JP6959328B2 - Humic acid bonded metal foil film current collector and battery and supercapacitor containing the current collector - Google Patents

Description

Cross-reference to related applications This application claims priority over US patent applications 15/243589 and 15/2436606 filed on August 22, 2016, respectively, with reference to the contents of the specification of the present application. Incorporate into.

The present invention provides a current collector for a lithium battery or supercapacitor. The current collector is a metal foil to which a thin film of highly oriented humic acid or a highly conductive graphite film derived from humic acid is bonded.

This patent application applies to lithium cells (eg lithium ion cells, lithium-metal cells, or lithium ion capacitors), supercapsules, non-lithium batteries (eg zinc-air cells, nickel metal hydride batteries, sodium ion cells, and magnesium ions). The purpose of the current collector is to act together with the anode electrode (anode active material layer) or cathode electrode (cathode active material layer) of the cell) and other electrochemical energy storage cells. This application is not part of the anode active material layer or the cathode active material layer itself.

Lithium-metal cells include conventional lithium-metal rechargeable cells (eg, using lithium foil as the anode and MnO ₂ particles as the cathode active material), lithium-air cells (Li-Air), lithium-sulfur cells (eg, Lithium-sulfur cells). Li-S), and advanced lithium-graphene cells (using a graphene sheet as the cathode active material, Li-graphene), lithium-carbon nanotube cells (using CNT as the cathode, Li-CNT), and lithium-nanocarbon. Cells (Li-C, which use nanocarbon fibers or other nanocarbon materials as the cathode) are included. The anode and / or cathode active material layer can contain some lithium or can be prelithiumized before or immediately after cell assembly.

Rechargeable Lithium Ion (Li Ion), Lithium Metal, Lithium-Sulfur, and Li Metal-Pneumatic Batteries are electric vehicles (EVs), hybrid electric vehicles (HEVs), and portable electronic devices such as laptop computers and mobile phones. It is considered to be a promising power source for telephones. Lithium as a metal element is highest compared to any other metal or metal-intercalated compound as an anode active material ( _{excluding Li 4.4 Si, which has a specific capacity of 4,200 mAh / g).} It has a lithium storage capacity (3,861 mAh / g). Therefore, in general, Li metal batteries (with lithium metal anodes) have a significantly higher energy density than conventional lithium ion batteries (with graphite anodes).

Traditionally, rechargeable lithium metal batteries have a relatively high specific capacity, such _{as TiS 2} , MoS ₂ , MnO ₂ , CoO ₂ , and V ₂ O ₅ , as cathode active materials that are combined with a lithium metal anode. Manufactured using non-lithiumized compounds with. When the battery was discharged, lithium ions were transferred from the lithium metal anode to the cathode through the electrolyte, and the cathode was lithium-ized. Unfortunately, upon repeated charging and discharging, the lithium metal formed dendritic crystals on the anode that ultimately resulted in internal short circuits, thermal runaway, and explosions. As a result of a series of accidents related to this problem, the production of these types of secondary batteries was discontinued in the early 1990s and replaced by lithium-ion batteries. Even today, cycle stability and safety issues remain major obstacles to further commercialization of Li metal batteries (eg, lithium-sulfur and lithium-transition metal oxide cells) for EV, HEV, and microelectronic device applications. It is the cause.

Inspired by the aforementioned issues regarding the safety of preceding lithium metal secondary batteries, lithium ion secondary batteries have been developed, where high-purity lithium metal sheets or films are used as anode active materials in carbonaceous materials (eg natural). It was replaced by a graphite particle). The carbonaceous material absorbs lithium (eg, by intercalation of lithium ions or atoms between the graphene surfaces) and desorbs lithium ions during each of the recharge and discharge stages of lithium ion battery operation. The charcoal material may primarily contain graphite capable of intercalating lithium, the resulting graphite interlayer compound may _{be represented as Li x} C ₆ , where x is typically less than 1 (graphite). The specific volume of is <372 mAh / g).

While lithium-ion (Li-ion) batteries are promising energy storage devices for electric-powered vehicles, state-of-the-art Li-ion batteries offer cost, safety, and performance goals (eg, high specific energy, high energy density, good). Cycle stability and long cycle life) have not yet been met. Li ion cells typically use a lithium transition metal oxide or phosphate as the positive electrode (cathode) that de-/ ^{reintercalates Li +} at a high potential with respect to the carbon negative electrode (anode). The specific volume of the lithium transition metal oxide or phosphate-based cathode active material is typically in the range of 140-170 mAh / g. As a result, the specific energy (mass energy density) of commercially available Li ion cells characterized by graphite anodes and lithium transition metal oxides or phosphate cathodes is typically 120-220 Wh / kg, most typically 150-200 Wh /. It is in the range of kg. A corresponding typical range of energy densities (volumetric energy densities) is 400-550 Wh / L. The energy density is even lower under high charge-discharge rate conditions. These specific energy values are one-half to one-third of the specific energy values required if battery-powered electric vehicles are widely accepted.

A typical battery cell is an anode electrode (typically an anode active material, a conductive filler, and a binder resin) bonded to the anode current collector with (a) an anode current collector and (b) a binder resin. (Also referred to as an anode active material layer containing components), (c) electrolyte / separator, (d) cathode electrode (typically containing a cathode active material, a conductive filler, and a binder resin). (Also called a cathode active material layer), (e) a cathode current collector bonded to the cathode electrode with a binder resin, (f) a metal tab connected to an external wiring, and (g) everything else except the tab. Consists of a casing that wraps around the components of.

The current collector, typically aluminum foil (cathode side) and copper foil (anode side), accounts for about 15-20% by weight of the lithium-ion battery and 10-15% at cost. Therefore, thinner, lighter foils are preferred. However, there are some major issues associated with state-of-the-art current collectors:
(A) Thinner foils tend to be more expensive and more difficult to work with because they are easily creases and tears. (B) The current collector must be electrochemically stable with respect to the cell components with respect to the action potential window of the electrode. In practice, continuous corrosion of the current collector, predominantly by electrolytes, can lead to a gradual increase in the internal resistance of the battery, which can lead to a persistent decrease in apparent capacity. (C) Oxidation of the metal current collector is a strong exothermic reaction that can significantly contribute to the thermal runaway of the lithium battery.

Therefore, current collectors are crucial for battery cost, weight, safety, and performance. Instead of metal, graphene or graphene-coated solid metals or plastics are considered as promising current collector materials, as summarized in the references described below:
1. 1. Li Wang, Xiangming He, Jianjun Li, Jian Gao, Mou Fang, Guangyu Tian, Gianlong Wang, Shoushan Fan, "Graphene-coated plastic film / lithium sulfur battery" Power Source, 239 (2013) 623-627.
2. S. J. Richard Prabakar, Yun-Hwa Hwang, En Gyoung Bae, Dong Kyu Lee, Myungho Pyo, “Graphene oxide as a corrosion in-charge)
3. 3. Yang Li, et al. Chinese Patent Pub. No. CN 104600320 A (2015, 05, 06).
4. Zhaoping Liu, et al (Ningbo Institute of Materials and Energy, China), WO 2012/151880 A1 (Nov.15, 2012).
5. Gwon, H. et al. Kim, HS; Lee, KE; Seo, DH; Park, YC; Lee, Y-S; Ahn, BT; Kang, K "Flexible energy storage technology based on graphene technology" 4 (2011) 1277-1283.
6. Ramesh C.I. Bardwaj and Richard M. Mank, "Graphene current collectors in batteries for portable electronics devices", US 20130595389 A1, Apr 18, 2013.

Recently, graphene current collectors come in three different forms: graphene-coated substrates [References 1-4], free-standing graphene paper [References 5], and transition metal (Ni, Cu) catalysts. A single-layer graphene film produced by chemical vapor deposition (CVD) and subsequent metal etching [Reference 6].

In the preparation of graphene-coated substrates, a small separation sheet or plate lit of graphene oxide (GO) or reduced graphene oxide (RGO) is spray deposited onto a solid substrate (eg, plastic film or Al foil). In the graphene layer, the components are separated graphene sheets / plate lits (typically 0.5-length / width) typically joined by a binder resin, eg PVDF [references 1, 3 and 4]. 5 μm and thickness 0.34-30 nm). The single graphene sheet / plate lit can have a relatively high electrical conductivity (within its 0.5-5 μm range), whereas the resulting graphene-binder resin composite layer has a relatively high electrical conductivity. Low (typically <100 S / cm and more typically <10 S / cm). Furthermore, another purpose of using the binder resin is to bond the graphene-binder composite layer to a substrate (eg Cu foil), which is between the Cu foil and the graphene-binder composite layer. It means that there is a binder resin (adhesive) layer. Unfortunately, this binder resin layer is electrically insulating, and the resulting adverse effects appear to have been totally overlooked by previous researchers.

Prabakar et al. [Reference 2] appear to have not used a binder resin to form the aluminum foil coated with the discrete graphene oxide sheet, but this graphene oxide coated Al foil is a problem of its own. Has. It is known in the art that aluminum oxide (Al ₂ O ₃ ) is immediately formed on the surface of the aluminum foil and cleaning with acetone or alcohol cannot remove this passivation layer of aluminum oxide or alumina. Is. Not only is this aluminum oxide layer electrically and thermally insulating, it is not really resistant to certain types of electrolytes. For example, the most commonly used electrolyte for lithium-ion batteries is LiPF ₆ dissolved in an organic solvent. A small amount of H ₂ O in this electrolyte causes a series of chemical reactions accompanied by the formation of HF (highly corrosive acid) that quickly decomposes the aluminum oxide layer and corrodes the Al foil and continues to consume the electrolyte. be able to. The reduction in capacity is typically quite apparent after a 200-300 charge-discharge cycle.

Free-standing graphene paper is typically made by vacuum-assisted filtration of GO or RGO sheets / plate lit suspended in water. In self-supporting paper, the component is a separate graphene sheet / plate lit that loosely overlaps together. Also, single graphene sheets / plate lits can have relatively high electrical conductivity (within the range of 0.5-5 μm), while the resulting graphene paper has very low electrical conductivity, eg 8, It has 000 S / m or 80 S / cm [Reference 5], which is four orders of magnitude lower than ^{the conductivity of Cu foil (8 × 10 5 S / cm).}

There are some major problems with the most commonly used methods for producing graphene (ie chemical oxidation / intercalation methods):
(1) The method requires the use of large amounts of some unwanted chemicals such as sulfuric acid, nitric acid, and potassium permanganate and / and sodium chlorate.
(2) Thermal delamination requires high temperatures (typically 800-1,050 ° C.) and is therefore a highly energy intensive process.
(3) This method requires a very time-consuming, lengthy cleaning and purification process. For example, typically washing with 2.5 kg of water to recover 1 gram of GIC results in a very large amount of wastewater that needs to be properly treated.
(4) The product obtained is a graphene oxide (GO) plate lit that must undergo an additional chemical reduction treatment to reduce the oxygen content. Typically, even after reduction, the electrical conductivity of GO plate lit remains much lower than that of pure graphene. In addition, reduction procedures often require the use of toxic chemicals such as hydrazine.
(5) Further, the amount of intercalation solution retained on the flakes after drainage ranges from 20 to 150 parts by weight (pph) of solution per 100 parts by weight of graphite flakes and more typically from about 50 to 120 pph. There may be. During exfoliation, the residual intercalate species retained by the flakes decompose _{to produce various species of sulfur and nitrite compounds (eg, NO x} and SO _x ), which are undesirable. Waste liquid requires costly improvement procedures to avoid unfavorable environmental impacts.

The catalytic CVD method for graphene production requires the introduction of hydrocarbon gas into a vacuum chamber at a temperature of 500-800 ° C. Under these harsh conditions, the hydrocarbon gas is decomposed by a decomposition reaction catalyzed by a transition metal substrate (Ni or Cu). The Cu / Ni substrate is then chemically etched using a strong acid, which is not an environmentally friendly procedure. The entire process is slow, lengthy and energy intensive, and the resulting graphene is typically single-layer or multi-layer graphene (because the underlying Cu / Ni layer loses its effectiveness as a catalyst). , Up to 5 layers).

Bardwaj et al. [Reference 6] proposed stacking multiple CVD-graphene films to a thickness of 1 μm or several μm. However, this requires hundreds or thousands of films to be stacked together (each film is typically 0.34 nm to 2 nm thick). Bardwaj et al. Claim that "graphene may reduce manufacturing costs and / or increase the energy density of battery cells," but did not provide experimental data to support their claims. Contrary to this claim, CVD graphene is a widely known method of cost, assuming that even a single layer of CVD graphene film is given the same area (eg, the same 5 cm x 5 cm). It will cost considerably more than a sheet of Cu or Al foil. A laminate of hundreds or thousands of single-layer or multi-layer graphene films as proposed by Bardwaj et al. Means that it costs hundreds or thousands of times more than a Cu foil current collector. This cost is exorbitantly high. In addition, the high contact resistance between the hundreds of CVD graphene films in the laminate and the relatively low conductivity of the CVD graphene results in high total internal resistance, resulting in a thinner film (1 μm graphene laminate for 10 μm Cu foil). The body) is used to completely waste the potential benefit of reducing the total weight and volume of the cell. It is considered that the patent application [Reference 6] of Bardwaj et al., Which does not contain any data, is nothing but a conceptual paper.

The above discussion clearly shows that all three forms of graphene-enhanced or graphene-based current collectors do not meet the performance and price requirements for use in batteries or supercapacitors. There is a great need for different types of materials for use as current collectors.

The present invention is directed to a new class of materials referred to herein as highly oriented films that are chemically bonded to the surface of a metal foil, either humic acid (HA) alone or in combination with graphene. The graphenes used herein include pure graphene, graphene oxide, graphene fluoride, graphene nitrogenated, graphene hydride, boron-doped tographene, any other type of doped tografene, and other types of chemically Includes functionalized graphene. Quite unexpectedly and importantly, this highly oriented film of HA or HA / graphene mixture can be thermally converted to a highly conductive graphite film.

Humic acid (HA) is an organic substance commonly found in soil and can be extracted from soil using a base (eg KOH). HA can also be extracted in high yield from a type of coal called leonardite, another highly oxidized form of lignite coal. HA extracted from leonaldite contains a large number of oxygenating groups (eg, carboxyl groups) located around the edges of ^{a molecular center (SP 2 core of hexagonal carbon structure) such as graphene.} This material is a bit like graphene oxide (GO) produced by strong acid oxidation of natural graphite. HA has a typical oxygen content of 5% to 42% by weight (other major elements are carbon and hydrogen). HA has an oxygen content of 0.01% to 5% by weight after chemical or thermal reduction. For the definition of claims in the present application, humic acid (HA) is based on the entire range of oxygen content of 0.01% by weight to 42% by weight. Reduced humic acid (RHA) is a special type of HA with an oxygen content of 0.01% to 5% by weight.

It is surprising to discover that humic acid can be chemically bonded to a metal foil when it is brought into close contact with the surface of the metal foil. It is even more surprising to discover that when properly aligned and packed together, the humic acid molecules can be chemically linked to each other to give a longer and wider humic acid sheet. .. Also, these humic acid molecules can be chemically linked or bonded to the graphene sheet when present and when properly aligned and packed. The resulting fumic acid-bonded or graphite-film-bonded thin metal foil is electrolyte-compatible, non-reactive, corrosion-proof, low-contact resistance, thermally conductive and electrically conductive, ultra-thin, and lightweight, making the battery or capacitor more It allows for higher output voltage, higher energy density, higher rate capacity, and much longer cycle life.

The present invention provides a highly oriented humic acid bonded metal foil current collector for use in batteries or supercapacitors. The present invention also provides a current collector composed of a metal foil and a humic acid-derived highly conductive graphite film bonded to one or two primary surfaces of the metal foil. The present invention also provides a method for manufacturing these current collectors.

The current collector of the present invention is (a) a thin metal foil having a thickness of 1 μm to 30 μm (preferably 4 μm to 12 μm) and two opposed substantially parallel primary surfaces, and (b) two opposing metal foils. With at least one thin film (or highly conductive graphite film obtained from this thin film) of highly oriented fumic acid (HA) or a mixture of HA and a graphene sheet that is chemically bonded to at least one of the primary surfaces. include. A thin film of HA or HA / graphene mixture or the resulting graphite film has a thickness of 10 nm to 10 μm, an oxygen content of 0.01% to 10% by weight, a physics of ^{1.3 to 2.2 g / cm 3.} Target density, hexagonal carbon planes oriented substantially parallel to each other and parallel to the primary surface, interplanetary spacing of 0.335 to 0.50 nm between hexagonal carbon planes, measured alone without the thin metal foil. It has a thermal conductivity greater than 250 W / mK (more typically> 500 W / mK) and an electrical conductivity greater than 800 S / cm (more typically> 1,500 S / cm).

Preferably, each of the two opposing primary surfaces is chemically bonded to such a thin film of humic acid or HA / graphene mixture produced by heat treatment or a graphite film obtained from this thin film. Also preferably, one or both of the thin films of HA or both HA and graphene (or the resulting graphite film) are on one or both opposite primary surfaces of the metal foil without the use of binders or adhesives. Chemically bonded. When a binder is used, the binder is an electrically conductive material selected from essentially conductive polymers, pitches, amorphous carbons, or carbonized resins (polymer carbons). Preferably, the thin metal foil has a thickness of 4-12 μm. Also preferably, a thin film or graphite film of humic acid or HA / graphene mixture has a thickness of 20 nm to 2 μm.

