active layer of LTO|Al is composed of carbon black: binder: LTO = 0.5:0.5:5 (weight), and CNT#MF containing LTO is composed of CNT:MF:LTO=1:1.1:5 (weight) do. In LTO|Al, LTO = 4.3 mgLTO cm ^-2 , and in CNT#MF, LTO = 5 mg LTO cm ^-2 . e) Current-current-collector-free and binder-free AgNW$MF is used to reduce weight, compared to conventional LTO-loaded Al (LTO|Al), m/m0 = relative electrode weight, and electrode weight is It is the sum of the weights of all components of the electrode structure including the conductive material, the binder and the active material, as well as the current collector of AgNWs, AgNW$M PET MF and LTO|Al. 2L (L = layer) and 4L AgNW$MF were obtained by folding half and two unfolded AgNW$MF (1L), respectively. The size is indicated in centimeters at the top.

As shown in (a) of FIG. 1, an NW@MF electrode structure was manufactured using an ultrasonic spray method, and the active material and the conductive material NWs (nanowires, 8:2, w/w) were uniformly mixed in water. The resulting powder is introduced into the nozzle, and ultrasonic waves are applied in the nozzle at 120 kHz to spray onto a PET nonwoven mat. PET nonwoven mats have micrometer-scale macrovoids and submicron gaps between the layers. It has excellent wettability to water (<5°) on the macroporous PET mat, which causes water-soluble droplets of the dispersion to pass through pores and inner layers of MFs (fibers in micrometer) to contact the entire surface of MFs. The solvent is immediately dried at a temperature of 150° C., and NWs and lithium titanate (LTO) particles are loaded on the surface of both the front surface and the inner layer of the MFs. The excellent wettability of the dispersion sprayed on the substrate in the NW@MF structure may be a factor in which the physical interaction between NWs and MFs determines the adhesion between the active material and layers on the substrate. In other words, the macroporosity and not-too-hydrophobic surface properties of the PET nonwoven mat provide excellent wettability. On the other hand, in the case of PE (nanoporous polyethylene, pore size = tens of nanometers, hydrophobicity, contact angle = 114 °), NWs are not injected into the substrate, and the adhesion to the substrate is weak.

In the case of the initial spraying time (1 s) in FIG. 1B, the MFs of the PET mat are AgNWs (diameters = about 20 nm, lengths = about 20 μm). When NWs are injected onto the MFs, they collide with the MFs, and the collision force forms a form of ductile AgNWs according to the surface characteristics of the MFs, and a part of the collision force is caused by ductile deformation. Used. Also, the reduced impact force causes AgNWs to wind up MFs,

The ductility of Ag makes it possible to form interlocking bonds between AgNWs. As the injection time increases, more AgNWs and active material particles are present along the curved surface of the MFs. After 10 s injection, the AgNWs form an interconnected network, and the LTO particles are trapped between the AgNWs and MFs. The pores between the MFs in the PET mat are filled with LTO particles trapped by the AgNW web. In addition, in the case of CNTs (diameter = about 10 nm, length = about 25 μm), MFs are webbed with CNTs on the surface. That is, the CNT-CNT interaction is stronger than that of CNT-PET, and the formation of interlocking joints is not found between CNTs due to CNTs inductile properties.

In the spraying process, the spraying nozzle moves in the xy axis direction to form a large-area electrode structure, and the spraying process is repeated to obtain a desired loading. An LTO loading of 5 mg _LTO cm ^-2 can be obtained by nozzle sweeping 20 times at 0.2 cm s ^-1 . A layer of about 15 μm thick LTO/AgNW (or CNT) is loaded onto a 16 μm thick PET MF mat, and the 16 μm thick PET MF mat is LTO and AgNW (or CNT) on the MF surface and in the inner MF pores. ) Are combined with each other.

In (c) of FIG. 1, the deformation process of twisting and folding of the LTO-loaded AgNW$MF electrode was performed, but no serious damage was observed in appearance. In general, a metal foil loaded with an active material layer is used as a current collector for efficient electron supply. On the other hand, the present invention can provide an electrode structure having a 3D interconnection network having high electrical conductivity without a current collector and a polymer binder.

