JP2015527707A - Graphene coated electrode - Google Patents

Abstract

Electrode for coating graphene United States Patent Application 20070249405 Kind Code: A1 An object of the present invention is to have a first electrode containing a plurality of lithium particles, and at least partially coat a carbon layer on the surface of each particle, It is an object of the present invention to provide a battery containing graphene by electrochemical stripping that covers the plurality of particles. The battery includes a second electrode and an electrolyte, and at least a portion of the first electrode and at least a portion of the second electrode are in contact with the electrolyte. [Selection] Figure 11

Description

  The present invention relates to a lithium battery.

  Lithium ion batteries have high capacity and good electrochemical performance, and are applied to a wide range of energy storage facilities such as solar energy, wind energy, hydroelectric power generation, and electric vehicles. By improving the speed capability and energy density of lithium ion batteries, it is possible to meet the demand for higher capacity storage. For example, by enhancing the electrochemical performance of a lithium ion battery having lithium iron phosphate as the positive electrode, coating the positive electrode with carbon enables both metal doping and / or small particle formation.

(Cross-reference of related applications)
This application includes Taiwan provisional patent application No. 101126393 filed on July 20, 2012, and Chinese provisional patent application No. 201210254448. filed on July 20, 2012. X and related applications of US Provisional Patent Application No. 13 / 800,096 filed on March 13, 2013 and claim priority based on this related application.

US Provisional Patent Application No. 13 / 170,624 Taiwan provisional patent application No. 100115655

  In the battery disclosed in the present invention, amorphous carbon-coated lithium iron phosphate is incorporated as an electrode material. For example, when negative electrode material or positive electrode material contains graphene by electrochemical peeling, an obvious polarization voltage is generated. Without realizing high specific discharge, high energy density, and high output. Such cells also showed low capacity irreversible loss and extended cycle life in the first cycle.

  In general, a battery includes a first electrode containing a plurality of lithium particles, the surface of each particle being at least partially coated with a carbon layer, and at least partially having one or more particles. The graphene by electrochemical exfoliation coated with is included. The battery includes a second electrode and an electrolytic solution. Further, at least a part of the first electrode and at least a part of the second electrode are in contact with the electrolytic solution.

  In order to achieve the object of the battery disclosed in the present invention, one or more items described below may be included. First, the first electrode is a positive electrode or a negative electrode. The battery can be a button-type battery, a cylindrical battery, or a pouch-type electrical ground. The particles include lithium iron phosphate, lithium iron composite oxide, lithium iron phosphate composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt manganese nickel composite or lithium cobalt manganese. Nickel composite oxide is included. The graphene by electrochemical stripping includes graphene by electrochemical stripping including a flake formed on carbon. The amount of graphene by electrochemical stripping is about 0.001 wt% to about 5 wt% with respect to the electrode.

  In general, the electrode material includes a plurality of particles containing lithium. The surface of each particle is coated with carbon at least partially, and includes graphene by electrochemical stripping in which at least a portion is coated with one or more large amounts of particles.

  In order to achieve the purpose of the electrode material, one or more embodiments described below are included. The particles include lithium iron phosphate, lithium iron composite oxide, iron lithium phosphate composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt manganese nickel composite or lithium cobalt. Manganese nickel composite oxide is included. The carbon layer includes amorphous carbon. Graphene by electrochemical stripping includes graphene by electrochemical stripping of flakes formed on carbon. The amount of graphene by electrochemical stripping is about 0.001 wt% to about 5 wt% with respect to the electrode material. The specific volume of electrode material is at least about 180 mAh / g and can be about 210 mAh / g. The oxygen contained in graphene by electrochemical stripping is about 20 wt% or less. The magnetic permeability of graphene by electrochemical peeling is about 90% or less, and the flake resistance is about 10 kΩ / sq or less. The electrode material includes a conductive additive, a binder, a carbon material, or an additional substance containing a solvent. In some specific embodiments, the carbon material includes graphene, soft carbon, hard carbon, carbon nanotubes, or carbon fibers. The electrode material includes sulfur, silicon, tin, a ceramic material, or lithium sulfide. The electrode material includes a transition metal dichalcogenide. The electrode material includes triazine or thiophene. The electrode material may be a positive electrode material or a negative electrode material.