For the current collector, the metal foil is preferably selected from Cu, Ti, Ni, stainless steel, Al foil, or a combination thereof. Preferably, the primary surface does not contain a layer of passivated metal oxide on it (eg, does not have _{alumina, Al 2} O _{3 on the Al foil surface).}

Preferably, the thin film of HA or HA / graphene mixture or the graphite film obtained from it has an oxygen content of 1% to 5% by weight. More preferably, the thin film or the graphite film obtained from it has an oxygen content of less than 1%, an interplane spacing of less than 0.345 nm, and an electrical conductivity of 3,000 S / cm or more. More preferably, the thin film or the graphite film obtained from it has an oxygen content of less than 0.1%, an interplane spacing of less than 0.337 nm, and an electrical conductivity of 5,000 S / cm or more. Even more preferably, the thin film or the graphite film obtained from it has an oxygen content of 0.05% or less, an interplane spacing of less than 0.336 nm, a mosaic spread value of 0.7 or less, and 8,000 S / cm or more. Has electrical conductivity of. Even more preferably, the thin film or the graphite film obtained from it has an interplane spacing of less than 0.336 nm, a mosaic spread value of 0.4 or less, and an electrical conductivity of greater than 10,000 S / cm.

More preferably, a thin film of HA or HA / graphene mixture or a graphite film obtained from it exhibits an interplane spacing of less than 0.337 nm and a mosaic spread value of less than 1.0. Most preferably, the thin film e or the graphite film obtained from it exhibits a graphitization degree of 80% or more and / or a mosaic spread value of 0.4 or less.

In certain embodiments, a thin film of HA or HA / graphene mixture deposits a suspension of HA or a mixture of HA and graphene sheet on the at least one primary surface under the influence of orientation control stress. It is obtained by a step of forming a layer of HA or a mixture of HA and a graphene sheet, and then a step of heat-treating the layer at a heat treatment temperature of 80 ° C. to 1,500 ° C. More preferably, the heat treatment temperature is 80 ° C. to 500 ° C., and even more preferably 80 ° C. to 200 ° C.

As shown in FIG. 3C, the highly oriented thin film of HA or HA / graphene bonded to the underlying current collector or the graphite film obtained from it is typically a chemically bonded fumic acid molecule or chemistry. It contains assimilated fumic acid and graphene planes parallel to each other. Preferably, the thin film is a continuous length film having a length of 5 cm or more and a width of 1 cm or more, and the thin film is produced by a roll-to-roll method.

Preferably, the thin film of HA or HA / graphene mixture or the graphite film obtained from it has a physical density greater than 1.6 g / cm3 and / / when measured alone (as a free-standing layer in the absence of metal foil). Alternatively, it has a tensile strength greater than 30 MPa. More preferably, the thin film or the graphite film obtained from it has a physical density greater than 1.8 g / cm3 and / or a tensile strength greater than 50 MPa when measured alone. Most preferably, the thin film or the graphite film obtained from it has a physical density greater than 2.0 g / cm3 and / or a tensile strength greater than 80 MPa when measured alone.

The present invention also provides a rechargeable lithium battery or a lithium ion battery containing the current collector of the present invention as an anode current collector and / or a cathode current collector. The rechargeable lithium battery may be a lithium-sulfur cell, a lithium-sulene cell, a lithium sulfur / selenium cell, a lithium-air cell, a lithium-graphene cell, or a lithium-carbon cell.

The present invention also provides a capacitor containing the current collector of the present invention as an anode current collector or a cathode current collector, the capacitors being a symmetric ultracapacitor, an asymmetric ultracapacitor cell, a hybrid supercapacitor-battery cell, and the like. Alternatively, it is a lithium ion capacitor cell.

The present invention also provides a method for producing a highly oriented humic acid film bonded metal foil current collector for use in batteries or supercapacitors. The method is
(A) In the step of preparing a dispersion of humic acid (HA) or chemically functionalized humic acid (CHA) sheet dispersed in a liquid medium, the HA sheet has an oxygen content higher than 5% by weight. A step that contains or the CHA sheet contains a non-carbon element content greater than 5% by weight, and
(B) In the step of distributing and depositing a HA or CHA dispersion on at least one primary surface of a metal foil to form a wet layer of HA or CHA on the surface, the partitioning and deposition procedure orient-induced stress on the dispersion. And the process including the process to be used for
(C) The liquid medium is partially or completely removed from the wet layer of HA or CHA and dried _{with a hexagonal carbon plane and an interplane spacing d 002 of 0.4 nm to 1.3 nm as measured by X-ray diffraction.} The process of forming the HA or CHA layer and
(D) Fumic acid (d) in the step of heat treating the dried HA or CHA layer at a first heat treatment temperature higher than 80 ° C. for a time sufficient to produce a highly oriented fumic acid film bonded metal foil current collector. The fumic acid) film contains an interconnected, assimilated or heat-reduced HA or CHA sheet that is substantially parallel to each other and chemically bonded and parallel to the primary surface, with 1.3 g / g of fumic acid film. Includes steps having a physical density of cm ³ or greater, a thermal conductivity of at least 250 W / mK, and / or an electrical conductivity of 500 S / cm or greater. The method may further include the step of compressing the assimilated or reduced HA or CHA humic acid film after the step (d).

The method further comprises the additional step (e) for a time sufficient to produce the graphite film bonded metal foil current collector, the fumic acid film bonded metal foil is further subjected to a second heat treatment temperature higher than the first heat treatment temperature. In the heat treatment step, the graphite film has an interplanetary spacing d _{002 of} less than 0.4 nm and an oxygen content or non-carbon element content of less than 5% by weight, and (f) the graphite film is compressed to 1.3 g. It may include the step of producing a highly conductive graphite film having a physical density of / cm ³ or more, a thermal conductivity of at least 500 W / mK, and / or an electrical conductivity of 1,000 S / cm or more. The highly conductive graphite film preferably has a thickness of 5 nm to 20 μm, but more preferably 10 nm to 2 μm.

The HA or CHA dispersion may further contain a graphene sheet or molecule dispersed therein, the ratio of HA to graphene or CHA to graphene is 1/100 to 100/1, where graphene is pure graphene. , Graphene oxide, reduced graphene oxide, graphene fluoride, graphene bromide, graphene iodide, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, or a combination thereof. Method, for a time sufficient to produce a graphite film having an additional step (e) the oxygen content of the spacing d ₀₀₂ and less than 5 wt% between the faces of less than 0.4nm or non-carbon element content, A step of further heat-treating the assimilated or reduced HA or CHA fumic acid film at a second heat treatment temperature higher than the first heat treatment temperature, and step (f) compressing the graphite film to 1.6 g / cm ³ or more. It may include a step of producing a highly conductive graphite film having a physical density, a thermal conductivity of at least 700 W / mK, and / or an electrical conductivity of 1,500 S / cm or more.

In certain embodiments, the HA or CHA sheet is in sufficient quantity to form a liquid crystal phase in the liquid medium. Preferably, the dispersion contains a first volume fraction of HA or CHA dispersed in a liquid medium that exceeds _{the critical volume fraction (V c} ) for the formation of the liquid crystal phase, and the dispersion is enriched. The second volume fraction of HA or CHA, which is larger than the first volume fraction, is reached to improve the orientation of the HA or CHA sheet. Preferably, the first volume fraction is equal to a weight fraction of 0.05% to 3.0% by weight of HA or CHA in the dispersion. The dispersion may be concentrated prior to step (b) to contain more than 3.0% by weight and less than 15% by weight of HA or CHA dispersed in the liquid medium.

In some embodiments, the dispersion further contains a polymer that is dissolved in the liquid medium or adhered to HA or CHA.

CHA is polymer, SO ₃ H, COOH, NH ₂ , OH, R'CHOH, CHO, CN, COCl, aryl, COSH, SH, COOR', SR', SiR' ₃ , Si (-OR' --- _{) y R '3 -y, Si} (- O - SiR' 2 -) oR ', R'', Li, AlR' 2, Hg - X, TlZ 2 and Mg - X (wherein y Is an integer less than or equal to 3, R'is hydrogen, alkyl, aryl, cycloalkyl, or aralkyl, cycloaryl, or poly (alkyl ether), and R'is fluoroalkyl, fluoroaryl, fluorocycloalkyl, fluoro. It may contain a chemical functional group selected from (where X is an arylide and Z is a carboxylate or trifluoroacetate, or a combination thereof), which is aralkyl or cycloaryl.

Graphene sheets, if present, polymer, SO ₃ H, COOH, NH ₂ , OH, R'CHOH, CHO, CN, COCl, aryl, COSH, SH, COOR', SR', SiR' ₃ , Si _{(--OR '-) y R'} 3 -y, Si (- O - SiR '2 -) oR', R '', Li, AlR '2, Hg - X, TlZ 2 and Mg --X (y is an integer less than or equal to 3 in the formula, R'is hydrogen, alkyl, aryl, cycloalkyl, or aralkyl, cycloaryl, or poly (alkyl ether), and R'' is fluoroalkyl, fluoro. Aryl, fluorocycloalkyl, fluoroaralkyl or cycloaryl, where X is halide and Z is carboxylate or trifluoroacetate, or a combination thereof), chemically functional with a chemical functional group selected from them. It may contain a modified graphene.

Preferably, the liquid medium consists of water or a mixture of water and alcohol. Alternatively, the liquid medium is a non-aqueous solvent selected from polyethylene glycol, ethylene glycol, propylene glycol, alcohol, sugar alcohol, polyglycerol, glycol ether, amine solvent, amide solvent, alkylene carbonate, organic acid, or inorganic acid. Contains.

The second heat treatment temperature is _{sufficient time to reduce the interplanar spacing d 002} to a value of less than 0.36 nm and to reduce the oxygen or non-carbon element content to less than 0.1% by weight. May be higher than 1,500 ° C. Specifically, the second heat treatment temperature may be 1,500 ° C. to 3,200 ° C.

The method is preferably a roll-to-roll or reel-to-reel method, wherein step (b) is a step of feeding a sheet of metal foil from the rollers to the deposition area and a metal layer of HA or CHA dispersion. The steps of depositing on at least one primary surface of the foil to form a wet layer of HA or CHA dispersion on it, and drying the HA or CHA dispersion and depositing on the surface of the metal foil were dried. It includes a step of forming the HA or CHA layer and a step of collecting the HA or CHA layer deposited metal foil on a collector roller.

In certain embodiments, the first heat treatment temperature comprises a temperature in the range of 100 ° C. to 1,500 ° C., and the highly oriented humic acid film has an oxygen content of less than 2.0% and a face-to-face spacing of less than 0.35 nm. It has an interval, ^{a physical density of 1.6 g / cm 3} or more, a thermal conductivity of at least 800 W / mK, and / or an electrical conductivity of 2,500 S / cm or more. In another embodiment, the first heat treatment temperature comprises a temperature in the range of 1,500 ° C to 2,100 ° C, resulting in a highly conductive graphite film, the highly oriented humic acid film having less than 1.0% oxygen. It has a content, an inter-plane spacing of less than 0.345 nm, a thermal conductivity of at least 1,000 W / mK, and / or an electrical conductivity of 5,000 S / cm or more.

In some embodiments, the first and / or second heat treatment temperature comprises a temperature above 2,100 ° C. and the highly conductive graphite film has an oxygen content of 0.1% or less, less than 0.340 nm. Graphene spacing, mosaic spread value of 0.7 or less, thermal conductivity of at least 1,300 W / mK, and / or electrical conductivity of 8,000 S / cm or more. When the second heat treatment temperature includes a temperature of 2,500 ° C. or higher, the highly conductive graphite film has a graphene spacing of less than 0.336 nm, a mosaic spread value of 0.4 or less, and a heat greater than 1,500 W / mK. It has conductivity and / or electrical conductivity greater than 10,000 S / cm. The degree of graphitization may be 80% or more, and the mosaic spread value may be less than 0.4.

Typically, the HA or CHA sheet has a maximum original length and the highly oriented humic acid film contains an HA or CHA sheet having a length greater than the maximum original length. This means that one humic acid molecule assimilates with another HA molecule in an edge-to-edge manner to increase the length or width of a planar molecule or sheet. The heat treatment step (e) includes the step of chemically linking, assimilating, or chemically bonding the HA or CHA sheet with another HA or CHA sheet or with the graphene sheet to form a graphite structure. The highly conductive graphite film is a polycrystalline graphene structure having a preferable crystal orientation at the time of measurement by the X-ray diffraction method.

The method typically has an electrical conductivity greater than 5,000 S / cm, a thermal conductivity greater than 800 W / mK, a physical density greater than 1.9 g / cm3, a tensile strength greater than 80 MPa, and / or greater than 60 GPa. It results in the formation of a highly oriented graphite film with elastic modulus. More typically, highly oriented graphite films have an elastic modulus greater than 8,000 S / cm, a thermal conductivity greater than 1,200 W / mK, a physical density greater than 2.0 g / cm3, and a tensile strength greater than 100 MPa. And / or have an elastic modulus greater than 80 GPa. Due to the final heat conductivity (first or second heat treatment temperature) above 1,500 ° C., the highly oriented graphite film has an electrical conductivity greater than 12,000 S / cm, a thermal conductivity greater than 1,500 W / mK, 2 It has a physical density greater than 1 g / cm3, a tensile strength greater than 120 MPa, and / or an elasticity greater than 120 GPa.

FIG. 1A is a flow chart illustrating various prior art methods for producing exfoliated graphite products (flexible graphite foil and flexible graphite composites) and pyrolyzed graphite (lower portion). FIG. 1B is a method for producing an aggregate of isolated graphene sheets and graphene or graphene oxide sheets in the form of graphene paper or membrane. FIG. 1C is a method for producing an aggregate of isolated graphene sheets and graphene or graphene oxide sheets in the form of graphene paper or membrane. FIG. 2 is an SEM image of a cross section of a flexible graphite foil showing many graphite flakes with orientations that are not parallel to the surface of the flexible graphite foil and also showing many defects, kinked or broken flakes. Is. FIG. 3 (A) is an SEM image of HA liquid crystal-derived HOGF, where the plurality of hexagonal carbon planes are seamlessly assimilated into a continuous length graphene-like sheet or layer that can be tens of centimeters wide or tens of centimeters long. (Only 50 μm wide of HOGF with a width of 10 cm is shown in this SEM image). FIG. 3B is an SEM image of a cross section of conventional graphene paper made from discrete reduced graphene oxide sheets / platelits using a papermaking process (eg, vacuum auxiliary filtration). The image shows many discrete graphene sheets that are folded or interrupted (unintegrated), the orientation is not parallel to the film / paper surface, and there are many defects or imperfections. FIG. 3C is a schematic representation of a film of highly oriented humic acid molecules that are chemically assimilated together to form a highly ordered and conductive graphite film. FIG. 4A shows the thermal conductivity values of HA / GO-derived HOGF, GO-derived HOGF, HA-derived HOGF, and FG foil plotted as a function of the final heat treatment temperature. FIG. 4B is the thermal conductivity values of HA / GO-derived HOGF, HA-derived HOGF, and polyimide-derived HOPG, all plotted as a function of the final HTT. FIG. 4C shows the electrical conductivity values of HA / GO-derived HOGF, GO-derived HOGF, HA-derived HOGF, and FG foil plotted as a function of the final heat treatment temperature. FIG. 5 (A) shows the interplanetary spacing of HA-derived HOGF measured by X-ray diffraction. FIG. 5 (B) shows the oxygen content in HA-derived HOGF. FIG. 5C shows the correlation between graphene spacing and oxygen content. FIG. 5D shows the thermal conductivity values of HA / GO-derived HOGF, GO-derived HOGF, HA-derived HOGF, and FG foil plotted as a function of the final heat treatment temperature. FIG. 6 is the thermal conductivity of the HOGF sample plotted as a function of the ratio of GO sheets in the HA / GO suspension. FIG. 7 (A) shows the tensile strength values of HA / GO-derived HOGF, GO-derived HOGF, HA-derived HOGF, flexible graphite foil, and reduced graphene oxide paper, all plotted as a function of the final heat treatment temperature. Is. FIG. 7B is the tensile modulus of HA / GO-derived HOGF, GO-derived HOGF, and HA-derived HOGF plotted as a function of the final heat treatment temperature. FIG. 8 shows three HA-derived high-orientation films, that is, a high-orientation film obtained by heat-treating an HA film peeled from the glass surface, and a high-orientation film deposited and bonded to the Ti surface during the heat treatment. The thermal conductivity of the film and the highly oriented film deposited and bonded to the Cu foil surface during the heat treatment. FIG. 9A is a discharge capacity value of each of the three Li-S cells as a function of the number of charge / discharge cycles. First cell having HA-bonded Cu foil and HA-bonded Al foil as anode current collector and cathode current collector, respectively; GO / resin coated Cu foil and GO coating as anode current collector and cathode current collector Second cell with Al foil (without pre-etching) (cell of prior art); third cell with Cu foil anode current collector and Al foil cathode current collector (cell of prior art). FIG. 9B is a Ragon plot of three cells. First cell having HA-bonded Cu foil and HA-bonded Al foil as anode current collector and cathode current collector, respectively, coated with GO / resin-coated Cu foil and GO as anode current collector and cathode current collector A second cell (priority cell) having the Al foil (without pre-etching), a third cell having a Cu foil anode current collector and an Al foil cathode current collector (priority cell), respectively. FIG. 10 shows cell capacity values of the three magnesium metal cells. First cell having HA-bonded Cu foil and HA-bonded Al foil as anode current collector and cathode current collector, respectively, coated with GO / resin-coated Cu foil and GO as anode current collector and cathode current collector A second cell (priority cell) having the Al foil (without pre-etching), a third cell having a Cu foil anode current collector and an Al foil cathode current collector (priority cell), respectively.

The present invention provides a humic acid-bonded metal foil thin film collector for use in a battery or supercapacitor (eg, as illustrated graphically in FIG. 1C). In a preferred embodiment, the current collector is (a) with a free-standing, unsupported thin metal foil having a thickness of 1 μm to 30 μm and two opposed, substantially parallel primary surfaces (214 in FIG. 1 (C)). , (B) include a thin film 212 of humic acid (HA) or HA / graphene mixture chemically bonded to at least one of the two opposing primary surfaces (without the use of binders or adhesives). FIG. 1C simply shows that one primary surface of the metal foil 214 is bonded with a thin film 212 of HA or HA / graphene mixture. However, preferably, the primary surface on the opposite side is also bonded with a thin film of HA or HA / graphene mixture (not shown in FIG. 1 (C)). As electrode terminals for electrically connecting the battery / supercapacitor to an external circuit, the metal tab 218 is typically welded or soldered to the metal foil 214.