In Figure 1 (d), the electrical conductivity of the LTO-loaded AgNW$MF and LTO-loaded CNT#MF electrodes is four times that of the slurry-coated active layer containing LTO, carbon black and a binder (including an aluminum current collector), and It can be seen that it has increased significantly by 2 times. Also,

This is because the conductivity of AgNW$MF is higher than that of CNT#MF, which reduces the contact resistance between the NWs and the interlocking joints formed due to (1) the high electrical conductivity of Ag and (2) the ductile properties of Ag. It is due to a decrease. Thus, LTO-containing AgNW$MF can be used as an independent anode.

In Fig. 1(e), the absence of a current collector reduces the volume and weight of the electrode, which provides more improved volumetric and gravimetric energy densities. For example, when replacing an electrode including an active material layer on a conventional current collector with a standalone AgNW$MF electrode containing an active material ((5 mg _LTO cm ^-2 ), 53% (58 μm) to 31 μm Reduction) and a weight reduction of 70% can be achieved.

The flexibility (fexibility) and foldability (foldability), the cohesive force between the constituent materials of the electrode and the adhesion between the active material and the substrate are important factors for mechanical durability. This can be quantified by measuring the mass of the electrode during the cohesion and/or adhesion cycle.

Figure 2 shows the effect of deformation by folding in the weight, microstructure and electrical properties of LTO-loaded AgNW$MF and CNT#MF electrodes. Unless otherwise stated, LTO loading = 5 mg _LTO cm ^-2 . A layer of about 5 μm thick LTO/AgNW (or CNT) is loaded onto a 16 μm thick PET MF mat where LTO and AgNW (or CNT) are bound to the surface of the MFs or to the inner-MF pores. a) the change in the relative weight of the electrode after 1000 folding cycles, b) the change in electrical resistance according to the folding cycle. Three types of LTO loading were used for CNT#MF. R0 and R represent the electrical resistance before and after folding, respectively. cf) is the SEM image, c) is the position where the SEM image is measured, and df) the top view of LTO-loaded AgNW$MF: d) before folding, e) after 500 folding cycles, and f) after 1000 folding cycles , gj) Top view of LTO-loaded CNT#MF: g) Before folding (5 mg _LTO cm ^-2 ), h) 5 mg _LTO cm ^-2 after 250 folding cycles, i) After 600 folding (1 mg _LTO cm ^-2 ) and j) after 1000 folding cycles (0.5 mg _LTO cm ^-2 ).

In Figure 2 (a), the NW@MF structure including AgNW$MF and CNT#MF did not observe any reduction in electrode weight in 1000 folding cycles in the absence of electrolyte and 200 folding cycles in the presence of electrolyte. . This shows that NWs (AgNW or CNT) successfully bind LTO particles to PET MFs, although no binder was used. On the other hand, in a structure having an active layer on a type of current collector, 40% of the weight of the active layer (including LTO, carbon black, and binder polymer) fell from the aluminum current collector after 100 folding cycles. That is, this means that the active layer containing the binder is easily peeled off from the metal current collector. After the repetitive folding cycles in FIGS. 2 (b) to (j), the interconnected LTO/AgNW network structure slightly changed, but the electrical resistance of LTO-loaded AgNW$MF (5 mg _LTO cm ^-2 ) No change was observed even after 1000 folding cycles. In addition, it can be seen that CNT#MF (5 mg _LTO cm ^-2 ) having the same LTO loading density rapidly increases the electrical resistance in the initial folding cycle and cracks occur in 250 folding cycles (Fig. 2 h). . That is, when CNT#MF is reduced to 1/10 (0.5 mg _LTO cm ^-2 ) of the above-mentioned loading density, it has durability over 1000 folding cycles (Fig. 2b). At 5 mg cm ^-2 , LTO-loaded AgNW$MF lost the 1D characteristic of AgNWs on the electrode surface, but showed a slight increase in resistance by repeated folding. This is because aggregation of AgNWs occurs on the edge surface of the folded portion after 1000 folding cycles. The stress-strain curves of bare PET mat (MF), AgNW$MF, and CNT#MF were measured using a tensile strength machine, and Young's modulus and "yield strength defining elastic region" Increased by MFs wrapped in silver, AgNW or CNT: Young's modulus increased from 2.6 MPa for MF to about 4 MPa for NW@MF: yield strength was about 0.62 MPa for MF and about for NW@MF. Increased to 1.7 MPa.