  In general, in the electrode material manufacturing method, a plurality of lithium-containing particles and the surface of each particle are at least partially coated with carbon, and graphene is formed between the plurality of particles by electrochemical peeling. To provide that. One or more particles are coated on at least a part of graphene by electrochemical stripping.

  Implementation of the fabrication methods disclosed in the present invention includes one or more embodiments described below. The particles include lithium iron phosphate, lithium iron composite oxide, lithium iron phosphate composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt manganese nickel composite or lithium cobalt manganese. Nickel composite oxide is included. The carbon layer includes an amorphous carbon layer. The graphene formed by electrochemical exfoliation formed between a plurality of particles includes mechanically mixed particles and graphene produced by electrochemical exfoliation. A plurality of particles having a graphene by electrochemical or exfoliation are doped either manually or chemically. The manufacturing method includes the formation of graphene by electrochemical stripping. In some specific embodiments, to form graphene by electrochemical stripping, a first electrode containing a first carbon material and a second electrode are immersed in a solution containing an electrolyte, Generating a potential between the first and second electrodes is included.

  The fabrication methods disclosed in the present invention have one or more advantages. Fabrication of amorphous carbon-coated lithium iron phosphate electrodes containing graphene by electrochemical stripping is very simple, scaleable, and compatible with conventional processing methods and materials. Furthermore, it is possible to improve the performance of a lithium ion battery having an amorphous carbon-coated lithium iron phosphate electrode containing graphene by electrochemical stripping only by using a small amount of graphene by electrochemical stripping.

  In order to make the matters, features, and advantages disclosed in the present invention easier to understand, the following description will be given with reference to the drawings.

It is a figure which shows the experimental apparatus which comprises the graphene by the electrochemical peeling disclosed in this invention. It is a flowchart which shows comprising the graphene by the electrochemical peeling disclosed in this invention. 3 shows image data obtained by photographing a graphene flake by electrochemical peeling disclosed in the present invention using an optical microscope, a scanning electron microscope, or an atomic force microscope. 3 shows image data obtained by photographing a graphene flake by electrochemical peeling disclosed in the present invention using an optical microscope, a scanning electron microscope, or an atomic force microscope. 3 shows image data obtained by photographing a graphene flake by electrochemical peeling disclosed in the present invention using an optical microscope, a scanning electron microscope, or an atomic force microscope. It is the statistical figure which measured the thickness of the graphene flake by the electrochemical peeling disclosed in this invention. It is a Raman spectrum and X-ray spectrum of a graphene flake by the electrochemical peeling disclosed in the present invention. It is a Raman spectrum and X-ray spectrum of a graphene flake by the electrochemical peeling disclosed in the present invention. It is an electrode figure containing the graphene by the electrochemical peeling disclosed in the present invention. It is a flowchart regarding the electrode preparation process disclosed in this invention. It is a spray-drying process diagram disclosed in the present invention. It is scanning electron micrograph image data of the lithium iron phosphate particle wrapped in the graphene by the electrochemical peeling disclosed in the present invention. It is scanning electron micrograph image data of the lithium iron phosphate particle wrapped in the graphene by the electrochemical peeling disclosed in the present invention. It is a figure which shows embodiment of the electrochemical cell disclosed in this invention. It is a figure which shows embodiment of the button type battery disclosed in this invention. It is a figure which shows embodiment of the cylindrical battery disclosed in this invention. It is a figure which shows embodiment of the pouch-type battery disclosed in this invention. It is a figure which shows the characteristic regarding the charging / discharging of the electrochemical cell which has the iron phosphate re-positive electrode enclosed with the graphene by the electrochemical peeling disclosed in this invention. It is a figure which shows the characteristic regarding the charging / discharging of the electrochemical cell which has the iron phosphate re-positive electrode enclosed with the graphene by the electrochemical peeling disclosed in this invention. It is a figure which shows the lithium iron phosphate particle | grains encapsulated with the graphene by the electrochemical peeling disclosed in this invention. It is a transmission electron micrograph image data after charging the lithium iron phosphate material wrapped in the graphene by the electrochemical peeling disclosed in the present invention. It is a transmission electron micrograph image data after discharging the lithium iron phosphate material wrapped in the graphene by the electrochemical peeling disclosed in the present invention. It is a transmission electron micrograph image data after discharging the lithium iron phosphate material wrapped in the graphene by the electrochemical peeling disclosed in the present invention. It is a transmission electron micrograph image data of the lithium iron phosphate material wrapped in the graphene by the electrochemical peeling disclosed in the present invention. It is a figure which shows the life cycle of a electrochemical cell which has a lithium iron phosphate positive electrode encapsulated with the graphene by the electrochemical peeling disclosed in this invention, and capacity | capacitance. It is a figure which shows the charging / discharging characteristic of the electrochemical cell which has the amorphous carbon covering lithium iron phosphate positive electrode enclosed with the graphene disclosed in this invention. It is a figure which shows the discharge capacity and Coulomb efficiency regarding the electrochemical cell which has a lithium iron phosphate positive electrode encapsulated with the graphene by the electrochemical peeling disclosed in this invention. It is a figure which shows the relationship between the capacity | capacitance retention rate and discharge rate of the electrochemical cell which has a lithium iron phosphate negative electrode wrapped with the graphene by the electrochemical peeling disclosed in this invention. It is a figure which shows the life cycle and capacity | capacitance relationship of the electrochemical cell which has a lithium iron phosphate negative electrode encapsulated with the graphene by the electrochemical peeling disclosed in this invention. It is a figure which shows the 2nd cycle voltage profile of the positive electrode disclosed in this invention. It is a figure which shows the relationship between the specific amount of each positive electrode disclosed in this invention, and a charge cycle. It is a figure which shows the relationship of the cyclic voltamentary (CV) of the silica particle enclosed with the graphene by the electrochemical peeling disclosed in this invention. It is a figure which shows the composite positive electrode material disclosed in this invention. It is a figure which shows the positive electrode formed from the composite positive electrode material regarding FIG. 22A disclosed in this invention. It is a figure which shows the relationship between the specific spring amount and voltage regarding each composite positive electrode material disclosed in this invention.