As illustrated in FIG. 1 (C), a preferred embodiment of the present invention is an HA-bonded metal foil current collector, in which the binder resin layer or passivated aluminum oxide layer is HA or HA / graphene mixture Cu. Not present between foil or Al foil. In contrast, as illustrated graphically in FIG. 1B, prior art graphene-coated metal foil collectors typically and always have a graphene layer (graphene-resin composite) and metal foil. A binder resin layer is required between (for example, Cu foil). In the case of the prior art graphene-coated Al foil [Prabaka et al .; Reference 2], the immobilized aluminum oxide (alumina) layer naturally exists between the graphene layer and the Al metal foil. This is due to the known fact that aluminum foil always forms a passivated aluminum oxide layer on the surface of the Al foil during production and exposure to indoor air. Simple cleaning with acetone or alcohol cannot remove this alumina layer. As explained in a later paragraph, the presence of a layer of binder resin or aluminum oxide, even as thin as 1 nm, has a tremendous effect on increasing the contact resistance between the graphene layer and the metal foil. Have. This amazing discovery by us has been totally overlooked by all prior art researchers, so prior art graphene-coated metal foil meets the performance and price requirements of lithium batteries or supercapacitor collectors. Not.

A very significant and unexpected advantage of bringing the humic acid sheet into direct contact with the primary surface of Cu, Ni, steel or Ti foil is without the use of external resin binders or adhesives (thus contact resistance is dramatic). The concept is that HA molecules can be sufficiently bonded to these metal foils under the processing conditions of the present invention. These processing conditions include a step of fully aligning HA (or a mixture of HA and graphene) molecules or sheets on the surface of the metal foil, followed by a two-layer structure in the range of 80 ° C to 1,500 ° C ( A step of heat treatment at a temperature (more typically and preferably in the range of 80 ° C. to 500 ° C., and most typically and preferably in the range of 80 ° C. to 200 ° C.) is included. By optional option, the heat treatment temperature can be as high as 1,500-3,000 ° C. (provided the metal foil can withstand such high temperatures), although not preferred.

These processing conditions include, in the case of an aluminum foil-based current collector, preferably a step of chemically etching and removing the passivated aluminum oxide layer before being coated with HA and joined. The step of heat-treating under the same temperature conditions as described above is included. Alternatively, the HA molecule may be prepared in an acidic state, it has a high oxygen content, exhibits high amounts of -OH and -COOH groups, and has a pH value of less than 5.0 (preferably <3.0 and. Even more preferably, it is characterized by having <2.0). The Al foil may be immersed in a bath of HA solution, where the acidic environment will passivate the Al ₂ O ₃ layer naturally. When the Al foil emerges from the bath, HA molecules or sheets naturally adhere to the clean, etched Al foil surface, effectively preventing exposure of the Al foil surface to open air (and thus immobilization Al ₂ O). _{There are no three} layers and there is no additional contact resistance between the Al foil surface and the HA layer). This method has never been disclosed or proposed.

In addition to the chemical bonding power of the HA layer and the chemical etching power of the HA solution of the present invention, the obtained thin film of HA or HA / graphene mixture in the HA bonded metal foil of the present invention has a thickness of 10 nm to 10 μm. All HA and graphene have an oxygen content of 0.1% to 10% by weight, an interplanetary spacing of 0.335 to 0.50 nm, and ^{a physical density of 1.3 to 2.2 g / cm 3.} Thermal conductivity greater than 500 W / mK and / or 1,500 S / cm when the sheets (if present) are oriented substantially parallel to each other and parallel to the primary surface and measured alone without thin metal foil. Shows greater electrical conductivity. This thin film of HA or HA / graphene is chemically inert and provides a highly effective protective layer against corrosion of the underlying metal foil.

Here, the magnitude of the total resistance (including contact resistance) of the three-layer structure as shown in FIG. 1 (B) will be examined in more detail. Electrons in the graphene layer 202 (layer 1) move around in this layer, traverse the binder resin or passivated alumina layer 206 (layer 2), and then in the metal foil layer 204 (layer 3) terminal tabs 208. Must move towards. For brevity, only the thickness of the graphene layer, the thickness of the binder / passivation layer, and the total resistance to electrons moving across the thickness of the metal foil layer are considered. The movement of electrons in the in-plane direction of both graphene or metal foil is rapid and low resistance, so this resistance is ignored in familiar calculations.

The resistivity in the thickness direction of the sheet / film of the conductor is given by R = (1 / σ) (t / A), and in the formula, A = cross section (length x width) of the conductor, t = thickness of the conductor. Then, σ = conductivity = 1 / ρ, and ρ = resistivity, material constant. A graphene-coated current collector containing a binder or passivation metal oxide layer has a graphene film, a passivation resin layer (or passivation alumina layer), and a metal foil layer electrically connected in series. It may be regarded as a three-layer structure (FIG. 1 (B)).

The total resistance is the sum of the resistance values of the three layers: R = R ₁ + R ₂ + R ₃ = ρ ₁ (t ₁ / A ₁ ) + ρ ₂ (t ₂ / A ₂ ) + ρ ₃ (t ₃ / A ₃ ) = (1 / σ ₁ ) (t ₁ / A ₁ ) + (1 / σ ₂ ) (t ₂ / A ₂ ) + (1 / σ ₃ ) (t ₃ / A ₃ ), in the equation, ρ = resistance , Σ = conductivity, t = thickness, and A = layer area, and roughly A ₁ = A ₂ = A ₃ . Scanning electron microscopy shows that the binder resin or passivated alumina layer is typically 5-100 nm thick. The resistivity of the most commonly used binder resin (PVDF) and the resistivity of alumina (Al ₂ O ₃ ) are typically in ^{the range of 10 13} to ¹⁵ ohm-cm. Considering A ₁ = A ₂ = A ₃ = 1 cm ² , the resistivity in the thickness direction of the graphene layer ρ ₁ = 0.1 ohm-cm, the resistivity of the binder or the alumina layer ρ ₂ = 1 × 10 ¹⁴ ohm- The resistivity of cm and the metal foil layer is ρ ₃ = 1.7 × 10 ^-6 ohm-cm (Cu foil) or ρ ₃ = 2.7 × 10 ^-6 ohm-cm (Al foil). Further, consider the optimum conditions in which the thickness of the Cu or Al foil is 6 μm, the thickness of the graphene layer is 1 μm, and the thickness of the binder resin layer is only 0.5 nm (actually, it is 5 nm to 100 nm). .. In that case, the total resistance of the three-layer structure is 5 × 10 ⁶ ohms and the total conductivity is ^{only 1.4 × 10 -10} S / cm (see the first row of data in Table 1 below). reference). When the binder resin layer is considered to be a thickness of 10 nm, the total resistance of the three-layer structure is 1 × ¹⁰ 8 ohm, Zenshirubedenritsu is only 7.0 × ¹⁰ -12 S / cm (the table below See the 4th row of data in 1). Such a three-layer composite structure is not a good collector for batteries or supercapacitors, as high internal resistance means low output voltage and high amounts of internal heat generated. Similar results were observed for current collectors based on Ni, Ti, and stainless steel foils (lines 7-10 of the data in Table 1).

In contrast, in the absence of the binder resin or alumina layer (t ₂ = 0), as in the case of the current collector of the present invention, the total resistance of the graphene oxide-bonded Cu foil is (1 μm of the binder resin layer). It has a value of ^{1.0 × 10 -5} ohms (for 1.0 × 10 ^{+ 7} ohms) of the contained three-layer structure. See Table 2 below. This represents a 12 digit difference (not 12 times)! ^{The conductivity is 7.0 x 10 + 1} S / cm for the two-layer structure, as opposed to ^{7.0 x 10-11} S / cm for the corresponding three-layer structure. The difference is 12 digits. Further, the lithium battery and supercapacitor characterized by the graphene oxide-bonded metal foil current collector of the present invention have a higher voltage output, without loss of capacity or corrosion problems when compared to the graphene-based current collector of the prior art. We have found that it always exhibits higher energy density, higher output density, more stable charge-discharge cycle response, and lasts longer.

In the following, a description of humic acid and graphene, which are the two main components in the thin film coated on the metal foil, will be described.

In bulk natural flake graphite, each grain is composed of a plurality of crystal grains (crystal grains are graphite single crystals or microcrystals), and the grain boundaries (amorphous or defective regions) are of adjacent graphite single crystals. It is a three-dimensional graphite material that defines boundaries. Each crystal grain is composed of a plurality of graphene planes oriented parallel to each other. The graphene plane in a graphite crystallite is composed of two-dimensional carbon atoms that occupy a hexagonal lattice. In a given grain or single crystal, the graphene planes are stacked and joined by van der Waals forces in the c-direction crystal orientation (perpendicular to the graphene plane or base plane). All graphene planes of one crystal grain are parallel to each other, but typically the graphene planes of one crystal grain and the graphene planes of adjacent crystal grains have different orientations. In other words, the orientation of the various grains of graphite particles typically varies from grain to grain.

The graphite single crystal (microcrystal) itself is anisotropic, and the properties measured along the direction of the base plane (a-axis or b-axis crystal direction) are measured along the c-axis crystal direction (thickness direction). It is dramatically different from what was done. For example, the thermal conductivity of a graphite single crystal can be up to about 1,920 W / mK (theoretical value) or up to 1,800 W / mK (experimental value) on the substrate plane (a-axis and b-axis crystal directions). The thermal conductivity along the c-axis crystal direction is less than 10 W / mK (typically less than 5 W / mK). Moreover, the plurality of crystal grains or microcrystals of graphite particles are typically all oriented in different directions. Therefore, natural graphite particles composed of multiple crystal grains with different orientations exhibit average properties between these two extrema (ie typically <100 W / mK).

If the interfaceted van der Waals force can be overcome, the constituent graphene surfaces (typically width / length 30 nm to 2 μm) of the graphite microcrystals are stripped and extracted or isolated from the graphite microcrystals of carbon atoms. A single graphene sheet can be obtained. An isolated, single-layer graphene sheet of hexagonal carbon atoms is commonly referred to as single-layer graphene. A laminate of a plurality of graphene surfaces joined by a van der Waals force in the thickness direction at an interval of 0.3354 nm between graphene surfaces is generally referred to as a multi-layer graphene. Multi-layer graphene plate lits have up to 300 layers of graphene surfaces (thickness <100 nm), more typically up to 30 graphene surfaces (thickness <10 nm), and even more typically up to 20 graphene surfaces. It has a graphene surface (thickness <7 nm), and most typically up to 10 (commonly referred to in the scientific community as multi-layer graphene). Single-layer graphene and multi-layer graphene sheets are collectively referred to as "nanographene platelits" (NGPs). Graphene sheets / platelits or NGPs are a novel class of carbon nanomaterials (two-dimensional nanocarbons) that are clearly distinguished from zero-dimensional fullerenes, one-dimensional CNTs, and three-dimensional graphite.

Our research group began developing pure graphene materials, isolated graphene oxide sheets, and related manufacturing processes as early as 2002: (1) B. Z. Jang and W. C. Huang, "Nano-scaled Graphene Plates", US Pat. No. 7,071,258 (07/04/2006), application filed October 21, 2002; (2) B. Z. Jang, et al. “Process for Producing Nano-scaled Graphene Plates”, US Patent Application No. 10 / 858,814 (06/03/2004); and (3) B.I. Z. Jang, A. Zhamu, and J. et al. Guo, “Process for Producing Nano-scaled Platelets and Nanocomposites”, US Patent Application No. 11/509,424 (08/25/2006). Historically, Brodie first demonstrated the synthesis of graphite oxide in 1859 by adding an amount of potassium chlorate to a slurry of graphite in fuming nitric acid. In 1898, Studionier refined this procedure by using concentrated sulfuric acid and fuming nitric acid and adding chlorate in multiple aliquots during the reaction. This small change in procedure has made the production of highly oxidized graphite in a single reactor significantly more practical. In 1958, Hummers reported on the most commonly used methods today. Graphite, it is oxidized by treatment with KMnO ₄ and NaNO ₃ of concentrated _H in 2 SO _4. However, these previous studies failed to isolate and identify completely exfoliated and isolated graphene oxide sheets. Also, these studies could not disclose the isolation of pure, unoxidized single-layer or multi-layer graphene sheets.

In practice (eg, as illustrated in FIG. 1 (A)), NGP typically intercalates natural graphite particles 100 with a strong acid and / or oxidant to the graphite interlayer compound 102 (GIC) or Obtained by obtaining graphite oxide (GO). The presence of species or functional groups in the interstitial lattice space between graphene planes _{helps to increase the inter-graphene spacing (d 002} , measured by X-ray diffraction), thereby otherwise c-axis the graphene planes. Significantly reduces the van der Waals force held along. GIC or GO is very often produced by immersing natural graphite powder in a mixture of sulfuric acid, nitric acid (oxidizer), and another oxidant (eg potassium permanganate or sodium perchlorate). The resulting GIC (102) is actually some type of graphite oxide (GO) particles. The GIC or GO is then repeatedly washed and rinsed in water to remove excess acid, resulting in a graphite oxide suspension or dispersion, which is dispersed in water and dispersed and visually. Contains identifiable graphite oxide particles. There are two processing paths that follow this rinsing process:

Path 1 requires the step of removing water from the suspension to obtain "expandable graphite", which is essentially a mass of dried GIC or dried graphite oxide particles. When expansive graphite is exposed to temperatures typically in the range of 800 to 1,050 ° C. for about 30 seconds to 2 minutes, the GIC undergoes 30 to 300 times rapid volume expansion and is a "graphite worm" (104). They are a collection of exfoliated, but barely separated, graphite flakes that remain interconnected, respectively.

In path 1, these graphite worms (exfoliated graphite or "mesh structure of interconnected / unseparated graphite flakes") are recompressed in the range of 0.1 mm (100 μm) to 0.5 mm (500 μm). Flexible graphite sheets or foils (106) can be obtained that typically have a thickness of. Instead, use a low-strength air mill or shear for the purpose of producing so-called "expanded graphite flakes" (108) containing primarily graphite flakes or plate lits (thus not nanomaterials by definition) thicker than 100 nm. You may choose to use it to simply break the graphite worm. These expanded graphite flakes may be produced on a paper-like graphite mat (110).

Exfoliated graphite worms, expanded graphite flakes, as well as recompressed lumps of graphite worms (commonly referred to as flexible graphite sheets or flexible graphite foils) are all one-dimensional nanocarbon materials (CNT or CNF) or It is a three-dimensional graphite material that is fundamentally different from any of the two-dimensional nanocarbon materials (graphene sheet or plate lit, NGP) and can be clearly distinguished. Flexible graphite (FG) foils can be used as heat spreader materials, but typically have a maximum in-plane thermal conductivity of less than 500 W / mK (more typically <300 W / mK) and a surface of 1,500 S / cm or less. Indicates the internal electrical conductivity. These low conductivity values are a direct result of many defects, wrinkled or broken graphite flakes, interruptions or gaps between graphite flakes, and non-parallel flakes (eg, the SEM image of FIG. 2). Many flakes are tilted relative to each other at very large angles (eg, 20-40 degrees orientation difference).

In path 1B, the exfoliated graphite is subjected to high-strength mechanical shearing (eg, using an ultrasonicator, high-strength mixer, high-strength air jet mill, or high-energy ball mill) and our US Patent Application No. 10/858 , 814 to form separate single-layer and multi-layer graphene sheets (collectively referred to as NGP, 112). Single-layer graphene can be only 0.34 nm, while multi-layer graphene can have thicknesses up to 100 nm, but more typically less than 20 nm. In that case, the graphene sheet or plate lit may be manufactured on graphene paper or membrane (114).

Path 2 requires sonication of the graphite oxide suspension for the purpose of separating / isolating the graphene oxide sheet alone from the graphite oxide particles. This is because the graphene interplanetary separation has increased from 0.3354 nm for natural graphite to 0.6-1.1 nm for highly oxidized graphite oxide, providing a van der Waals force that holds adjacent surfaces together. It is based on the idea of significantly weakening. The ultrasonic power may be sufficient to further separate the graphene surface sheet to form a separated, isolated, or discrete graphene oxide (GO) sheet. These graphene oxide sheets are then chemically or thermally reduced to 0.001% to 10% by weight, more typically 0.01% to 5% by weight, most typically and preferably 2. It is possible to obtain "reduced graphene oxide" (RGO), which typically has an oxygen content of less than% by weight.

For the purposes of defining the claims of the present application, NGP includes discrete sheets / plates of single-layer and multi-layer pure graphene, graphene oxide, or reduced graphene oxide (RGO). Pure graphene has essentially 0% oxygen. The RGO typically has an oxygen content of 0.001% to 5% by weight. Graphene oxide (including RGO) can have 0.001% to 50% by weight oxygen.

For thermal management applications of electronic devices (eg as heat sink material), it has been pointed out that flexible graphite foil (obtained by compressing or roll pressing a stripped graphite worm) has the following major defects: May be: (1) As shown above, flexible graphite (FG) foils have a relatively low thermal conductivity, typically <500 W / mK and more typically <300 W / mK. Is shown. By impregnating the exfoliated graphite with a resin, the resulting composite exhibits even lower thermal conductivity (typically << 200 W / mK, more typically <100 W / mK). (2) The flexible graphite foil without the resin impregnated in or coated on it has low strength, low stiffness and poor structural integrity. The high tendency of flexible graphite foils to fall apart makes them difficult to handle in the process of manufacturing heat sinks. In fact, flexible graphite sheets (typically 50-200 μm thick) are so “flexible” that they are sufficient to produce fin component materials for heat sinks with fins. Not hard. (3) A very subtle, generally neglected or overlooked but crucial feature of FG foils is that they become flaky and graphite flakes easily fall off the surface of the FG sheet and other parts of the microelectronic device. It has a high tendency to be released into graphite. These highly electrically conductive flakes (typically 1-200 μm in lateral dimensions and> 100 nm in thickness) can cause internal short circuits and failures of electronic devices.