FIG. 3 shows the lithiation/delithiation electrochemistry of LTO compared with a conventional structure (LTO|Al) including an NW@MF structure and an active layer on a current collector.

3 is a lithium electrochemical characteristic of AgNW$MF, CNT#MF and LTO loaded on an aluminum foil, and the configuration of the electrode structure is shown in FIG. 1. Half-cells containing lithium metal were used as panels (a) to (c) having a potential in the range of 1 to 3 V. The pouch cell is made of 5 cm x 3 cm and has an energy density at 3 mAh cm ^-2 for panels (d) to (f). a) Capacity is maintained by repetition of charging and discharging at 1 C. The capacity was leveled by the weight of the LTO in g _LTO (upper position) and the total weight (g _ED ) including the electrode and the current collector (lower position). b) Rate capabilities. c) Differential capacities (dQ/dV) curves at 1 C. d) Capacity retention of folded AgNW$MFs (2L and 4L) versus unfolded AgNW$MFs (1L) by repetition of charging and discharging at 1 C, and the capacity is the weight of LTO in g _LTO or geometric electrode area (cm ² ) Leveled by e) the capacity ratio of folded AgNW$MFs, and f) the capacity retention of the folded battery at different angles at 1 C.

There is no difference in the gravimetric capacity per LTO weight (mAh g _LTO ^-1 ) between the two NW@MF and the conventional structure (Al) at the top of (a) of FIG. 3, which is within the NW@MF structure. It means that the capacity of LTO is effectively utilized. From the bottom of Fig. 3 (a), it can be seen that the weight of AgNW$MF and CNT#MF per electrode weight in the electrode capacity (mAh g _ED ^-1 ), ED = electrode) is increased by more than 4 times compared to the conventional electrode. have. This is because the independent structure has an advantage in weight reduction since it does not include a current collector. In (b) of FIG. 3, it can be seen that the high conductivity of AgNW$MF of LTO improves the rate capability of LTO included in the electrode. In Fig. 3(c), the fast electrochemical dynamics of the LTO-loaded AgNW$MF electrode are clearly presented by the differential capacity (dQ/dV) curve.

Based on the durability of AgNW$MF during folding in (e) of FIG. 3, folded LTO-loaded AgNW$MFs were used as electrodes of flexible lithium-ion batteries (LIBs), and total electrodes per geometric area The capacity can be easily controlled by folding a strip of highly flexible AgNW$MF. For example, the area capacity of the 4-layer (4L) AgNW$MF obtained by folding AgNW$MF in half in FIG. 3(d) is more than 4 times higher than that of the unfolded (1L) AgNW$MF . As it does not reduce the weight capacity per LTO weight, the LTO capacity of conventional slurry coated LTO|Al and 1L, 2L, and 4L AgNW$MF is equal to about 150 mAh g _LTO- ¹ . The interconnected network of AgNWs connecting the inner fiber pores of the MF matrix and the periphery of the MFs ensures electrical conductivity and ion transport, respectively, even after folding.

In (e) of FIG. 3, since a longer Li+ material transfer path is required in order to make the most of the active material in the more stacked electrode, the more stacked electrode shows a low rate capabilities. In addition, the higher capacity of the LIB cell at a fixed size is realized over all discharge rates using folded electrodes.

In FIG. 3 (f), the pouch-type LTO half-cell based on the NW@MF structure shows excellent capacity retention under static bending conditions.