  The present invention is a battery containing an amorphous carbon-coated lithium iron phosphate electrode, having a negative electrode or a positive electrode of graphene by electrochemical stripping, without producing a clear polarization voltage, high specific spring rate, high energy density, Achieve high output. For example, the negative electrode or the positive electrode is formed by particles encapsulated with graphene by electrochemical stripping containing lithium (that is, at least partially covered). Such cells also exhibited low capacity irreversible loss and extended cycle life in the first cycle.

(Graphene by electrochemical stripping)
In the present invention, for example, as described in Patent Document 1 filed on June 28, 2011 and Patent Document 2 filed on May 4, 2011, which are incorporated herein by reference, graphene Is immersed in an electrolyte solution and electrochemically exfoliated to produce a graphene flake by electrochemical exfoliation (herein, this is called graphene by electrochemical exfoliation). Also, by using electrochemical exfoliation, it is possible to produce graphene flakes by a large amount of electrochemical exfoliation, most of the produced flakes are only a few layers thick, and high quality crystal structure with low defect density And low resistance.

  As shown in FIGS. 1A and 1B, the working electrode 1 and the ground electrode 2 are immersed in an electrolyte 3 (10) in order to produce graphene by electrochemical stripping. For example, the working electrode can be made using graphene, and the ground electrode can be made from a metal such as platinum. A low bias voltage (for example, +2.5 V) flowing from the voltage source 4 is applied to the working electrode 1 (12) to generate ions in the electrolytic solution 3, and are inserted into the graphene structure as the working electrode. Then, a high bias voltage (for example, +10 V) flowing from the voltage source 4 is applied to the working electrode 1 (14) to separate the graphene in the working electrode 1, thereby producing a thin sheet of graphene. This is also called a graphene flake. The graphene flakes can be taken out by using filtration and / or centrifugation (16). Next, the present invention will be specifically described using embodiments. Through the use of physical or chemical doping, or mixing with nitrogen or other non-carbon elements, graphene flakes can be treated or modified by further electrochemical stripping. For example, P-type graphene production using nitric acid or hydrogen peroxide, or N-type graphene production using an amine compound is possible.