Similarly, when solid NGP (including discrete sheets / plate lits of pure graphene, GO, and RGO) is filled into a non-woven aggregate film, membrane, or paper sheet (114) using a papermaking method. Unless these sheets / plate lits are tightly packed and the film / membrane / paper is very thin (eg <1 μm, it is mechanically weak), they typically do not exhibit high thermal conductivity. This is described in our previous US Patent Application No. 11 / 784,606 (April 9, 2007). However, it is difficult to mass-produce an ultra-thin film or a paper sheet (<10 μm), and it is difficult to handle when these thin films are to be mixed as a heat sink material. In general, paper structures or mats made from graphene, GO, or RGO plate lits (eg, those paper sheets made by the vacuum auxiliary filtration process) have many defects, wrinkles, or Shows broken graphene sheets, interruptions or gaps between plate lits, and non-parallel plate lits (eg, SEM image of FIG. 3B), showing relatively inadequate thermal conductivity, low electrical conductivity and low structural strength. Bring. These papers or aggregates of discrete NGP, GO or RGO plate lit only (without resin binder) also tend to be flaky, releasing conductive particles into the air.

Another prior art graphite material is a pyrolyzed graphite film, typically thinner than 100 μm. The method begins with carbonizing a polymer film (eg, polyimide) at a carbonization temperature of 400-500 ° C. under typical pressures of 10-15 kg / cm ^{2 for 10-36 hours to obtain a carbonized material.} Then, it is subjected to a graphitization treatment at 2500 to 3,200 ° C. under an ultrahigh pressure of 100 to 300 kg / cm ^{2 for 1 to 24 hours to form a graphite film.} It is technically extremely difficult to maintain such an ultra-high pressure at such an ultra-high temperature. This is a difficult, slow, lengthy, energy-intensive and extremely costly method. Furthermore, it has been difficult to produce a pyrolysis graphite film thinner than 10 μm or thicker than 100 μm from a polymer such as polyimide. This thickness-related problem forms in ultra-thin (<10 μm) and thick films (> 100 μm) while further maintaining the acceptable degree of orientation and mechanical strength of the acceptable polymer chains required for proper carbonization and graphitization. Due to those difficulties in doing so, this class of material comes with it.

The second type of pyrolyzed graphite is produced by a step of decomposing a hydrocarbon gas at high temperature in vacuum, followed by a step of depositing carbon atoms on the surface of a substrate. This vapor phase condensation of cracked hydrocarbons is essentially a chemical vapor deposition (CVD) process. In particular, highly oriented pyrolytic graphite (HOPG) is a material produced by subjecting CVD deposited pyrolytic carbon to uniaxial pressure at a very high temperature (typically 3,000 to 3,300 ° C.). It is combined and coexisting, long-term mechanical compression and ultra-high temperature thermal mechanical processing in a protective atmosphere, very costly, energy intensive, time consuming, time consuming, and technical. Requires an extremely difficult method. The method requires an ultra-high temperature device (with high vacuum, high pressure, or high compression equipment) that is not only very costly to make but also very costly and difficult to maintain. Even under such extreme processing conditions, the resulting HOPG also has many defects, grain boundaries, and misalignment (adjacent graphene planes are not parallel to each other), resulting in unsatisfactory in-plane properties. .. Typically, the best prepared HOPG sheet or block typically contains many imperfectly aligned grains or crystals and a vast amount of grain boundaries and defects.

Similarly, the most recently reported graphene thin films (<2 nm) prepared by catalytic CVD of hydrocarbon gases (eg C ₂ H _{4) on Ni or Cu surfaces are not single grain crystals, but many.} It is a polycrystalline structure with grain boundaries and defects. When Ni or Cu is the catalyst, the carbon atoms obtained by the decomposition of hydrocarbon gas molecules at 800-1,000 ° C. are deposited on the surface of the Ni or Cu foil and are polycrystalline single layer or several layers. Form a sheet of graphene. Crystal grains are typically much smaller in size than 100 μm and more typically smaller in size than 10 μm. These graphene thin films are optically transparent and electrically conductive, and are intended for applications such as touch screens (which replace indium tin oxide or ITO glass) or semiconductors (which replace silicon, Si). Moreover, the Ni or Cu catalytic CVD method is not suitable for deposition of more than 5 graphene surfaces (typically <2 nm) beyond which the underlying Ni or Cu catalyst can no longer provide any catalytic effect. .. There was no experimental evidence that a CVD graphene layer thicker than 5 nm is possible. Both CVD graphene film and HOPG are very expensive.

The above discussion clearly shows that any prior art method or process for producing graphene and graphite thin films has major defects. Therefore, it is equivalent to or better than graphene in terms of essential properties of the current collector (eg, electrical conductivity, thermal conductivity, contact resistance with metal foil), strength, and the desired compatibility of the battery or supercapacitor with the electrolyte. There is an urgent need to have a good new class of carbon nanomaterials. Also, these materials must be able to be manufactured in a more cost-effective, faster, more scalable, and more environmentally friendly way. Manufacturing processes for such novel carbon nanomaterials reduce the amount of unwanted chemicals (or remove them all together), reduce process time, reduce energy consumption, and are undesirable. It must be necessary to reduce or remove effluent into the drainage channels of chemical species (eg, sulfuric acid) or into the air (eg, SO ₂ and NO _2).

Humic acid (HA) is an organic substance commonly found in soil and can be extracted from soil using a base (eg KOH). HA can also be extracted from a type of coal called leonardite, another highly oxidized form of lignite coal. HA extracted from leonaldite contains a large number of oxygenating groups (eg, carboxyl groups) located around the edges of ^{a molecular center (SP 2 core of hexagonal carbon structure) such as graphene.} This material is a bit like graphene oxide (GO) produced by strong acid oxidation of natural graphite. HA has a typical oxygen content of 5% to 42% by weight (other major elements are carbon, hydrogen, and nitrogen). An example of the molecular structure of humic acid with various components such as quinone, phenol, catechol and sugar moiety is shown in Diagram 1 below (Source: Stevenson FJ "Humus Chemistry: Genesis, Composition, Reactions,""John Willey & Sons, New York 1994).

Non-aqueous solvents for fumic acid include polyethylene glycol, ethylene glycol, propylene glycol, alcohols, sugar alcohols, polyglycerols, glycol ethers, amine solvents, amide solvents, alkylene carbonates, organic acids, or inorganic acids. Is done.

The present invention also has a thickness of 2 nm to 30 μm (more typically and preferably 5 nm to 10 μm, even more typically 10 nm to 2 μm) and 1.3 g / cm ³ or more (2.2 g / cm ^3). Provided are methods for producing highly oriented humic acid films (with or without externally added graphene sheets) and humic acid-derived graphite films having a physical density of up to). This film is chemically bonded to the surface of the metal foil. In certain embodiments, the method is
(A) In the step of preparing a dispersion of humic acid (HA) or chemically functionalized humic acid (CHA) in which the HA or CHA sheet is dispersed in a liquid medium, the HA sheet is higher than 5% by weight. A step that contains an oxygen content or a CHA sheet containing a non-carbon element content greater than 5% by weight. (In certain preferred embodiments, the HA or CHA dispersion further comprises a graphene sheet or molecule dispersed therein, the HA to graphene or CHA to graphene ratio being 1/100 to 100/1. Graphene sheets are pure graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene bromide, graphene iodide, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, or a combination thereof. May be selected from.)
(B) In the step of partitioning and depositing the HA or CHA dispersion on at least one primary surface of the metal foil (eg Cu foil) to form a wet layer of HA or CHA, the partitioning and deposition procedure orients the dispersion. The process of subjecting to induced stress. This orientation control stress (typically including shear stress) is such that the HA / CHA sheet (or sheet-like molecule) and graphene sheet (if present) are in the plane direction of the metal foil substrate surface (eg Cu foil). Allows alignment along. Proper alignment of HA / CHA and graphene sheets is between two or more HA / CHA sheets during subsequent heat treatment, or between HA / CHA sheets and graphene sheets. Essential for chemical linkage or assimilation between)
(C) The liquid medium is partially or completely removed from the wet layer of HA or CHA and dried _{with a hexagonal carbon surface and an interplane spacing d 002 of 0.4 nm to 1.3 nm as measured by X-ray diffraction.} 80 for a sufficient amount of time to form a heat-treated HA or CHA layer and (d) a highly oriented fumic acid film containing interconnected or assimilated HA or CHA sheets that are substantially parallel to each other. A step of heat-treating the dried HA or CHA layer at a first heat treatment temperature higher than ° C. is included. Further, the humic acid film is chemically bonded to the surface of the metal foil. Also, these HA / CHA sheets were typically heat reduced. This highly oriented humic acid film of reduced HA or CHA may be subjected to an additional step of compression relative to the metal foil.

The method (with or without the step of compressing) is an additional step (e) _{of a graphite film having a face-to-face spacing of less than 0.4 nm d 002} and an oxygen content or non-carbon element content of less than 5% by weight. A step of further heat-treating the assimilated and reduced HA or CHA humic acid film at a second heat treatment temperature higher than the first heat treatment temperature for a time sufficient to produce, and (f) a graphite film (eg,). A step of producing a highly conductive graphite film bonded to a metal foil by compressing (relative to the Cu foil) can be included.

In an embodiment, step (e) is _{for reducing the face-to-face spacing d 002} to a value between 0.3354 nm and 0.36 nm, and reducing the oxygen or non-carbon content to less than 0.5% by weight. Includes the step of heat treating a highly oriented humic acid film at a second heat treatment temperature (typically> 300 ° C.) that is higher than the first heat treatment temperature for a sufficient amount of time. In a preferred embodiment, the second (or final) heat treatment temperature includes (A) 100-300 ° C, (B) 300-1500 ° C, (C) 1,500-2500 ° C, and / or. (D) Includes at least a temperature selected from 2,500 to 3,200 ° C. Preferably, the second heat treatment temperature includes a temperature in the range of 300 to 1,500 ° C. for at least 1 hour and then a temperature in the range of 1,500 to 3,200 ° C. for at least an additional hour. ..

Typically, when both the first and second heat treatment temperatures are below 1,500 ° C., the highly oriented humic acid (HOHA) film still contains planar molecules that are characteristic of humic acid molecules. Highly oriented humic acid (HOHA) film contains chemically bonded and assimilated hexagonal carbon planes, which are HA / CHA or combined HA / CHA-graphene planes. These planes (hexagonal carbon atoms with a small amount of oxygen-containing groups) are parallel to each other.

This HOHA film typically no longer contains any significant amount of humic acid molecules when exposed to a heat treatment temperature (HTT) of 1,500 ° C. or higher for a sufficient period of time, and essentially all HA. / CHA sheets / molecules were converted to graphene-like or graphene-oxide hexagonal carbon planes parallel to each other. The lateral dimensions (length or width) of these surfaces are very large, typically several times or even orders of magnitude larger than the maximum dimensions (length / width) of the starting HA / CHA sheet. The HOHA of the present invention is essentially a "giant hexagonal carbon crystal" or "giant planar graphene-like layer" in which all constituent graphene-like planes are essentially parallel to each other. This is a unique and new class of material that has not been discovered, developed, or perhaps suggested to exist.

The oriented HA / CHA layer (HOHA film without HTT at> 1,500 ° C.) is itself very unique and novel with a surprisingly large cohesive force (self-bonding, self-polymerization, and self-crosslinking ability). Class material. These properties have not been previously taught or suggested in the prior art.

The above paragraph was written to illustrate the type of current collector obtained by heat treating a HA-bonded or HA / graphene mixture-bonded metal film as a two-layer or three-layer laminate. The HA or HA / graphene layer was not stripped from the metal foil and was heat treated alone (without the metal foil). The obtained current collector does not contain a binder resin or an adhesive. This type is referred to herein as a Type-A current collector. This type of current collector can be heat treated to a maximum temperature close to the melting point of the underlying metal foil. However, certain metal foils (eg Cu, Ti, and steel) appear to be capable of catalyzing chemical connections between HA sheets or between HA and graphene, forming larger HA / graphene domains. It can reduce defects and provide higher thermal and electrical conductivity, as well as structural integrity that would otherwise not be achieved without the use of higher heat treatment temperatures.

The fabrication of Type-B current collectors is described in the following two paragraphs:
Alternatively, the above procedure from (a) to (d) or (e) can be performed by depositing a dispersion of HA or HA / graphene mixture on a plastic film or glass surface to remove the liquid. Occasionally, the resulting dry film is stripped from the plastic film or glass, after which the film is allowed to be heat-treated at any desired temperature. Next, as the self-supporting film, the highly oriented HA film (after heat treatment at a temperature of 80 to 1,500 ° C.) or the obtained graphite film (after heat treatment at a temperature of 1,500 to 3,200 ° C.) is used as a binder resin. Alternatively, it is bonded to one or both of the primary surfaces of a metal foil (eg Cu or Al foil) using an adhesive. Type-A current collectors (where the highly oriented HA film or the highly conductive graphite film obtained from it is a step of depositing a thin film of HA or HA / graphene directly on the surface of the metal foil and without the use of binders. Such a type-B current collector (obtained at equivalent final heat treatment temperature) is the actual liquid electrolyte in the battery or supercapacitor, as compared to (prepared by the step of chemically bonding to this surface). In the environment, it has lower in-plane thermal conductivity, lower in-plane electrical conductivity, higher contact resistance between layers, and lower durability (more easily peeled off).

To partially alleviate these problems, binder materials that are more conductive than typical binder resins (commonly used in the lithium battery and supercapacitor industries, such as PVDF, SBR, etc.) are used. We choose to use. These include intrinsically conductive polymers (eg polyaniline, polypyrrole, polythiophene, etc.), pitches (eg, isotropic pitch, mesophase pitch, etc.), amorphous carbons (eg, by chemical vapor penetration), or carbonized resins. (The current collector is heat-treated after the self-supporting graphite layer is bonded to the metal foil, and the resin binder is converted into a carbon binder in situ).

The following description is for both Type-A and Type-B current collectors.

Step (a) is a significant amount on the edge and / or on the surface of the HA / CHA sheet (eg, having an oxygen content between 20% by weight and 47% by weight, preferably between 30% and 47% by weight). Requires a step of dispersing the HA / CHA sheet or molecule in a liquid medium that can be a mixture of water or water and alcohol for a particular HA or CHA molecule containing −OH and / or −COOH groups. ..

When the volume fraction or weight fraction of HA / CHA exceeds a threshold, the resulting dispersion is found to contain a liquid crystal phase. Preferably, the HA / CHA suspension (dispersion) contains an initial volume fraction of the HA / CHA sheet that exceeds the critical or threshold volume fraction due to the formation of the liquid crystal phase prior to step (b). We have observed that such critical volume fractions are typically equal to the HA / CHA weight fraction in the range of 0.2% to 5.0% by weight of the HA / CHA sheet in the dispersion. However, such a wide range of low HA / CHA content does not make it particularly easy to form the desired thin film using scalable methods such as casting and coating. Since large scale and / or automated casting or coating systems are readily available, it is highly advantageous and desirable to be able to produce thin films by casting or coating, and the method is to produce polymer thin films with consistently high quality. Reliable because of. Therefore, we continued to carry out an in-depth and extensive study of suitability for casting or coating from dispersions containing a liquid crystal phase based on HA / CHA. Larger graphene films by concentrating the dispersion and increasing the HA / CHA content from 0.2% to 5.0% by weight to 4% to 16% by weight of the HA / CHA sheet. We have found that a dispersion is obtained that is very suitable for scale production. Most importantly and quite unexpectedly, the liquid crystal phase is often strengthened rather than simply maintained, making it even easier for the HA / CHA sheet to be oriented along the preferred orientation during the casting or coating procedure. To. In particular, the liquid crystal HA / CHA sheet containing 4% to 16% by weight of the HA / CHA sheet is easily oriented under the influence of shear stress generated by a commonly used casting or coating method. Has the highest tendency.

Therefore, in step (b), the HA / CHA suspension is preferably formed in a thin film layer under the influence of shear stresses that promote laminar flow. An example of such a shearing procedure is to cast or coat a thin film of HA / CHA suspension using a slot die coating machine. This procedure resembles a layer of polymer solution coated on a solid substrate. The rollers, "doctor blades", or wipers create shear stresses when the film is formed or when there is relative motion between the rollers / blades / wipers and the supporting substrate at a sufficiently high relative motion rate. Quite unexpectedly and importantly, such shearing action allows the planar HA / CHA sheets to be well aligned, for example, along the shearing direction. Even more surprising, such molecules when the liquid component in the HA / CHA suspension is subsequently removed to form a fully packed layer of highly aligned HA / CHA sheet that is at least partially dried. The alignment or preferred orientation is not broken. The dried layer has a high birefringence coefficient between the in-plane direction and the direction perpendicular to the plane.

The present invention includes the discovery of a simple amphipathic self-assembly method for producing HA / CHA-based thin films with the desired hexagonal orientation. HA containing 5 to 46% by weight of oxygen may be considered an amphipathic molecule with a negative charge due to its combination of hydrophilic oxygen-containing functional groups and hydrophobic underlying surfaces. Due to CHA, the functional groups can be made hydrophilic or hydrophobic. Better preparation of HA / CHA films with unique hexagonal graphene plane orientation does not require complicated procedures. More precisely, it is achieved by adjusting the synthesis of HA / CHA and manipulating the formation and deformation behavior of the liquid crystal phase to allow self-assembly of HA / CHA sheets in the liquid crystal phase. Will be done.