Figure 4. Regarding a bent highly flexible battery consisting of LTO-loaded AgNW$MF and LFP-loaded CNT#MF (AgNW$MF|LTO||LFP|CNT#MF), a) highly flexible battery, b) before bending And the open circuit voltage of the subsequent LTO||LFP battery, c) Red LEDs driven by NW@MF-based LTO||LFP under folding, bending and hammering, d) 1L- and 4L-based LTO| at 1 C. |Voltage profile of LFP, e) capacity retention at 1 C. The cells were folded 20 times with every 20 charge/dust-proof cycles. f) It shows the comparison between the flexible battery and the 4L-NW@MF-based battery reported in area capacity and bending radius.

In Figure 4 (a), the superflexible pouch-type full cells are LFP (lithium iron phosphate) loaded on CNT#MF as a cathode, and LTO-loaded structure on AgNW$MF as an anode. (AgNW$MF|LTO||LFP|CNT#MF). The anode-to-cathode capacity ratio (N/P ratio) is fixed at about 1.2. The weight ratio is equal to the N/P ratio, which is the LFP. This is because the capacity is close to LTO CNTs are used as cathodes, because AgNW is oxidized at the cathode potential of LIBs LTO-loaded AgNW$MF and LFP-loaded CNT#MF are 100 of charge and discharge at 1 C. No morphological transformation was observed after the cycle.

4(c) the highly flexible NW@MF-based battery continuously supplied power to the LEDs without any intermittent interruption during repetitive hammering of the folded edge, multiple folds, and folding up to 100 times.

When the fully charged double-treated whole cell was severely crumpled, the open-circuit voltage (OCV) of the NW@MF based LTO||LFP cell was not charged to the full (1.85 V). The OCV of the conventional battery based on the active layer-foil structure dropped from 1.85 to 0.0335 V, and did not recover to the initial value even after the crumpled battery was opened again.

In (d) of FIG. 4, the use of the 4L electrode in both the cathode and anode of the highly flexible NW@MF-based battery (4L-AgNW$MF and 4L-CNT#MF) increased the capacity by four times. The potential profiles of the 1L- and 4L-based LTO||LFP cells do not differ in size. This means that 4L-based cells do not have serious problems with respect to charge transport or mass transfer.

In the case of folding and unfolding intermittently 20 times in every 20 discharge/charge cycles in (e) of FIG. 4, there is no difference between the 1L and 4L batteries in capacity retention during the discharge/charge cycle.

It provides a higher active material loading (3.2 mA h cm ^-2 ) compared to the foldable LIB battery reported in FIG. 4(f), and can successfully realize LIB operation under extreme bending conditions (bending radius = 1 mm). have.

(REF 17: A. M. Gaikwad, B. V. Khau, G. Davies, B. Hertzberg, D. A. Steingart, A. C. Arias, Adv. Energy Mater. 2015, 5, 1401389.

REF 42: J.-G. Wang, D. Jin, R. Zhou, X. Li, X.-r. Liu, C. Shen, K. Xie, B. Li, F. Kang, B. Wei, ACS Nano 2016, 10, 6227.

REF 43: Z. Song, T. Ma, R. Tang, Q. Cheng, X. Wang, D. Krishnaraju,

R. Panat, C. K. Chan, H. Yu, H. Jiang, Nat. Commun. 2014, 5,3140.

REF 44: Q. Cheng, Z. Song, T. Ma, B. B. Smith, R. Tang, H. Yu, H. Jiang, C. K. Chan, Nano Lett. 2013, 13, 4969.

REF 45: M. Koo, K.-I. Park, S. H. Lee, M. Suh, D. Y. Jeon, J. W. Choi, K. Kang, K. J. Lee, Nano Lett. 2012, 12, 4810.

REF 46: L. Hu, H. Wu, F. La Mantia, Y. Yang, Y. Cui, ACS Nano 2010, 4,

5843.

REF 47: Z. Chen, J. W. F. To, C. Wang, Z. Lu, N. Liu, A. Chortos, L. Pan, F. Wei, Y. Cui, Z. Bao, Adv. Energy Mater. 2014, 4, 1400 207.