In the electrochemical stripping process in a specific embodiment, the working electrode is a graphene rod and the ground electrode is a platinum wire. SO ₄ ^2- water solution (2.4 g of 98% sulfur acid (H ₂ SO ₄ ) and 11 mL of 30% potassium hydroxide solution are added to 100 mL of deionized (DI) water to adjust the pH value of the solution to about 12). Used as electrolyte. A +2.5 V static bias voltage is applied to the working electrode for 5-10 minutes to wet the graphene rod and slowly insert SO ₄ ^2- ions between the graphene crystals. When a bias voltage of +2.5 V is applied, the graphene rod remains in the single body. Thereafter, a bias voltage of +10 V is applied. For example, when a bias voltage of +10 V is applied and about 30 minutes have elapsed, several mg of graphene can be produced, and graphene is peeled off using this. When a bias voltage of +10 V is applied, graphene can be rapidly separated into flakes and can be dispersed on the surface of the electrolyte solution. The exfoliated graphene flakes and related products are dispersed in a dimethylformamide (DMF) solution after filtration and collection. Unnecessary thick graphene particles are removed from the graphene solution in the centrifuged dimethylformamide solution. In a specific embodiment, by applying a high bias voltage to the working electrode and switching within a range of +10 V and −10 V, the peeled graphene layer suppressed oxidation by sulfuric acid.

  2A, 2B, and 2C show optical microscope image data, scanning electron microscope image data, and atomic force microscope (AFM) image data, respectively, which are specific embodiments of the graphene flakes 20 respectively. The horizontal size of the graphene flakes is several μm to several tens of μm.

  As shown in FIG. 3, the thickness of the graphene flakes measured using an atomic force microscope was about 1.5 to 4.2 nm, and the average thickness was about 2.5 nm. FIG. 30 shows atomic force microscope image data photographed using a Dimension-Icon (registered trademark) apparatus (Lowell, Mass.) Manufactured by Veeco.

As shown in FIG. 4A, it is a specific embodiment (473 nm laser irradiation) of the Raman spectrum 40 of the graphene flakes by electrochemical stripping, and shows the presence of Raman D-band and D′-band. FIG. 4B is a specific embodiment of graphene flake binding energy (C1s line) 42 by electrochemical delamination measured using X-ray photoelectron spectroscopy (XPS), corresponding to 286.4 eV (C—OH bond). ) And 287.8 eV (corresponding to the C═O bond) and 288.9 eV (corresponding to the O═C—OH bond), and the amount of binding energy of the C1s line is shown. From the Raman spectrum 40 and the binding energy curve 42, it was found that there was a partial defect in the graphene flakes by electrochemical delamination. This is considered to be caused by, for example, graphene being oxidized by sulfuric acid. However, when the Raman spectrum is near 2700 cm ^−1, there is a sharp 2Dband, and even if there is a defect, the graphene flakes have a good and high quality graphene crystal structure, and the quality is graphene oxidation It can be said that it is superior to a graphene structure composed of an object or a reduced graphene flake.

Raman spectral analysis was performed using a confocal Raman spectrometer (NT-MDT, Santa Clara, CA). The wavelength of the laser beam is 473 nm (2.63 eV), the spot diameter of the laser beam is about 0.5 μm, and the resolution of the spectrum obtained by the diffraction grating forming 600 grooves per 1 mm is 3 cm ⁻¹ . . Spectral resolution per cm ⁻¹ was obtained using a high-efficiency diffraction grating (forming 1800 grooves per mm), thereby obtaining a more detailed Raman band alignment. The Raman peak appearing at 520 cm ⁻¹ of silicon was used as a reference for wave number calibration.

  The oxygen content of graphene by electrochemical exfoliation is lower than other graphenes such as graphene by chemical exfoliation and graphene by mechanical exfoliation and graphene formed by reduction from graphene oxide. From this, it was found that graphene by electrochemical stripping has higher conductivity than other graphenes. For example, the oxygen content of the graphene flakes by electrochemical stripping described herein can be about 18% or less, about 16% or less, about 13% or less, or about 2% to about 18%, about 4% to about 16%, It was suppressed to about 20 wt% or less, such as about 6% to about 14%, or about 8% to about 12%. The magnetic permeability of graphene by electrochemical stripping is about 91%, 93%, 95%, 97%, or 99% or higher, possibly reaching about 90% or higher. By electrochemical stripping between about 1.5 nm and about 5 nm in thickness (eg, about 1.5 nm to about 3 nm, about 2 nm to about 4 nm, about 2.5 nm to about 4.5 nm, about 3 nm to about 5 nm) The thin layer electrical resistance of the graphene flakes is about 9 kΩ / sq or less, about 8 kΩ / sq or less, about 7 kΩ / sq or less, about 6 kΩ / sq or less, about 5 kΩ / sq or less, about 4 kΩ / sq or less, about 3 kΩ / sq or less It became less than about 10kΩ / sq