The HA / CHA suspension was characterized using atomic force microscopy (AFM), Raman spectroscopy, and FTIR to confirm its chemical status. Finally, the presence of the lyotropic liquid crystal (liquid crystal HA phase) of the HA sheet in aqueous solution was demonstrated by observation of cross-polarized light.

Two main aspects to determine if 1-D or 2-D species can form a liquid crystal phase in a liquid medium: aspect ratio (length / width / diameter to thickness ratio) and liquid medium Sufficient dispersibility or solubility of this material in is considered. HA or CHA sheets are characterized by high anisotropy with a single or minor atom thickness (t) and a width, usually on the micrometer scale (w). According to Onsager's theory, high aspect ratio 2D sheets can form liquid crystals in the dispersion when their volume fractions exceed the critical value:
V _c ≒ 4t / w (Equation 1)
Assuming that the graphene-like surface has a thickness of 0.34 nm and a width of 1 μm, the required critical volume is V _c ≈ 4 t / w = 4 × 0.34 / 1,000 = 1.36 × 10 ^-3 = It is 0.136%. However, pure graphene sheets are not soluble in water due to their strong π-π stacking action and _{are approximately 0. 0 in common organic solvents (maximum volume fraction V m} , N-methylpyrrolidone (NMP)). It has a low dispersibility of ^{about 1.5 × 10-5} ) in 7 × ^10-5 and ortho-dichlorobenzene. Fortunately, due to the molecular structure of HA or CHA, due to the large number of oxygen-containing functional groups attached to its edges, to water and polar organic solvents such as alcohol, N, N-dimethylformamide (DMF) and NMP. It can show good dispersibility to. Natural HAs (eg, derived from coal) are also polyethylene glycols, ethylene glycols, propylene glycols, alcohols, sugar alcohols, polyglycerols, glycol ethers, amine solvents, amide solvents, alkylene carbonates, organic acids, inorganic acids, or It is very soluble in non-aqueous solvents for humic acid, such as their mixtures.

According to theoretical predictions, the critical volume fraction of HA / CHA can probably be lower than 0.2% or the critical weight fraction less than 0.3%, but for the HA / CHA sheet to form a liquid crystal. We observed that the critical weight fraction was significantly higher than 0.4% by weight. The most stable liquid crystals are present when the weight fraction of the HA / CHA sheet is in the range of 0.6% to 5.0%, which allows high stability over a wide temperature range. To investigate the effect of HA / CHA size on the formation of its liquid crystal structure, HA / CHA samples were prepared using pH-assisted selective precipitation techniques. The lateral size of the HA / CHA sheet was evaluated by dynamic light scattering (DLS) and by AFM by three different measurement methods.

While investigating the HA / CHA liquid crystal, we made an unexpected but very important finding: the liquid crystal phase of the HA / CHA sheet in water and other solvents is mechanically disturbed (eg mechanical mixing, shearing, turbulence). It can be easily damaged or destroyed by the flow of the liquid crystal display, etc.). When the concentration of the HA / CHA sheet is gradually increased to more than 5% (preferably 5% to 16% by weight) by carefully removing (eg, vaporizing) the liquid medium without mechanically damaging the liquid crystal structure. The mechanical stability of these liquid crystals can be significantly improved. With HA / CHA weight fractions in the range of 5-16%, we further find that HA / CHA sheets are particularly easy to form the desired orientation during casting or coating to form a thin film. Observed.

Thermodynamically, the process of amphipathic HA / CHA self-assembly to the liquid crystal phase is the interaction of enthalpy changes (ΔH) and entropy changes (ΔS) as shown in equation (2): ΔG _{self- assembly} = ΔH _{self-assembly-} TΔS _{self-assembly} (2)
Previous studies of thermodynamic driving forces for amphipathic self-assembly to the liquid crystal phase show that entropy contributions play a dominant role, but enthalpy changes are often undesirable. Onsager's theory predicts that high aspect ratio particles can form a liquid crystal phase that exceeds the critical volume fraction due to the net gain of entropy, as the loss of orientation entropy is compensated for by the increased translational entropy. Specifically, particles with higher aspect ratios promote the formation of long-range liquid crystal phases. Another possible reason for the effect of the HA / CHA aspect ratio may be the structural waviness of the HA / CHA sheet in the solvent, as the restoring force generated by bending the sheet is much weaker than the restoring force along the sheet. It has been found that the degree of HA / CHA wavy morphology in a solvent can be further increased if its aspect ratio is increased. This wavy structure significantly affects both intramolecular and intramolecular interactions of HA / CHA in suspension.

A well-peeled HA / CHA sheet with strong long-range electrostatic repulsion is required to achieve long-range ordering of the aqueous dispersion. Forming a liquid crystal structure from colloidal particles typically requires a delicate balance between long-range repulsive forces such as electrostatic forces and short-range attractive forces such as van der Waals forces and π-π interactions. If the long-range repulsive force is not strong enough to overcome the short-range attractive force, only agglutination of colloidal particles or weak formation of lyotropic liquid crystals with small periodicity will inevitably occur. In HA / CHA aqueous dispersions, the long-range repulsive interaction is provided by the electric double layer formed by the ionized oxygen functional groups. Although the HA / CHA sheet still contains a significant portion of the hydrophobic domain, the π-π attractive interaction and van der Waals forces can be effectively overcome by adjusting the long-range electrostatic repulsion.

The chemical composition of HA / CHA plays an important role in regulating electrostatic interactions in aqueous or organic solvent dispersions. Increasing the surface charge density results in an increase in the strength of the electrostatic repulsive force with respect to the attractive force. The ratio of aromatic and oxygenated domains can be easily adjusted by the level of oxidation or chemical modification of the hexagonal carbon plane. The results of Fourier transform infrared spectroscopy in the HA / CHA Attenuated Total Reflectance Mode (FTIR-ATR) show that oxidized species (hydroxyl, epoxy, and carboxyl groups) are present on the HA / CHA surface. .. Thermogravimetric analysis of nitrogen (TGA) was used to closely examine the density of oxygen functional groups on the HA / CHA surface. For highly oxidized HA, a mass loss of about 28% by weight is found at about 250 ° C., which is attributed to the decomposition of oxygen-containing unstable species. Below 160 ° C., a mass loss of about 16% by weight is observed, which corresponds to the desorption of physically absorbed water. The results of HA X-ray photoelectron spectroscopy (XPS) show that the atomic ratio of C / O is about 1.9. This suggests that HA has a relatively high density of oxygen functional groups. In addition, we also prepared HA containing lower densities of oxygen functional groups by simply varying the time and temperature of thermal or chemical reduction of strongly oxidized HA (eg from Leonardite coal). We have observed that we can preferentially find liquid crystals with oxygen weight fractions in the range of 5% -40%, more preferably 5% -30%, most preferably 5% -20%.

Since the Debye screening length (κ-1) can be effectively increased by reducing the concentration of free ions surrounding the HA sheet, colloidal interactions between HA sheets can be significantly affected by ionic strength. The electrostatic repulsive force of the HA liquid crystal in water can decrease as the salt concentration increases. As a result, more water is expelled from the HA inter-story gap, and the d-spacing is reduced accordingly. Therefore, ionic impurities in the HA dispersion are decisive factors that affect the formation of the HA liquid crystal structure, and therefore should be sufficiently removed.

However, we also introduce HA / CHA dispersions into casting or coating operations by introducing a small amount of polymer (up to 10% by weight, but preferably up to 5% by weight, most preferably up to 2%). We have found that it can help stabilize the liquid crystal phase at times. Appropriate functional groups and concentrations can enhance the GO / CFG orientation of the resulting film. This has also never been taught or suggested in previous publications or patents.

Next, the dried HA / CHA layer may be subjected to heat treatment. A well-programmed heat treatment procedure involves at least two heat treatment temperatures (a first temperature for a period of time, then a second temperature, and then maintained at this second temperature for another period of time). , Or any other combination of at least two heat treatment temperatures (HTTs), including an initial treatment temperature (first temperature) and a final HTT that is higher than the first temperature.

The first heat treatment temperature is for chemical ligation and thermal reduction of HA / CHA and is carried out at a first temperature of> 80 ° C (up to 1,000 ° C, but preferably up to 700 ° C, most preferably 300 ° C. Can be up to ° C). This is referred to herein as Regime 1.
Regime 1 (up to 300 ° C.): In this temperature range (initial chemical linkage and heat reduction regime), compounding, polymerization (edge-to-edge assimilation), and cross-linking between adjacent HA / CHA sheets begin to occur. Multiple HA / CHA sheets are packed side by side and chemically joined together from edge to edge to form an integrated layer of graphene oxide-like entities. In addition, the HA / CHA layer first undergoes a heat-induced reduction reaction, resulting in a reduction in oxygen content of about 5% or less. This treatment results in a reduction in the inter-graphene spacing from about 0.8-1.2 nm (when dry) to about 0.4 nm and an increase in in-plane thermal conductivity from about 100 W / mK to 500 W / mK. Even in such a low temperature range, some chemical linkage between HA / CHA sheets occurs. The HA / CHA sheets remain well aligned, but the graphene interplanetary spacing remains relatively large (0.4 nm and above). Many O-containing functional groups continue to exist.

The highest or final HTT received by the GO mass may be divided into three distinct HTT regimes:
Regime 2 (300 ° C to 1,500 ° C): In this predominantly chemical linkage regime, additional thermal reduction and extensive compounding, polymerization, and cross-linking between adjacent HA / CHA sheets occur. Chemical linkages between HA / CHA and graphene sheets (eg GO sheets) also occur if present. The oxygen content is typically reduced to less than 1% after chemical ligation, resulting in a reduction in the inter-graphene spacing to about 0.35 nm. Some initial graphitization is such a low temperature, in sharp contrast to conventional graphitizable materials (such as polyimide carbide films), which typically require temperatures as high as 2,500 ° C to initiate graphitization. This means that it has already begun in. This is another distinct feature of the HOHA film of the present invention and its manufacturing process. These chemical linkage reactions result in an increase in in-plane thermal conductivity to 850 to 1,250 W / mK and / or in-plane electrical conductivity to 3,500 to 4,500 S / cm.
Regime 3 (1,500-2,500 ° C.): In this ordering and regraphitization regime, extensive graphitization or graphene surface assimilation occurs, resulting in a significantly improved degree of structural ordering. As a result, the oxygen content is typically reduced to 0.01% and the inter-graphene spacing is reduced to about 0.337 nm (1% to about 80% graphitization, depending on the actual HTT and time). To achieve). The improved degree of order is also due to the increase in in-plane thermal conductivity to> 1,300 to 1,500 W / mK and / or in-plane electrical conductivity to 5,000 to 7,000 S / cm. It will be reflected.
Regime 4 (above 2,500 ° C): In this recrystallization and completion regime, extensive migration and removal of grain boundaries and other defects occurs, a number greater than the original grain size of the starting HA / CHA sheet. It results in the formation of near-perfect single or polycrystalline graphene crystals with large grain grains, which can be orders of magnitude larger. The oxygen content is essentially eliminated, typically 0.01% to 0.1%. The inter-graphene spacing is reduced to about 0.3354 nm (80% to nearly 100% graphitization), which corresponds to the inter-graphene spacing of a complete graphite single crystal. Very interestingly, graphene polycrystals have a perfect orientation, with all graphene faces closely packed and joined, with all faces aligned in one direction. Such a fully oriented structure is also produced using HOPG produced by simultaneously subjecting pyrolytic graphite to ultrahigh temperature (3,400 ° C.) under ultrahigh pressure (300 kg / cm ^2). No. Highly oriented graphene structures can achieve the highest degree of perfection using significantly lower temperatures and ambient (or slightly higher compression) pressures. The structure thus obtained exhibits in-plane thermal conductivity in the range of 1,500 to slightly> 1,700 W / mK and in-plane electrical conductivity in the range of 15,000 to 20,000 S / cm. ..

The highly oriented HA-derived structures of the present invention more generally contain the first two regimes (1-10 hours), including at least the first regime (which typically requires 1 to 24 hours in this temperature range). More generally the first three regimes (preferably 0.5-5 hours in regime 3), and most generally all four regimes (regime 4 is 0.5-2 hours), including preferred). It can be obtained by heat treating the HA / CHA layer using a temperature program that includes (may be introduced to achieve the highest conductivity during).

The X-ray diffraction pattern was obtained using an X-ray diffractometer equipped with CuKcv radiation. Diffraction peak shifts and widening were calibrated using a silicon powder standard. For the degree of graphitization, g uses the formula d ₀₀₂ = 0.3354 g + 0.344 (1-g) of _{mailing (in the formula, d 002} is the intermediate layer spacing of graphite or graphene crystals in nm units). Then, it was calculated from the X-ray pattern. This equation is _{valid only when d 002} is about 0.3440 nm or less. _{HOHA with d 002} above 0.3440 nm acts as a spacer to increase the spacing between graphene oxygen-containing functional groups (eg, -OH,> O, and -COOH on the surface of the graphene-like plane). Reflects the existence of.

Another structural index that can be used to characterize the degree of ordering of the HOHA-derived graphite film of the present invention and conventional graphite crystals is the full width at half maximum of the (002) or (004) reflection locking curve (X-ray diffraction intensity). It is a "mosaic spread" represented by. This degree of order characterizes the graphite or graphene crystal size (or grain size), the amount of grain boundaries and other defects, and the preferred grain orientation. A nearly perfect single crystal of graphite is characterized by having a mosaic spread value of 0.2-0.4. Most of our HOHA-derived graphite samples have a mosaic spread value in this range of 0.2-0.4 (when manufactured using a heat treatment temperature (HTT) of 2,500 ° C. or higher). However, some values range from 0.4 to 0.7 when the HTT is between 1,500 and 2,500 ° C, and 0.7 to 0.7 when the HTT is between 300 and 1,500 ° C. It is in the range of 1.0.

HA or graphene may be functionalized by various chemical pathways. In one preferred embodiment, the resulting functionalized HA or functionalized graphene (collectively referred to as Gn) generally has the following formula (e): [Gn] −−R _m.
(In the formula, m is the number of different functional group types (typically between 1 and 5) and R is SO ₃ H, COOH, NH ₂ , OH, R'CHOH, CHO, CN, COCl. , Khalid, COSH, SH, COOR ', SR', SiR '3, Si (- OR' -) y R '3 -y, Si (- O - SiR' 2 -) OR ', R _{'', Li, AlR '2} , Hg - X, TlZ 2 and Mg - is selected from X, where y is 3 an integer, R' is hydrogen, alkyl, aryl, cycloalkyl or aralkyl, Cycloaryl, or poly (alkyl ether), R'' is fluoroalkyl, fluoroaryl, fluorocycloalkyl, fluoroaralkyl or cycloaryl, X is halide, Z is carboxylate or trifluoroacetate. ) May have.

Assuming that a polymer such as an epoxy resin can be combined with HA or a graphene sheet to produce a coating composition, then functional group-NH ₂ is of particular importance. For example, a commonly used curing agent for epoxy resins is diethylenetriamine (DETA), which can have two or more -NH ₂ groups. One of the -NH ₂ groups may be bonded to the edge or surface of the graphene sheet, and the remaining unreacted -NH ₂ groups are available for later reaction with the epoxy resin. Such an arrangement provides a good interfacial bond between the HA (or graphene) sheet and the resin additive).

Other useful chemical functional groups or reactive molecules are amidoamines, polyamides, aliphatic amines, modified aliphatic amines, alicyclic amines, aromatic amines, anhydrides, ketimine, diethylenetriamine (DETA), triethylene-tetramine. It may be selected from the group consisting of (TETA), tetraethylene-pentamine (TEPA), polyethylene polyamines, polyamine epoxy adducts, phenolic hardeners, non-bromination hardeners, non-amine hardeners, and combinations thereof. These functional groups are polyfunctional and are capable of reacting with at least two species from at least two ends. Most importantly, they can utilize one of their ends to join to the edge or surface of graphene or HA, and during the subsequent curing step, one or two other ends. Can react with the resin in.

Above [Gn] - _{R m} may be further functionalized. The obtained CFG has the formula:
[Gn] - _A m,
(In the formula, A is OY, NHY, O = C-OY, P = C-NR'Y, O = C-SY, O = C-Y, --CR'1--OY, Selected from N'Y or C'Y, Y is the appropriate functionality of a protein, peptide, amino acid, enzyme, antibody, nucleotide, oligonucleotide, antigen, or enzyme substrate, enzyme inhibitor or transition state analog of the enzyme substrate. or a group, R '- OH, R' - NR '2, R'SH, R'CHO, R'CN, R'X, R'N + (R') 3 X -, R ' _{SiR '3, R'Si (- OR} ' -) y R '3-y, R'Si (- O - SiR' 2 -) OR ', R' - R '', R ' −−N−−CO, (C ₂ H ₄ O−−) _w H, ( _{−−C 3} H ₆ O−−) _w H, ( _{−−C 2} H ₄ O) _w −−R ′, (C ₃ H ₆ O) _{W − −} R', selected from R', w is an integer greater than 1 and less than 200).

Also, functionalize the HA and / or graphene sheet,
Formula: [Gn]-[R'-A] _m
Compositions having (where m, R'and A are defined above in the formula) may be prepared. In addition, the composition of the present invention contains CHA to which a specific cyclic compound is adsorbed. These include the formula: [Gn] −− [X−−R _a ] _m
(In the formula, a is a number that is zero or less than 10, X is a polynuclear aromatic, polyheteronuclear aromatic or metallo polyheteronuclear aromatic moiety, and R is defined above). Contains the composition of the substance. Preferred cyclic compounds are planar. More preferred cyclic compounds for adsorption are porphyrins and phthalocyanines. The adsorbed cyclic compound may be functionalized. For such compositions, the formula:
[Gn] −− [X−−A _a ] _m
Compounds (in the formula, m, a, X and A are defined above) are included.