REF 48: H. Lee, J.-K. Yoo, J.-H. Park, J. H. Kim, K. Kang, Y. S. Jung, Adv. Energy Mater. 2012, 2, 976.)

That is, in the results of FIGS. 1 to 4, it has excellent mechanical durability without any increase in resistance even after 1000 repetitive folding and test, and the energy density per area is easily controlled by the number of folded stacks of the electrode mat. An electrode structure that can be formed and a lithium ion battery including the same can be provided. In addition, deformable lithium-ion batteries of lithium titanium oxide as an anode and lithium iron phosphate as a cathode at a high capacity per area (3.2 mAh cm ^-2 ) are charged. And it can be seen that the operation is performed without deterioration in performance and structural destruction even after repeated wrinkles and folding during discharge, and continuous LED driving is realized using this.

The present invention not only provides flexible LIBs with excellent current collector-free and binder-free nanowire-around-microfiber (NW@MF) architectures surrounded by nanowires. In addition, LIBs can also provide capacity scaling flexibility in manufacturing. In the present invention, NW@MFs was provided as AgNW-wound PET MFs (AgNW$MF) and CNT-webbed PET MFs (CNT#MF). Within NW@MFs, NWs (AgNW or CNT) secure 3D interconnected structures under multiple mechanical stresses by bending, folding and crumpling, and provide an electrically conductive path for active materials. do. The LTO-loaded AgNW$MF electrode exhibits very good mechanical durability as well as high loading density (mass loading, 5 mg _LTO cm ^-2 ), which is 82 mAh g _LTO ^-1 and 58 mAh g _ED ^-1 at 50 C. It provides excellent capacity retention rates of 150 mAh g _LTO ^-1 and 93 mAh g _ED ^-1 at 1 C after 1,000 cycles with improved rate capabilities. Due to their excellent flexibility and durability, a folded NW@MF electrode loaded with an active material can be effectively used in LIBs, and the total electrode capacity per geometric area can be easily controlled by folding a very flexible strip of NW@MF. The LTO-loaded AgNW$MF folded twice (4L) in a half cell is an unfolded electrode (150 mAh g _LTO ^-1 ), which shows the same capacity per mass of LTO, and its capacity per area is an unfolded electrode (3.2 versus 0.8). mAh cm ^-2 at 1 C after 1000 cycles). In bending, wrinkle and hammering (hammering) realized the operation of the full cells (full cells) containing LTO-loaded AgNW$MF and LFP-loaded CNT#MF, these experimental results, according to the present invention NW@MF- It shows that the base electrode structure is applicable to other flexible devices such as LEDs.

As described above, although the embodiments have been described by the limited drawings, a person of ordinary skill in the art can apply various technical modifications and variations based on the above. For example, the described techniques are performed in a different order from the described method, and/or components such as a system, structure, device, circuit, etc. described are combined or combined in a form different from the described method, or other components Alternatively, even if substituted or substituted by an equivalent, an appropriate result can be achieved.

Therefore, other implementations, other embodiments and claims and equivalents fall within the scope of the following claims.

Claims (20)