(Electrode composition and production)
As shown in FIG. 5, this is a specific embodiment of the composite electrode 50, an electrode material 52 (for example, electrode material particles), graphene 54 by electrochemical stripping inserted into the electrode material 52, a binder 58, And a conductive additive 59. The electrode 50 can be used as a negative electrode and / or a positive electrode of a battery, such as a lithium ion battery, and as shown in FIGS. 9B to 9D, the electrode 50 can be used as a button type battery and a cylindrical battery or a rectangular pouch. A battery is preferred.

In a specific embodiment, the electrode material 52 is a lithium-based material and can be used as a negative electrode and / or a positive electrode of a lithium ion battery. For example, electrode material or lithium iron composite oxide, lithium iron phosphate (LiFePO ₄ ), iron lithium phosphate composite oxide, lithium cobalt composite oxide (LiCoO ₂ ), lithium manganese composite oxide, (LiMn ₂ O ₄ ) And lithium-based materials (for example, LiFe _(1-x) M _{x )} used as precursors for electrode materials such as lithium nickel composite oxide (LiNiO ₂ ), lithium cobalt manganese nickel composite, or lithium cobalt manganese nickel composite oxide. P (1-x) O _{2 (2-x)} , 0 ≦ X <1). For example, the lithium-based material can be coated using a coating layer such as an amorphous carbon layer. Specific embodiments of the electrode material include lithium iron phosphate particles coated with amorphous carbon.

  The present invention will be specifically described with reference to examples. The electrode material 52 includes one or more carbon materials, ceramic village materials, silicon, tin, other metals, or metal oxides. Carbon materials include natural or artificial graphene, soft carbon, hard carbon, carbon nanotubes, or carbon fibers (eg, vapor grown carbon fibers).

  The composite electrode 50 also includes one or more conductive additives 59, binders 58, carbon materials, additive materials such as solvents. The conductive additive 59 includes one or more conductive carbon blacks (eg, Super P® carbon black, Timcal, Switzerland) and primary artificial graphite (eg, Timrex® KS 6 graphene, Timcal Or other conductive additives. The binder 58 includes one or more vinyl fluoride resins, carboxymethyl cellulose, styrene-butadiene copolymers, or other binders. Carbon materials function as one or more natural or artificial graphene, soft carbon, hard carbon, conductive carbon materials, carbon nanotubes, carbon fibers (eg, vapor grown carbon fibers), or other carbon materials Carbon material is included. The solvent may be one or more N-methylpyrrolidone, dimethyl phthalate, acetonitrile, alcohol, or other solvents.

  Usually, the ratio of the amount of graphene 54 by electrochemical stripping included in the composite electrode 50 to the total amount of the electrode 100 is very small. For example, the composite electrode 50 may be about 0.001 wt% to about 2 wt%, about 0.01 wt% to about 1 wt%, about 0.05 wt% to about 1.5 wt%, or about 0.03 wt% to about 1.2 wt%. Thus, there is only graphene 54 by electrochemical stripping of about 0.001 wt% to about 5 wt%. However, as described in detail below, even if the electrode used in the lithium ion battery contains a small amount of graphene by electrochemical stripping as described above, it can have good charge / discharge performance. .

  As shown in FIG. 6, in order to produce a composite electrode having a graphene negative electrode by electrochemical stripping or a graphene positive electrode by electrochemical stripping, graphene by electrochemical stripping and an electrode material or a precursor of electrode material (60) are combined. It is possible to make it. For example, it is possible to bond graphene and electrode material or precursor by electrochemical stripping using a machine with ultrasonic bonding or homogeneous mixing. Graphene by electrochemical exfoliation can also be used as an electrode material by mechanical mixing, solution mixing, drying, physical or chemical surface modification, physical or chemical mixing on the positive electrode surface or negative electrode surface, or both methods. Or it is preferable to couple | bond the said precursor.