The functionalized HA or graphene of the present invention can be prepared directly by sulfonation, electrophilic addition, or metalation of the oxygenated GO surface. Graphene or HA sheets can be processed prior to contact with the functionalizing agent. Such processing may include the step of dispersing the graphene or HA sheet in a solvent. In some cases, the sheet may then be filtered and dried prior to contact. One particularly useful type of functional group is the carboxylic acid moiety, which is naturally present on the surface of HA when prepared from the acid intercalation pathways discussed above. If an additional amount of carboxylic acid is required, the HA sheet may be subjected to chlorate, nitric acid, or ammonium persulfate oxidation.

Carboxylic acid-functionalized graphene sheets are particularly useful as they can serve as a starting point for preparing other types of functionalized graphene or HA sheets. For example, alcohols or amides can be easily linked to acids to give stable esters or amides. If the alcohol or amine is part of a bifunctional or polyfunctional molecule, the O- or NH-linkage leaves other functional groups such as side groups. These reactions can be carried out using any of the methods known in the art developed for esterifying or aminating carboxylic acids with alcohols or amines. Examples of these methods are described in G.I. W. Anderson, et al. , J. Amer. Chem. Soc. It can be found in 96, 1839 (1965), the contents of which are incorporated herein by reference in their entirety. To introduce the amino group directly onto the graphite fibrils, the fibrils are treated with nitric acid and sulfuric acid to give the fibrils nitride, then the nitriding form is chemically reduced with a reducing agent such as sodium dithionite for amino functionalization. Get fibril.

We have found that the aforementioned functional groups can be attached to the surface or edges of the HA or graphene sheet for one or several of the following purposes: (a) Improvements of graphene or HA in the desired liquid medium. Due to the dispersed dispersion, (b) due to the increased solubility of graphene or HA in the liquid medium, a sufficient amount of graphene or HA sheet in this liquid exceeds the critical body integration factor for the formation of the liquid crystal phase. To allow it to be dispersed in (c) a thin film of graphene or HA, or otherwise discrete sheets, to be able to cast or coat with increased film forming ability. (D) To improve the ability of graphene or HA sheets to be oriented to improve flow characteristics, and (e) Graphene or HA sheets are chemically linked and assimilated to form larger or wider graphene surfaces. To increase the ability to do.

The present invention also provides a rechargeable battery containing the graphene oxide thin film bonded metal foil of the present invention as an anode current collector and / or a cathode current collector. This can be any rechargeable battery, for example, a zinc-air cell, a nickel metal hydride cell, a sodium ion cell, a sodium metal cell, a magnesium ion cell, or a magnesium metal cell, to name a few. can. The battery of the present invention can be a rechargeable lithium battery containing a unit graphene layer as an anode current collector or a cathode current collector, the lithium battery being a lithium-sulfur cell, a lithium-sulene cell, a lithium sulfur. It can be a / selenium cell, a lithium ion cell, a lithium-air cell, a lithium-graphene cell, or a lithium-carbon cell. Another embodiment of the present invention is a capacitor containing the current collector of the present invention as an anode current collector or a cathode current collector, the capacitor being a symmetric ultracapacitor, an asymmetric ultracapacitor cell, a hybrid supercapacitor-battery. It is a cell or a lithium ion capacitor cell.

As an example, the present invention presents a cathode containing a current collector on the anode side, a lithium film or foil as the anode, a porous separator / electrolyte layer, and a cathode active material (eg, lithium-free V ₂ O ₅ and Mn _{O 2).} , And a rechargeable lithium-metal cell composed of a current collector. Either or both of the anode and cathode current collectors can be HA-based current collectors of the invention (ie obtained from highly oriented thin films of HA or HA / graphene mixtures).

Another example of the present invention is a current collector on the anode side, a graphite or lithium titanate anode, a porous separator immersed in a liquid or gel electrolyte, a cathode containing a cathode active material (eg, activated carbon with a high specific surface area). , And a lithium ion capacitor (or hybrid super capacitor) composed of a current collector. Further, either or both of the anode current collector and the cathode current collector can be the HA-based current collector of the present invention.

Yet another example of the present invention is another lithium ion capacitor or hybrid supercapacitor, which is immersed in an anode-side current collector, a graphite anode (and a sheet of lithium foil as part of the anode), and a liquid electrolyte. It is composed of a porous separator, a cathode containing a cathode active material (for example, activated carbon having a high specific surface area), and a current collector. Further, either or both of the anode current collector and the cathode current collector can be the HA-based current collector of the present invention.

Yet another example of the present invention is an anode-side current collector, a porous nanostructured anode (eg, returning lithium ions can deposit on top during cell recharging, surface-stabilized lithium powder. High surface area graphene sheets with lithium foil sheets where particles are mixed or adhered to nanostructures), porous separators immersed in a liquid electrolyte, graphene-based cathode active materials (eg, cells) A lithium-graphene cell composed of a cathode containing graphene, graphene oxide, or graphene fluoride sheet) having a high specific surface area that captures lithium ions during discharge, and a cathode current collector. Further, either or both of the anode current collector and the cathode current collector can be the HA-based current collector of the present invention.

Example 1: Humic acid from Leonardite and reduced humic acid Humic acid can be extracted from Leonardite in very high yield (range 75%) by dispersing Leonardite in a basic aqueous solution (pH 10). Subsequent acidification of the solution gives a precipitate of humic acid powder. In the experiment, 3 g of leonaldite was dissolved under magnetic agitation with 300 ml of double deionized water containing a _{1 M KOH (or NH 4 OH) solution.} The pH value was adjusted to 10. The solution was then filtered to remove any large particles or any residual impurities.

A series of coatings of the resulting humic acid dispersion on the surface of a Cu or Ti foil containing HA alone or with a graphene oxide sheet (GO prepared in Example 3 described below). An HA-bonded Cu foil or Ti foil film was formed and subsequently heat-treated to obtain a type-A current collector.

For comparison, a similar film was cast onto the glass surface and then stripped prior to subsequent heat treatment to prepare a Type-B current collector.

Example 2: Preparation of humic acid and HA-bonded metal foil current collector from coal In a typical procedure, 300 mg of coal was suspended in concentrated sulfuric acid (60 ml) and nitric acid (20 ml), followed by 2 hours. The cup was sonicated. The reaction was then stirred and heated in an oil bath at 100 ° C. or 120 ° C. for 24 hours. The solution was cooled to room temperature, poured into a beaker carrying 100 ml of ice, followed by the addition of NaOH (3M) until the pH value reached 7.

In one experiment, the neutralized mixture was then filtered through a 0.45 mm polytetrafluoroethylene membrane and the filtrate was dialyzed in a 1,000 Da dialysis bag for 5 days. Due to the larger humic acid sheet, cross-flow extrafiltration can be used to reduce the time to 1-2 hours. After purification, the solution was concentrated using rotary evaporation to give a solid humic acid sheet. How many of these humic acid sheets alone and their mixture with graphene sheets are redispersed in a solvent (ethylene glycol and alcohol, separately) for subsequent casting or coating on Al and stainless steel foils. A sample of the dispersion was obtained. Both type-A and type B current collectors were prepared.

Example 3: Preparation of Graphene (GO) Sheet from Natural Graphite Powder Natural graphite from Ashbury Carbons was used as a starting material. GO was obtained according to a known improved Hummers method that required two oxidation steps. In a typical procedure, the first oxidation was achieved under the following conditions: 1100 mg of graphite was placed in a 1000 mL boiling flask. Next, 400 mL of a concentrated aqueous solution of 20 g of K ₂ S ₂ O ₈ , 20 g of P ₂ O ₅ and H ₂ SO ₄ (96%) was added into the flask. The mixture was heated to reflux for 6 hours and then allowed to stand at room temperature for 20 hours. Oxidized graphite was filtered and washed with abundant distilled water until a pH value> 4.0 was reached. The wet cake-like material was recovered at the end of this first oxidation.

For the second oxidation process, the pre-collected wet cake was placed in a boiling flask containing 69 mL of a concentrated aqueous solution _{of H 2} SO _{4 (96%).} The flask was held in an ice bath as 9 g of KMnO _{4 was added slowly.} Care was taken to avoid overheating. The resulting mixture was stirred at 35 ° C. for 2 hours (sample color changed to dark green), after which 140 mL of water was added. After 15 minutes, it was stopped the reaction by adding water and 30 _wt% H 2 _{O 2} in aqueous solution 15mL of 420 mL. At this stage, the color of the sample changed to bright yellow. To remove metal ions, the mixture was filtered and washed with 1:10 aqueous HCl. The collected material was gently centrifuged at 2700 g and washed with deionized water. The final product was a wet cake containing 1.4% by weight GO as estimated from the dry extract. The wet cake material diluted in deionized water was then loosely sonicated to give a liquid dispersion of GO plate lit.

By another criterion, a mixture of GO and humic acid with various GO ratios (1%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 99). %) The aqueous suspension was prepared and coated with a slot die to produce thin films of various compositions.

Example 4: Preparation of Alignment Film Containing Mixture of Humic Acid and Pure Graphene Sheet (0% Oxygen) In a typical procedure, 1,000 mL of 5 grams of graphite flakes finely ground to a size of about 20 μm or less. Suspension was obtained by dispersing in deionized water (Zonyl® FSO manufactured by DuPont, containing 0.1% by weight of a dispersion aid). An ultrasonic energy level of 85 W (Branson S450 Ultrasonicator) was used for peeling, separating and grinding graphene sheets for 15 minutes to 2 hours. The obtained graphene sheet is pure graphene that is never oxidized, contains no oxygen, and is relatively free of defects. Pure graphene is essentially free of any non-carbon elements.

The sonicated suspension contains a pure graphene sheet dispersed in water and a surfactant dissolved therein. Humic acid was then added to the suspension and the resulting mixture suspension was further sonicated for 10 minutes to promote uniform dispersion and mixing. The dispersion was then coated on Cu and Ti foils prior to heat treatment and on glass and PET films for comparison.

Example 5: Preparation of highly oriented graphite film from a mixture of graphene fluoride sheet and humic acid Although several methods were used to produce GF, only one method is described herein as an example. In a typical procedure, a high peel graphite (HEG) was prepared from Compound С ₂ F · xClF ₃ intercalated. The HEG was further fluorinated by the vapor of chlorine trifluoride to give fluorinated high exfoliation graphite (FHEG). The precooled Teflon reactor was filled with 20-30 mL of liquid precooled ClF ₃ and the reactor was closed and cooled to liquid nitrogen temperature. Next, 1 g or less of HEG was placed in a container located in the reactor, which had a hole for _{ClF 3 gas to enter.} In 7 days, a gray-beige product with _{approximation C 2 F was formed.}

A small amount of FHEG (about 0.5 mg) was then mixed with 20-30 mL of organic solvent (methanol and ethanol, separately) and subjected to sonication (280 W) for 30 minutes to a homogeneous yellowish dispersion. Brought about the formation of. Humic acid was then added to these dispersions at various HA to GF ratios. The dispersion was then made into a thin film supported by Cu foil using a comma coating. Next, the highly oriented HA film was heat-treated to various degrees to obtain a highly conductive graphite film.

Example 6: Preparation of a HOHA film containing a nitrogenized graphene sheet and humic acid The graphene oxide (GO) synthesized in Example 3 is finely ground with different proportions of urea, and the pelletized mixture is atomized for 30 seconds. During the heating, it was heated in a microwave reactor (900 W). The product was washed several times with deionized water and vacuum dried. In this method graphene oxide was simultaneously reduced and doped with nitrogen. Products with graphene / urea mass ratios of 1: 0.5, 1: 1 and 1: 2 were obtained, and the nitrogen content of these samples was 14.7, 18. It was 2 and 17.5% by weight. These nitrogenized graphene sheets remain dispersible in water. Various amounts of HA with an oxygen content of 20.5% to 45% were added to the suspension.

Next, the obtained suspension of the nitrogenized graphene-HA dispersion was coated on a plastic film substrate to form a wet film, and then they were dried and peeled from the plastic film, 80-2. Highly oriented humic acid (HOHA) film (when final HTT <1,500 ° C) or highly ordered and conductive graphite film (when above 1,500 ° C), subjected to heat treatment at various heat treatment temperatures of 900 ° C. Got Next, these films were bonded to the Ti and Cu surfaces using a resin binder to produce a Type-B current collector. In addition, for comparative purposes, a certain amount of suspension of graphene-HA dispersion was coated on the Ti and Cu foil surfaces to form wet films, then dried, respectively. , 1,500 ° C and 1,250 ° C.

Example 7: Preparation of nematic liquid crystal from humic acid sheet and high conductive film produced from it A humic acid aqueous dispersion was prepared by dispersing the HA sheet in deionized water by medium sonication treatment. All acidic or ionic impurities in the dispersion were removed by dialysis, an important step for the formation of liquid crystals.

The low concentration dispersion (typically 0.05-0.6% by weight) immobilized for a sufficiently long time (usually greater than 2 weeks) was macroscopically phase-separated into two phases. The low-density upper phase is optically isotropic, while the high-density lower phase showed significant optical birefringence between the two crossed polarizing plates. A typical nematic schlieren texture consisting of dark and bright brushes was observed in the lower phase. This is a biphasic behavior, where the isotropic phase and the nematic phase coexist. Due to the large polydispersity of HA molecules, the two-phase composition range is significantly wider. It may be pointed out that ionic strength and pH values have a significant effect on the stability of HA LCDs. Electrostatic repulsion from dissected surface functional groups such as carboxylate plays an important role in the stability of HA liquid crystals. Therefore, the coagulation of the HA sheet was increased by reducing the repulsive interaction by increasing the ionic strength or lowering the pH value.

When the HA sheet occupies a weight fraction of 1.1%, virtually all HA sheets form a liquid crystal phase, allowing the liquid crystal to survive by gradually increasing the concentration of HA in the range of 6% to 16%. We have observed that it can be done. The prepared humic acid dispersion exhibited a chocolate-milky appearance that was heterogeneous to the naked eye. This milky appearance can be mistaken for condensation or precipitation of graphene oxide, but in reality it is a nematic liquid crystal.

A thin film of dried HA was obtained by a step of distributing and coating the HA suspension on a polyethylene terephthalate (PET) film with a slurry coater and a step of removing the liquid medium from the coated film. The dried film was stripped from the PET film and became a free-standing film before heat treatment. Furthermore, the HA suspension was coated on a Cu foil or Ti surface and then dried. Each film (both free-standing film stripped from PET and Ti or Cu-supported film) was then subjected to different heat treatments, typically at 80 ° C. for 1-10 hours. Includes chemical ligation and heat reduction treatment at a first temperature of ~ 300 ° C. and a second temperature of 1,500 ° C. to 2,850 ° C. for 0.5-5 hours. The Cu-supported film and the Ti-supported film were simply heat-treated to 1,250 ° C and 1,500 ° C, respectively. By these heat treatments, the HOHA film was changed to a highly conductive graphite film (HOGF) also under compressive stress.

Several dried HA layers (HOHA films) and internal structure (crystal structure and orientation) of HOGF were investigated at different stages of heat treatment. A layer of dried HOHA before heat treatment, a HOHA film heat-treated at 150 ° C. for 5 hours, and an X-ray diffraction curve of the obtained HOGF were obtained. The peak at about 2θ = 12 ° in the dried HOHA layer corresponds to _{the spacing (d 002) between graphenes at about 0.75 nm.} After some heat treatment at 150 ° C, the dried film shows the formation of a hump centered at 22 °, which initiates a process of reducing the spacing between the surfaces, indicating the start of the chemical ligation and ordering process. Show that you did. The heat treatment temperature of 2,500 ° C. over 1 hour reduced the d ₀₀₂ spacing of the film (not bonded to the metal foil) to about 0.336, which is close to 0.3354 nm for the graphite single crystal.

The heat treatment temperature of 2,750 ° C. over 1 hour, _{d 002} spacing film not bonded to the metal surface is equal to _{d 002} spacing of graphite monocrystal, reduced to about 0.3354 nm. Further, the second diffraction peak having high intensity appears at 2θ = 55 °, which corresponds to the X-ray diffraction from the (004) plane. The (004) peak intensity, or I (004) / I (002) ratio to the (002) intensity on the same diffraction curve is a good indication of the crystal perfection of the graphene plane and the preferred orientation. For all conventional graphite materials heat treated at temperatures below 2,800 ° C., the (004) peak is either absent or relatively weak, with an I (004) / I (002) ratio < It is known in the art that it is 0.1. The I (004) / I (002) ratio of graphite materials heat-treated at 3,000 to 3,250 ° C. (eg, highly oriented pyrolytic graphite, HOPG) is in the range of 0.2 to 0.5. In contrast, HOGF prepared from HA liquid crystal based films using a final HTT of 2,750 ° C. for 1 hour had an I (004) / I (002) ratio of 0.77 and 0.21. Shows a mosaic spread value of, showing a nearly perfect graphene single crystal with a very high degree of favorable orientation.

The "mosaic spread" value is obtained from the full width at half maximum of the (002) reflection of the X-ray diffraction intensity curve. This indicator for degree of order characterizes graphite or graphene crystal size (or grain size), amount of grain boundaries and other defects, and preferred grain orientation. A nearly perfect single crystal of graphite is characterized by having a mosaic spread value of 0.2-0.4. Most of our HA-derived HOGFs have a mosaic spread value in this range of 0.2-0.4 when manufactured using a final heat treatment temperature of 2,500 ° C. or higher.

It was pointed out that the I (004) / I (002) ratios of all the dozens of flexible graphite foil compacts investigated were all << 0.05, and in many cases virtually nonexistent. You may leave it. The I (004) / I (002) ratio of all graphene paper / membrane samples prepared by the vacuum auxiliary filtration method is <0.1 even after heat treatment at 3,000 ° C. for 2 hours. The HOHA film of the present invention is fundamentally different from conventional graphene / GO / RGO sheet / plate lit (NGP) paper / film / film, in addition to all pyrolysis graphite (PG) and flexible graphite (FG). These observations further supported the idea that they are a novel and distinct class of material that are different from each other.