Micro fiber based substrates; And
A functional material coated on the substrate;
Including,
The functional material, an active material; And at least one of a metal nanowire, a carbon nanowire, a carbon fiber, and a carbon nanotube; and
The substrate includes 1 um to 20 um pore size, 20% to 60% porosity, and 10 um to 30 um thickness,
The substrate has a liquid wettability of a contact angle of 50 degrees or less,
The functional material may include at least one of carbon nanowires, carbon fibers, and carbon nanotubes; And an active material; Including, at least one of the carbon nanowires, carbon fibers and carbon nanotubes: substrate: active material, 1:1.2 to 2:1.5 to 5 (mass ratio) or
The functional material includes a metal nanowire and an active material, and the metal nanowire: base: active material is included in a ratio of 1:1.2 to 2:1.5 to 5 (mass ratio),
The active material, 50 nm to 500 nm containing nano-sized particles,
Foldable electrode structure.
The method of claim 1,
The foldable electrode structure has a loading density of 1 mg/cm ² or more of a functional material in the substrate,
Foldable electrode structure.
The method of claim 1,
The functional material is wound or webbed with the microfiber to form a coating layer by a three-dimensional network network,
The active material is trapped in the three-dimensional network network,
The functional material is to form a coating layer with a thickness of 10% or more of the thickness of the substrate,
Foldable electrode structure.
The method of claim 1,
The functional material is impregnated with 10% or more of the thickness direction of the substrate,
Foldable electrode structure.
delete delete The method of claim 1,
The functional material further comprises at least one carbon-based material selected from the group consisting of graphite particles, expanded graphite particles, hard carbon particles, soft carbon particles, graphene, acetylene black and Ketjen black,
Foldable electrode structure.
The method of claim 1,
The metal nanowires include at least one selected from the group consisting of transition metals, precious metals, rare earth metals, oxides thereof, and alloys thereof,
Foldable electrode structure.
delete The method of claim 1,
The substrate includes microfibers having a diameter of 1 um to 100 um,
The microfibers include natural fibers, polymer fibers or both,
The polymer fibers are cellulose fibers, polyacrylic acid (PA), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polypropylene terephthalate (PPT), polyacrylonitrile (PAN). ), nylon, polyethylene naphthalate (PEN), polyethersulfone (PES), polyetheretherketone (PEEK), polyphenyrene sulfide (PPS), polyvinylidene fluoride (PVDF), polysulfone (PSU) ), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), polyurethane (PU), and polystyrene (PS) comprising at least one selected from the group consisting of,
Foldable electrode structure.
The method of claim 1,
The active material is (Li (Ni, Co, Al)O ₂ ) based active material (NCA), Li(Ni, Mn, Co)O ₂ based active material (NMC), lithium cobalt oxide based active material (lithium cobalt oxide, LCO) , Lithium iron phosphate (LFP), lithium titanium oxide (LTO), lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate active material (lithium aluminum germanium phosphate, LAGP) containing at least one selected from the group consisting of,
Foldable electrode structure.
A flexible device comprising an electrode formed to include the foldable electrode structure of claim 1.
Microfiber-based substrate for negative electrode; And a metal nanowire for a negative electrode coated on the microfiber-based substrate for the negative electrode. And an anode active material for an anode; And
Microfiber-based substrate for positive electrode; A carbon-based material for the positive electrode of at least one of carbon nanowires, carbon fibers, and carbon nanotubes coated on the microfiber-based substrate for positive electrode; And a positive electrode structure comprising; and an active material for a positive electrode,
Each of the cathode structure and the anode structure includes the foldable electrode structure of claim 1,
Flexible device.
The method of claim 12 or 13,
The device includes at least one or more of display, mobile, energy conversion and energy storage functions,
Flexible device.
The method of claim 14,
The device is a lithium ion battery, the flexible device.
Preparing a microfiber-based substrate; And
Coating a functional material solution by ultrasonic spraying on the substrate;
Including,
The functional material, an active material; And at least one of a metal nanowire, a carbon nanowire, a carbon fiber, and a carbon nanotube; and
The substrate has a liquid wettability of a contact angle of 50 degrees or less,
The step of coating by ultrasonic spraying is performed by ultrasonic spraying at a temperature of 50° C. to 100° C. at 60 to 120 ultrasonic energy (kHz) and a speed of 1 to 10 (ml/min),
Further comprising the step of compressing the coated substrate,
The pressing step is to compress at a temperature of 20 ℃ to 60 ℃ and pressure of 1bar to 10bar,
Method of manufacturing a foldable electrode structure.
delete The method of claim 16,
The step of coating by ultrasonic spraying is that the spraying head moves while linearly moving or swinging in the X and Y axis directions,
Method of manufacturing a foldable electrode structure.
delete The method of claim 16,
In the functional material solution, the metal nanowire to the active material is included in a ratio of 1:1 to 1:20 (mass ratio), or
At least one of carbon nanowires, carbon fibers, and carbon nanotubes in the functional material solution; The active material is contained in a 1:1 to 1:20 (mass ratio),
Method of manufacturing a foldable electrode structure.

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