  The graphene mixture and electrode material by electrochemical exfoliation is preferably dry particle formation (60) by methods such as hot air drying, spray drying, or filtration drying. Hot air drying includes evaporating the mixture and removing the solution in a drying chamber or on a heating plate, leaving a powder mixed with graphene and electrode material by electrochemical stripping. Spray drying includes ejecting a mixture of graphene and electrode material by electrochemical stripping from a nozzle by high speed separation. Filter drying includes suction filtration of a mixture of graphene and electrode material by electrochemical stripping to form a block, and then forming dry particles.

  Particles produced by dry particle formation of a graphene and electrode material mixture by electrochemical stripping include a binder and a conductive additive and / or solvent (ratio of about 8: 1: 1) and / or an additive. By mixing, a slurry (64) can be formed. The solids content of the slurry is about 40% to about 50%. The slurry can be coated on a copper foil current collector or an aluminum foil current collector and used as an electrode of a button type battery device for an electrochemical test (66). Other devices such as single cells and single or double batteries or AA batteries, automotive batteries and other batteries can similarly have one or more electrodes comprising graphene by electrochemical stripping.

  As shown in FIG. 7, the present invention will be specifically described according to an embodiment. In the method of producing the electrode by spray drying, the homogeneous solution 71 is produced by uniformly mixing the graphene and the electrode material or the precursor by electrochemical peeling in the homogenizer 70. Using the peristaltic pump 72, the uniform solution 71 is sent to the spray disc and the nozzle 74 rotating at high speed via the pipeline 76, and ejected while being centrifuged at high speed. It is possible to set the temperature of the nozzle 74 for each solvent of the homogeneous mixture. The present invention will be specifically described below with reference to embodiments. The temperature of the nozzle 74 is between about 100 ° C and about 200 ° C. The ejected material was dried to a powder using a heater 78 and collected in a powder collection chamber 79. In a situation where the inlet temperature is high, an electrode is formed from the powder through a particle formation process. Spray drying is a preferred method for mass production of electrode materials.

The present invention will be specifically described below with reference to embodiments. Wrapped with lithium iron phosphate (LiFePO ₄ ) particles coated with a slight amorphous carbon layer and graphene flakes by slight electrochemical stripping (in the present invention, an electrode using lithium iron phosphate wrapped with graphene by electrochemical stripping) Electrodes were formed from lithium iron phosphate (LiFePO ₄ ) particles. Phosphoric acid containing particles coated with an amorphous carbon layer (Tatung Fine Chemicals Co., procured from Taipei, Taiwan) of about 300 nm in diameter directly from a graphene flake solution by 250 ppm concentrated electrochemical exfoliation mixed in dimethylformamide. Injected into iron lithium powder. The mixture was stirred at a temperature of 180 ° C., and the graphene flakes obtained by electrochemical peeling were dispersed to evaporate the solvent.

  After solvent evaporation, the graphene flakes encapsulated the particles due to the intermolecular force of the lithium iron phosphate particles coated with graphene and amorphous carbon by electrochemical stripping. This enveloping action protected lithium iron phosphate particles and contributed to preventing aggregation and volume expansion.

  FIG. 8A and FIG. 8B show a state in which graphene flakes 80 obtained by electrochemical peeling are actually coated on the surfaces of amorphous carbon-coated lithium iron phosphate particles 82 in scanning electron microscope image data. It was also observed that wrinkles 84 were present in the graphene flakes 80 due to electrochemical peeling.

As shown in FIG. 9A, a specific embodiment of the electrochemical cell 90 includes a graphene-supported electrode by electrochemical stripping. The electrochemical cell 90 can be used for measuring electrochemical behavior composed of various electrodes. The electrochemical cell 90 includes a first electrode 92 made of graphene by electrochemical stripping containing lithium iron phosphate. The graphene-carrying first electrode 92 by electrochemical peeling is considered to be a negative electrode or a positive electrode. The electrochemical cell 90 similarly includes a second electrode 94 made of lithium. Electrode 92 and electrode 94 are immersed in an electrolyte solution 96 containing ions 98 such as Li ⁺ ions.