The inter-graphene spacing values of both HA liquid crystal suspension-derived HOGF samples obtained by heat treatment at various temperatures over a wide temperature range are summarized in FIG. 5 (A). Corresponding oxygen content values are shown in FIG. 5 (B). The data in FIGS. 5 (A) and 5 (B) are plotted again in FIG. 5 (C) to show the correlation between the inter-graphene spacing and the oxygen content. A close scrutiny of FIGS. 5 (A) to 5 (C) results in four HTT ranges (100-300 ° C, 300-1500 ° C) that result in four respective oxygen content ranges and inter-graphene spacing ranges. , 1,500-2,000 ° C, and> 2,000 ° C). The thermal conductivity of the corresponding samples of the HA liquid crystal-derived HOGF test piece and the flexible graphite (FG) foil sheet, also plotted as a function of the same final heat treatment temperature range, is summarized in FIG. 5 (D). All these samples have comparable thickness values.

It was pointed out that the heat treatment temperature of only 500 ° C. is sufficient to keep the average interplanetary spacing below 0.4 nm and is getting closer and closer to the average interplanetary spacing of natural graphite or the average interplanetary spacing of graphite single crystals. Should be kept. The advantage of this method is that the HA liquid crystal suspension method reassembles, reorients, and chemically assimilates the planar HA sheet so that all graphene-like surfaces are now larger in lateral dimensions (original HA). It means that we were able to form a unified structure (significantly larger than the length and width of the hexagonal carbon plane of the molecule) and essentially parallel to each other. It already has a thermal conductivity of> 623 W / mk (from HA only) or> 900 W / mk (from a mixture of HA + GO) using 300-400 W / mK (using HTT at 500 ° C) and HTT at 700 ° C. The rate is generated, which is 3 to 4 times greater than the value of the corresponding flexible graphite foil (200 W / mK). Furthermore, the tensile strength of the HOGF sample can reach 90-125 MPa (FIG. 7 (A)).

Using an HTT of only 1,000 ° C., the resulting highly oriented HA film exhibits thermal conductivity of 756 W / mK (from HA only) and 1,105 W / mK (from HA-GO mixture) respectively. This is in stark contrast to the observed 268 W / mK of flexible graphite foil using the same heat treatment temperature. In fact, no matter how high the HTT (eg at 2,800 ° C.), the flexible graphite foil shows only a thermal conductivity below 600 W / mK. At 2,800 ° C. HTT, the HOGF layer of the present invention provides a thermal conductivity of 1,745 W / mK for the layer obtained from a mixture of HA and GO (FIGS. 4 (A) and 5 (D)). ). It is further pointed out that, as shown in FIG. 4 (A), the thermal conductivity value of the graphite film derived from the HA / GO mixture is consistently higher than the thermal conductivity value of the corresponding graphite film derived from graphene oxide. You can leave it. This surprising effect is further discussed in Example 8.

Scanning electron microscopy (SEM), transmission electron microscopy (TEM) photography of lattice imaging of graphene layers, and selected area diffraction (SAD), brightfield (BF), and darkfield (DF) images are also performed. Then, the structure of the unit graphene material was characterized. For measurement of cross-sectional views of the film, the sample was embedded in a polymer base, sliced using an ultramicrotome and etched with Ar plasma.

Close scrutiny and comparison of FIGS. 2, 3 (A), and 3 (B) shows that the graphene-like layers within the HOGF are substantially oriented parallel to each other. However, this is not the case for flexible graphite foil and graphene oxide paper. The tilt angle between the two identifiable layers in the highly conductive graphite film is generally less than 10 degrees and primarily less than 5 degrees. In contrast, there are so many broken graphite flakes, kinks, and misalignments in flexible graphite that many of the angles between the two graphite flakes are greater than 10 degrees, some as much as 45 degrees. There is (Fig. 2). Not bad at all, but the misalignment between the graphene plate lits in the NGP paper (FIG. 3B) is also high and there are many gaps between the plate lits. The HOGF entity is essentially gap-free.

FIG. 4 (A) shows the thermal conductivity of HA / GO-derived film, GO-derived film, HA suspension-derived HOGF, and flexible graphite (FG) foil, all plotted as a function of the final HTT, respectively. Indicates a value. These data clearly demonstrated the superiority of the HA / GO-derived HOGF structures of the present invention with respect to the achievable thermal conductivity at a given heat treatment temperature.
1) HA / GO liquid crystal suspension-derived HOGF seems to be superior to GO gel-derived HOGF in thermal conductivity at the same final heat treatment temperature. Strong oxidation of the graphene sheet in the GO gel would have resulted in high defects on the graphene surface even after thermal reduction and regraphitization. However, the presence of HA molecules appears to be able to help repair defects or bridge the gaps between GO sheets.
2) Highly oriented films obtained from HA alone show slightly lower thermal conductivity values than films obtained from GO alone, but HA is naturally abundant as a material, which is desirable for producing HA. Does not require the use of no chemicals. HA is an order of magnitude cheaper than natural graphite (a raw material for GO) and 2-4 orders of magnitude cheaper than GO.
3) For comparison, we also obtained a conventional highly oriented pyrolytic graphite (HOPG) sample from the polyimide (PI) carbonization pathway. The polyimide film was carbonized in an inert atmosphere at 500 ° C. for 1 hour, at 1,000 ° C. for 3 hours, and at 1,500 ° C. for 12 hours. Next, the carbonized PI film was graphitized at a temperature in the range of 2,500 to 3,000 ° C. under compressive force for 1 to 5 hours to form a conventional HOPG structure.

FIG. 4B shows the thermal conductivity values of HA / GO suspension-derived HOGF, HA suspension-derived HOGF, and polyimide-derived HOPG, all plotted as a function of final heat treatment temperature. These data show that conventional HOPGs made using the carbonized polyimide (PI) pathway are with HA / GO-derived HOGF given the same HTT for the same length of heat treatment time. It is consistently lower in thermal conductivity in comparison. For example, PI-derived HOPG exhibits a thermal conductivity of 820 W / mK after graphitization treatment at 2,000 ° C. for 1 hour. At the same final graphitization temperature, HA / GO-derived HOGF exhibits a thermal conductivity value of 1,586 W / mK. It may also be pointed out that PI is several orders of magnitude more expensive than HA and that the production of PI requires the use of some environmentally undesired organic solvents.
4) These observations demonstrated a clear significant advantage of using the HA / GO or HA suspension method of producing HOGF over the conventional PG method of producing oriented graphite crystals. As a matter of fact, no matter how long the graphitization time is for HOPG, the thermal conductivity is always lower than the thermal conductivity of HA / GO liquid crystal-derived HOGF. It is also surprising to discover that humic acid molecules can be chemically linked to each other to form a strong and highly conductive graphite film. Highly oriented HA films (including highly oriented HA / GO films), and subsequently heat-treated alternative forms, are flexible graphite (FG) with respect to chemical composition, crystal and defect structure, crystal orientation, morphology, manufacturing process, and properties. It is clear that foil, graphene / GO / RGO paper / film, and pyrolytic graphite (PG) are fundamentally different and clearly distinguishable.
5) The above conclusions are further supported by the data in FIG. 4 (C) showing the values of electrical conductivity of HA / GO suspension-derived and HA suspension-derived HOGF, where HOGF is the final HTT to be investigated. It is far superior to the electric conductivity value of the FG foil sheet over the entire range.

Example 8: Effect of addition of graphene on the properties of HA-based highly oriented graphite film and the resulting graphite film Various amounts of graphene oxide (GO) sheet are added to the HA suspension to add HA and A mixture suspension was obtained in which the GO sheet was dispersed in a liquid medium. HOGF samples of various GO ratios were then produced according to the same procedure as described above. The thermal conductivity data of these samples are summarized in FIG. 6, which shows that the thermal conductivity value of HOGF produced from the HA-GO mixture is higher than the thermal conductivity value of the HOGF film produced from only a single component. Indicates high.

Even more surprising is the synergistic effect that can be observed when both the HA sheet and the GO sheet coexist in the proper proportions. HA appears to be able to help GO sheets (known to be highly defective) repair from those otherwise defective structures. It is also possible that HA molecules are significantly smaller in size than GO sheets / molecules and can close the gaps between GO molecules and react with them to crosslink the gaps. These two factors probably result in significantly improved conductivity.

Example 9: Tensile Strength of Various Graphene Oxide-Derived HOHA Films A series of HA / GO dispersion-derived HOGF, GO dispersion-derived HOGF, and HA-derived HOGF films were prepared using the same final heat treatment temperature for all materials. Prepared. A universal material tester is used to determine the tensile properties of these materials. The tensile strength and modulus of these various samples prepared over a wide range of heat treatment temperatures are shown in FIGS. 7 (A) and 7 (B), respectively. For comparison, some tensile strength data for RGO paper and flexible graphite foil are also summarized in FIG. 7 (A).

These data show that the tensile strength of the graphite foil-derived sheet increases slightly with the final heat treatment temperature (14-29 MPa) and when the final heat treatment temperature increases to 700-2,800 ° C., GO paper (compression of GO paper). / It is shown that the tensile strength of the heating sheet) increases to 23 to 52 MPa. In contrast, the tensile strength of HA-derived HOGF increases significantly to 28-93 Mpa for the same range of heat treatment temperatures. Most dramatically, the tensile strength of HA / GO suspension-derived HOGF increases significantly to 32-126 Mpa. This result is very interesting and HA / GO and HA dispersions are highly oriented / aligned chemically active HA / GO and HA sheets / molecules that can be chemically linked and assimilated during heat treatment. Although contained, on the other hand, it further reflects the idea that graphene plate lit in conventional GO paper and graphite flakes in FG foil are essentially dead plate lit. Highly oriented films based on HA or HA / GO and subsequent graphite films are themselves a new class of material.

As a reference point, the film obtained by simply spraying a HA-solvent solution onto the glass surface to dry the solvent has no strength (it is so brittle that it breaks the film just by touching it with a finger. can do). After heat treatment at a temperature of> 100 ° C., the film breaks apart (breaks into innumerable pieces). In contrast, a highly oriented HA film, where all HA molecules or sheets are highly oriented and packed together, may have a tensile strength of> 24 MPa when heat treated at 150 ° C. for 1 hour. It becomes a film with structural integrity.

Example 10: Novel effect of metal foil on heat-induced chemical ligation of humic acid molecules Figure 8 shows the thermal conductivity values of the three HA-derived highly oriented films. The first film was obtained by heat-treating the HA film peeled from the glass surface. The second film was coated on the Ti surface and the film was bonded to the Ti surface during the heat treatment. The third film was coated on the Cu foil surface and bonded to the Cu foil surface during the heat treatment. At the same final heat treatment temperature, the metal foil-supported HA film exhibits significantly higher thermal conductivity values compared to the thermal conductivity values of the film that is stripped from the PET film surface prior to heat treatment. Cu and Ti foils appear to be able to provide some catalytic effect on heat-induced chemical ligation or assimilation between humic acid molecules in close contact with Cu or Ti. This is really unexpected. Even more surprising is the discovery that the difference in conductivity is very large. Further, when supported on a Cu foil, the HA film after heat treatment at 1,250 ° C. exhibits a thermal conductivity of 1,432 W / mK. The same values were achieved with HA-derived films after heat treatment at 2,500 ° C. for the same time without the advantage of being catalyzed by Cu or Ti.

Example 11: Li-S cells containing a fumic acid-bonded metal foil current collector on the anode side and the cathode side Three (3) Li-S cells were prepared and tested, and each of them was a lithium foil active material as an anode. It has a sulfur / expanded graphite composite (75/25 weight ratio) as the cathode active material, 1M LiN (CF ₃ SO ₂ ) ₂ in DOL as the electrolyte, and Celgard 2400 as the separator. The first cell (reference cell for comparison) contains a Cu foil having a thickness of 10 μm as an anode current collector and an Al foil having a thickness of 20 μm as a cathode current collector. The second cell (another reference cell for comparison) has a 10 μm thick GO-resin layer as the anode current collector and a 14 μm RGO coated Al foil sheet as the cathode current collector. The third cell has an HA-bonded Cu foil (total thickness 12 μm) of the present invention as an anode current collector and a sheet of HA-coated Al foil having a thickness of 20 μm as a cathode current collector.

The charge storage capacity was periodically measured and recorded as a function of the number of cycles. The specific discharge capacity referred to herein counts the weight of the cathode active material, conductive additive or support, and binder, but excludes the current collector, per unit mass of the cathode complex. It is the total charge that is put into the cathode during discharge. The specific energy and output values shown in this section are based on total cell weight, including anodes and cathodes, separators and electrolytes, current collectors, and packing materials. Morphological or microstructural changes of the selected sample after a desired number of repeated charging and recharging cycles are observed using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Was done.

FIG. 9A shows the discharge capacity value of each of the three cells as a function of the number of charge / discharge cycles. Each cell was designed to have an initial cell capacity of 100 mAh for ease of comparison. It is clear that the Li-S cells characterized by the HA junction current collectors of the present invention on both the anode side and the cathode side exhibit the most stable cycle behavior and suffer a capacity loss of 6% after 50 cycles. Cells with GO / resin coated Cu and GO coated Al current collectors experience a 23% volume reduction after 50 cycles. A cell with a Cu foil anode current collector and an Al foil cathode current collector will experience a 26% volume reduction after 50 cycles. Post-cycle inspection of the cell shows that the Al foil in all prior art electrodes suffers from severe corrosion problems. In contrast, the humate oxide-bonded Al current collectors of the present invention remain intact.

FIG. 9B shows a ragone plot (mass output density vs. mass energy density) of the three cells. Surprisingly, our HA-bonded metal foil current collectors are graphene / resin-coated current collectors on the anode side (using GO-coated Al foil on the cathode side), and Cu / Al. Note that it provides both higher energy densities and higher output output densities for Li-S cells compared to collectors. It is quite unexpected that Cu foil has an electrical conductivity that is more than an order of magnitude higher than the electrical conductivity of graphene and HA films.

Example 12: For the preparation of _{a magnesium ion cell cathode active material (magnesium manganese silicate, Mg 1.03} Mn _0.97 SiO ₄ ) containing a current collector enabled by HA on the anode and cathode sides. , Reagent brand KCl (melting point = 780 ° C.) was used as a melt after drying under vacuum at 150 ° C. for 3 hours. The starting materials were magnesium oxide (MgO), manganese (II) carbonate (MnCO ₃ ) and silicon dioxide (SiO ₂ , 15-20 nm) powder. The theoretical amount of the precursor compound was controlled with a molar ratio of 1.03: 0.97: 1 for Mg: Mn: Si. The mixture (flux / reactant molar ratio = 4) was manually ground with a pestle in a mortar for 10 minutes and then poured into a corundum crucible. The powder mixture was then dried in vacuo for 5 hours at 120 ° C. to minimize the water content in the mixture. The mixture was then immediately transferred to a tube furnace and heated in a reducing atmosphere (Ar + 5 wt% H2) at 350 ° C. for 2 hours to remove carbonate groups. After this, final firing was performed at various temperatures at a rate of 2 ° C./min for 6 hours and then naturally cooled to room temperature. Finally, the product (magnesium manganese silicate, Mg _1.03 Mn _0.97 SiO ₄ ) was washed 3 times with deionized water to dissolve all remaining salts and separated by centrifugation for 2 hours. It was dried under vacuum at 100 ° C. for a while.

The electrodes (either anode or cathode) are typically 85 wt% electrode active material (eg Mg _1.03 Mn _0.97 SiO ₄ particles, 7 wt% acetylene black (Super-P), and 8 wt% polyfluoridene fluoride. It was prepared by mixing a vinylidene fluoride binder (PVDF dissolved in N-methyl-2-pyrrolidinoe (NMP), 5 wt% solid content) to form a slurry mixture. After coating the slurry on the current collector, the resulting electrodes were dried in vacuum at 120 ° C. for 2 hours to remove the solvent before pressurization. Three cells with different current collectors. Investigated: First cell having HA-bonded Cu foil and HA-bonded Al foil as anode current collector and cathode current collector, respectively; GO / resin coated Cu foil as anode current collector and cathode current collector and Second cell with GO coated Al foil (without pre-etching) (predecessor cell); third cell with Cu foil anode current collector and Al foil cathode current collector (predecessor cell) ).

Then, the electrode was cut into a disk (diameter = 12 mm) for use as a cathode. A thin sheet of magnesium foil was attached to the surface of the anode current collector, and then a porous separator (eg, Celgard 2400 membrane) was stacked on top of the magnesium foil. A single cathode disk coated on a cathode current collector was used as a cathode and stacked on a separator layer to form a CR2032 coin-shaped cell. The electrolyte used was 1M Mg (AlCl ₂ EtBu) ₂ in THF. The cell assembly was performed in an argon-filled glove box. CV measurements were performed using a CHI-6 electrochemical workstation at a scanning rate of 1 mV / s. Also, the electrochemical performance of the cells is constant current charging with a current density of 50mA / g-10A / g (up to 100A / g for some cells) using Arbin and / or LAND electrochemical workstations. / Evaluated by the progress of the discharge cycle.

FIG. 10 shows the cell discharge specific volume value of each of the three cells as a function of the number of charge / discharge cycles. It is clear that the Mg ion cells characterized by the current collectors of the present invention on both the anode side and the cathode side exhibit the most stable cycle behavior and suffer a capacity loss of 2.5% after 25 cycles. A cell with a GO / resin coated Cu foil current collector and a GO coated Al foil current collector will experience a 17% volume reduction after 25 cycles. A cell with a Cu foil anode current collector and an Al foil cathode current collector will experience a 30% volume reduction after 25 cycles. Post-cycle inspection of the cell showed that the GO / resin coated Cu foil collector and the GO coated Al foil collector were swollen, showing some delamination from the cathode layer, and Al foil shows that it suffers from severe corrosion problems. In contrast, the HA-bonded metal foil current collectors of the present invention remain intact.

Example 13: Chemical and mechanical compatibility tests of various current collectors for various intended batteries or supercapacitors As demonstrated in Examples 11 and 12 above, the electrolyte of the battery or supercapacitor. On the other hand, the long-term stability of the current collector is a major problem. To understand the chemical stability of the various current collectors, we have begun the main task of exposing the current collectors to some typical electrolytes. After an extended period of time (eg, 30 days), the current collector was removed from the electrolyte solution and observed using optical and scanning electron microscopy (SEM). A list of results is given in Table 3 below, where the HA-bonded metal foil current collectors of the present invention are highly compatible with all types of liquid electrolytes commonly used in batteries and supercapacitors. Consistently demonstrate that you are. The materials of the present invention are resistant to any chemical attack. These HA-protected current collectors are essentially electrochemically inert over the voltage range of 0-5.5 volts with respect to ^{Li / Li + and are intended for use with almost any battery / capacitor electrolyte.} Are suitable.

It may be pointed out that each current collector must be connected to a tab and then to an external circuit line. The current collector must be mechanically compatible with the tab and must be quickly or easily fixed or joined to it. We have found that whenever a CVD graphene film is mechanically simply fixed to a tab, it breaks or bursts easily. Even with the help of adhesive, the CVD film is easily torn during the procedure of connecting to the tab or battery cell packaging.

In conclusion, we have successfully developed a thin film derived from humic acid bonded on the surface of a metal foil: an absolutely new, novel, unexpected, clearly distinguishable class of highly conductive materials. The chemical composition, structure (crystal completion, crystal grain size, defect group, etc.), crystal orientation, morphology, manufacturing method, and properties of this new class of materials include flexible graphite foil, polymer-derived pyrolytic graphite, and CVD-derived PG. Besides (such as HOPG), it is fundamentally different and clearly distinguished from the catalytic CVD graphene thin film that is self-supporting or coated on a metal foil. The thermal conductivity, electrical conductivity, scratch resistance, surface hardness, and tensile strength exhibited by the materials of the present invention are determined by prior art flexible graphite sheets, discrete graphene / GO / RGO platelit paper, or. Higher than what other graphite films can probably achieve. These HA-derived thin film structures have the best combination of excellent electrical conductivity, thermal conductivity, mechanical strength, surface scratch resistance, hardness, and no tendency to peel off.

Claims (53)

A humic acid-bonded metal foil current collector for use in a battery or a supercapacitor .
(A) A thin metal foil having a thickness of 1 μm to 30 μm and two opposite, substantially parallel primary surfaces.
(B) at least one thin film or highly conductive graphite film obtained therefrom of a mixture of humic acid (HA) or HA and graphene sheet, said thin film or the graphite film of HA or HA / graphene mixture , At least one thin film of fumic acid (HA) or a mixture of HA and graphene sheet, or a highly conductive graphite film obtained from it, which is chemically bonded to at least one of the two opposing primary surfaces of the metal foil. viewing including the door,
Wherein the HA or HA / graphene mixture thin film or the graphite film, the thickness of 5 nm to 10 m, an oxygen content of 0.01 wt% to 10 wt%, the physical of 1.3~2.2g / cm ³ Density, hexagonal carbon planes oriented substantially parallel to each other and parallel to the primary surface, interplanetary spacing of 0.335 to 0.50 nm between hexagonal carbon planes, measured alone without the thin metal foil. A fumic acid-bonded metal foil current collector characterized by having a thermal conductivity greater than 250 W / mK and an electric conductivity greater than 800 S / cm. The current collector according to claim 1, wherein each of the two opposing primary surfaces is chemically bonded to the thin film of humic acid or an HA / graphene mixture or the highly conductive graphite film. Electric body. In the current collector according to claim 1, the thin film of HA or HA / graphene or the graphite film is at least one of the two opposing primary surfaces of the metal foil without the use of a binder or adhesive. A current collector characterized by being chemically bonded together. In the current collector according to claim 1, the thin film of HA or HA / graphene or the graphite film is at least one of the two opposing primary surfaces of the metal foil using a binder or adhesive. A current collector characterized by being joined to. The current collector according to claim 4, wherein the binder or adhesive is an electrically conductive material selected from essentially conductive polymers, pitches, amorphous carbons, or carbonized resins. A current collector. The current collector according to claim 1, wherein the thin metal foil has a thickness of 4 to 12 μm, and the thin film of a humic acid or HA / graphene mixture has a thickness of 20 nm to 2 μm. Collector. The current collector according to claim 1, wherein the at least one primary surface does not contain a layer of passivated metal oxide on the current collector. The current collector according to claim 1, wherein the metal foil is selected from Cu, Ti, Ni, stainless steel, Al foil, or a combination thereof. The current collector according to claim 1, wherein the thin film or graphite film has an oxygen content of 1% by weight to 5% by weight. In the current collector according to claim 1, the thin film or graphite film has an oxygen content of less than 1%, an inter-plane spacing of less than 0.345 nm, and an electric conductivity of 3,000 S / cm or more. A current collector characterized by. In the current collector according to claim 1, the thin film or graphite film has an oxygen content of less than 0.1%, an interplanetary spacing of less than 0.337 nm, and an electrical conductivity of 5,000 S / cm or more. A current collector characterized by having. In the current collector according to claim 1, the thin film or graphite film has an oxygen content of 0.05% or less, a surface spacing of less than 0.336 nm, a mosaic spread value of 0.7 or less, and 8,000 S. A current collector characterized by having an electrical conductivity of / cm or more. In the current collector according to claim 1, the thin film or graphite film has an interplane spacing of less than 0.336 nm, a mosaic spread value of 0.4 or less, and an electrical conductivity of greater than 10,000 S / cm. A current collector characterized by that. The current collector according to claim 1, wherein the graphite film exhibits a surface spacing of less than 0.337 nm and a mosaic spread value of less than 1.0. The current collector according to claim 1, wherein the graphite film exhibits a graphitization degree of 80% or more and / or a mosaic spread value of 0.4 or less. In the current collector according to claim 1, the thin film deposits a suspension of HA or a mixture of HA and a graphene sheet on the at least one primary surface under the influence of orientation control stress. A current collector obtained by forming a layer of HA or a mixture of HA and a graphene sheet, and then heat-treating the layer at a heat treatment temperature of 80 ° C. to 1,500 ° C. The current collector according to claim 16, wherein the heat treatment temperature is 80 ° C. to 500 ° C. The current collector according to claim 16, wherein the heat treatment temperature is 80 ° C. to 200 ° C. The current collector according to claim 1, wherein the thin film contains chemically bonded humic acid molecules or chemically assimilated humic acid and graphene surfaces parallel to each other. The current collector according to claim 1, wherein the thin film is a continuous length film having a length of 5 cm or more and a width of 1 cm or more. In the current collector according to claim 1, the thin film or graphite film has a ^{physical density greater than 1.6 g / cm 3} and / or a tensile strength greater than 30 MPa when measured alone. A current collector characterized by. In the current collector according to claim 1, the thin film or graphite film has a ^{physical density greater than 1.8 g / cm 3} and / or a tensile strength greater than 50 MPa when measured alone. A current collector characterized by. In the current collector according to claim 1, the thin film or graphite film has a ^{physical density greater than 2.0 g / cm 3} and / or a tensile strength greater than 80 MPa when measured alone. A current collector characterized by. A rechargeable lithium battery or lithium ion battery comprising the current collector according to claim 1 as an anode current collector and / or a cathode current collector. In a rechargeable lithium battery containing the current collector according to claim 1 as an anode current collector or a cathode current collector, a lithium-sulfur cell, a lithium-sulene cell, a lithium sulfur / selenium cell, a lithium-air cell, a lithium-sulfur battery. A rechargeable lithium battery characterized by being a graphene cell, or lithium-carbon cell. The capacitor containing the current collector according to claim 1 as an anode current collector or a cathode current collector is a symmetric ultracapacitor, an asymmetric ultracapacitor cell, a hybrid supercapacitor-capacitor cell, or a lithium ion capacitor cell. Characteristic capacitors. A method for manufacturing a highly-oriented humic acid film bonding metal foil current collector for use in a battery or a supercapacitor, the method comprising
(A) In the step of preparing a dispersion of humic acid (HA) or chemically functionalized humic acid (CHA) sheet dispersed in a liquid medium, the HA sheet has an oxygen content higher than 5% by weight. Or the CHA sheet containing a non-carbon element content higher than 5% by weight.
(B) In the step of distributing and depositing the HA or CHA dispersion on at least one primary surface of a metal foil to form a wet layer of HA or CHA, the distribution and deposition procedure orient-induced stresses on the dispersion. And the process including the process to be used for
(C) The liquid medium is partially or completely removed from the wet layer of HA or CHA and has an _{interplane spacing d 002 of 0.4 nm to 1.3 nm as measured by hexagonal carbon planes and X-ray diffraction.} The process of forming a dried HA or CHA layer and
(D) A step of heat-treating the dried HA or CHA layer at a first heat treatment temperature higher than 80 ° C. for a sufficient time to produce the highly oriented fumic acid film bonded metal foil current collector. , highly oriented humic acid film, containing at least one is chemically bonded to and parallel to the primary surface interconnected, HA or CHA sheets assimilated or thermal reduction with substantially parallel to each other, before Symbol height how to oriented humic acid film, 1.3 g / cm ³ or more physical density, characterized in that it comprises a step of at least 250 W / mK in thermal conductivity, and / or 500S / cm or more electrical conductivity .. In the method according to claim 27, the second heat treatment temperature at which the highly oriented fumic acid film bonded metal foil is higher than the first heat treatment temperature for a sufficient time for producing the graphite film bonded metal foil current collector. further comprising the steps of heat-treating (e) in a step of the graphite film has an oxygen content or non-carbon element content of spacing d ₀₀₂ and less than 5 wt% between the faces of less than 0.4 nm, prior Symbol graphite film To produce a highly conductive graphite film having a physical density of 1.3 g / cm ³ or more, a thermal conductivity of at least 500 W / mK, and / or an electrical conductivity of 1,000 S / cm or more. (f) the way further comprising a. The method of claim 27, wherein the after step (d), how you further comprising the step of compressing the high orientation humic acid film of assimilation or reduced HA or CHA. The method of claim 27, wherein the HA or CHA dispersion, the graphene sheet or molecules dispersed therein further comprises, H A pair graphene or CHA-to graphene weight ratio of 1/100 to 100/1 The graphene is pure graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene bromide, graphene iodide, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, or theirs. A method characterized by being selected from a combination of. In the method of claim 30, the assimilated or reduced HA or CHA highly oriented humic acid film is coated with an interplanetary spacing of less than 0.4 nm d ₀₀₂ and an oxygen content or non-carbon element content of less than 5% by weight. In the step (e) of further heat treatment at a second heat treatment temperature higher than the first heat treatment temperature for a sufficient time for producing a graphite film having the above, the graphite film is compressed to 1.6 g / cm. ^{It is characterized by further comprising the step (f) of producing a highly conductive graphite film having a physical density of 3} or more, a thermal conductivity of at least 700 W / mK, and / or an electric conductivity of 1,500 S / cm or more. who shall be the method. The method according to claim 27, wherein the HA or CHA sheet is in an amount sufficient to form a liquid crystal phase in the liquid medium. In the method of claim 27, the first volume fraction of HA or CHA in which the dispersion is dispersed in the liquid medium that exceeds _{the critical volume fraction (V c} ) for the formation of the liquid crystal phase. A method comprising and enriching the dispersion to reach a second volume fraction of HA or CHA greater than the first volume fraction and improving the orientation of the HA or CHA sheet. 33. The method of claim 33, wherein the first volume fraction is equal to a weight fraction of 0.05% to 3.0% by weight of HA or CHA in the dispersion. .. In the method of claim 34, the dispersion is concentrated prior to step (b) and contains more than 3.0% by weight and less than 15% by weight of HA or CHA dispersed in the liquid medium. A method characterized by. The method of claim 27, wherein the dispersion further contains a polymer that is dissolved in the liquid medium or adhered to the HA or CHA. In the method of claim 27, the CHA is a polymer, SO ₃ H, COOH, NH ₂ , OH, R'CHOH, CHO, CN, COCl, aryl, COSH, SH, COOR', SR', SiR'. _{3, Si (- OR '-} ) y R' 3-y, Si (- O - SiR '2 -) OR', R '', Li, AlR '2, Hg - X, TlZ ₂ and Mg-X (in the formula, y is an integer less than or equal to 3 and R'is hydrogen, alkyl, aryl, cycloalkyl, or aralkyl, cycloaryl, or poly (alkyl ether), where R'' is. Contains a chemical functional group selected from (fluoroalkyl, fluoroaryl, fluorocycloalkyl, fluoroaralkyl or cycloaryl, where X is a halide, Z is a carboxylate or trifluoroacetate, or a combination thereof). A method characterized by that. In the method according to claim 30, the graphene sheet is a polymer, SO ₃ H, COOH, NH ₂ , OH, R'CHOH, CHO, CN, COCl, aryl, COSH, SH, COOR', SR', SiR. _{'3, Si (- OR'} -) y R '3-y, Si (- O - SiR' 2 -) OR ', R'', Li, AlR' 2, Hg - X, TlZ ₂ and Mg --X (in the formula, y is an integer less than or equal to 3 and R'is hydrogen, alkyl, aryl, cycloalkyl, or aralkyl, cycloaryl, or poly (alkyl ether), R'' Is a fluoroalkyl, fluoroaryl, fluorocycloalkyl, fluoroaralkyl or cycloaryl, X is an arylide, Z is a carboxylate or trifluoroacetate, or a combination thereof). A method characterized by containing chemically functionalized graphene. In the method of claim 28, the second heat treatment temperature _{reduces the interplanetary spacing d 002} to a value less than 0.36 nm, and reduces the oxygen content or non-carbon element content by 0.1 weight. A method characterized by being above 1,500 ° C. for a sufficient amount of time to reduce to less than%. The method according to claim 27, wherein the liquid medium comprises water or a mixture of water and alcohol. In the method according to claim 27, the liquid medium is polyethylene glycol, ethylene glycol, propylene glycol, alcohol, sugar alcohol, polyglycerol, glycol ether, amine solvent, amide solvent, alkylene carbonate, organic acid, or inorganic. A method characterized by containing a non-aqueous solvent selected from acids. In the method according to claim 27, which is a roll-to-roll method, the step (b) is a step of supplying the sheet of the metal foil from the roller to the deposition region and a layer of the HA or CHA dispersion is a metal foil. To form the wet layer of HA or CHA dispersion on at least one primary surface of the sheet, and to dry the HA or CHA dispersion and deposit on the surface of the metal foil. A method comprising a step of forming a dried HA or CHA layer and a step of collecting the HA or CHA layer deposited metal foil sheet on a collector roller. In the method according to claim 27, the first heat treatment temperature includes a temperature in the range of 100 ° C. to 1,500 ° C., and the highly oriented humic acid film has an oxygen content of less than 2.0%, 0.35 nm. A method characterized by having an interplanar spacing of less ^{than, a physical density of 1.6 g / cm 3} or greater, a thermal conductivity of at least 800 W / mK, and / or an electrical conductivity of 2,500 S / cm or greater. In the method of claim 27, the first heat treatment temperature comprises a temperature in the range of 1,500 ° C. to 2,100 ° C., and the highly oriented humic acid film has an oxygen content of less than 1.0%, 0. A method characterized by having an interplane spacing of less than 345 nm, a thermal conductivity of at least 1,000 W / mK, and / or an electrical conductivity of 5,000 S / cm or more. In the method according to claim 28, the first and / or second heat treatment temperature includes a temperature of more than 2,100 ° C., and the highly conductive graphite film has an oxygen content of 0.1% or less, 0. A method characterized by having an inter-graphene spacing of less than 340 nm, a mosaic spread value of 0.7 or less, a thermal conductivity of at least 1,300 W / mK, and / or an electrical conductivity of 8,000 S / cm or more. In the method according to claim 28, the second heat treatment temperature includes a temperature of 2,500 ° C. or higher, the highly conductive graphite film has an inter-graphene spacing of less than 0.336 nm, and a mosaic spread value of 0.4 or less. , A method characterized by having a thermal conductivity greater than 1,500 W / mK and / or an electrical conductivity greater than 10,000 S / cm. The method according to claim 28, wherein the highly conductive graphite film exhibits a graphitization degree of 80% or more and / or a mosaic spread value of less than 0.4. The method according to claim 27, wherein the HA or CHA sheet has a maximum original length, and the highly oriented humic acid film contains an HA or CHA sheet having a length larger than the maximum original length. how to. The method of claim 28, wherein said high-conductivity graphite film, characterized in that a polycrystalline graphene structure having a preferred crystal orientation during Hence measuring the X-ray diffraction. In the method according to claim 28 or 31 , in the step (e) of the heat treatment, the HA or CHA sheet is chemically linked, assimilated, or chemically bonded to another HA or CHA sheet or a graphene sheet to form a graphite structure. A method comprising the steps of forming. In the method of claim 28, the highly conductive graphite film has an electrical conductivity greater than 5,000 S / cm, a thermal conductivity greater than 800 W / mK, a ^{physical density greater than 1.9 g / cm 3, and a} physical density of 80 MPa. A method characterized by having a greater tensile strength and / or a modulus of elasticity greater than 60 GPa. In the method of claim 28, the highly conductive graphite film has an electrical conductivity greater than 8,000 S / cm, a thermal conductivity greater than 1,200 W / mK, and a physical density greater than ^{2.0 g / cm 3.} , A method characterized by having a tensile strength greater than 100 MPa and / or an elastic modulus greater than 80 GPa. In the method of claim 28, the highly conductive graphite film has an electrical conductivity greater than 12,000 S / cm, a thermal conductivity greater than 1,500 W / mK, and a physical density greater than ^{2.1 g / cm 3.} A method characterized by having a tensile strength greater than 120 MPa and / or an elastic modulus greater than 120 GPa.

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