  As shown in FIGS. 9B to 9D, the graphene-supported electrode by electrochemical stripping is used as the negative electrode and / or positive electrode of the button-type battery 91, the cylindrical battery 93, or the square pouch-type battery 95, respectively. Is possible.

  An embodiment of the present invention, 10 wt% Super P® carbon black, is mixed with 10 wt% polyvinylidene fluoride in N-methylpyrrolidone, followed by the graphene-coated lithium iron phosphate by electrochemical stripping. 80% by weight of active material was added. The mixture is made using stainless balls in a planetary ball mill at 400 rpm. The resulting slurry is applied to an aluminum foil current collector and dried at a temperature of 110 ° C. for 4 hours. Thereafter, an electrochemical cell such as a coin-type battery or a button-type battery is placed in a glove box filled with argon. Graphene by electrochemical stripping containing lithium iron phosphate contained in the dried slurry is used as the first electrode 92 (eg, negative electrode or positive electrode), and the lithium foil is the second electrode 94 (eg, positive electrode or negative electrode). And used as a separator in combination with Celgard® 2600 separator or Celgard® polypropylene / polyethylene / polypropylene (PP / PE / PP) Trilayer separator (eg, obtained from Celgard, Charlotte, NC) It is done. The electrolyte solution contains 1 M lithium hexafluorophosphate in a mixture in which ethylmethyl carbonate, dimethyl carbonate, and vinyl carbonate are dissolved in a volume ratio of 1: 1: 1. A specific embodiment of the electrolyte solution is 1M hexafluorophosphoric acid in a mixture of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate (volume ratio 1: 1: 1 wt%) containing 1% vinyl carbonate. Includes lithium dissolved.

  As a control, a positive electrode and a negative electrode not carrying graphene by electrochemical stripping were prepared and similarly incorporated into an electrochemical cell. For example, the negative electrode composite is formed from 80 wt% amorphous carbon-coated lithium iron phosphate and 10 wt% binder and 10 wt% conductive additive. These components were uniformly dissolved in N-methylpyrrolidone for the purpose of obtaining a slurry having about 40% to 50% solids. The composite slurry is coated on an aluminum foil current collector, and is compressed and formed as an electrode battery for a button-type lithium ion battery. A positive electrode composite material that does not contain graphene by electrochemical peeling can be manufactured using a similar manufacturing method.

(Lithium iron phosphate cathode wrapped in graphene by electrochemical stripping)
Next, an electrochemical cell that is an embodiment of the present invention will be described. This battery has a lithium iron phosphate positive electrode encapsulated with graphene by electrochemical stripping, and the battery is characterized by the amount of graphene by electrochemical stripping in the positive electrode. A lithium ion battery carrying a lithium iron phosphate positive electrode encapsulated with graphene by electrochemical stripping has good charge performance, high discharge performance, and good cycle life. For example, the specific discharge reaches about 210 mAh / g and the energy density reaches 600 Wh / kg. This specific volume is about 170 mAh / g for a similar positive electrode that does not contain graphene by electrochemical stripping, and the specific volume of a similar positive electrode that does not contain graphene by electrochemical stripping is the standard specific volume It exceeds the theoretical maximum specific spring rate of about 120-160 mAh / g. Furthermore, the energy density exceeded about 500 Wh / kg, which is the standard energy density of a similar positive electrode without graphene by electrochemical stripping. Such high specific discharge and energy density values indicated that the electrochemical performance of the cathode composite material was enhanced by the presence of graphene by electrochemical delamination.

  As shown in FIG. 10A, this was encased in graphene by electrochemical stripping containing 0.8 wt% (curve 102), 1.2 wt% (curve 104), 2 wt% (curve 106) graphene by electrochemical stripping. It is the electrochemical cell which carries a lithium iron phosphate positive electrode, and is a curve regarding the charging / discharging voltage of the 1st charge cycle measured in the load factor of 0.1C. In addition, an electrochemical cell (curve 100) serving as a control for a lithium iron phosphate positive electrode containing no graphene by electrochemical peeling was also measured. As the amount of graphene due to electrochemical delamination in the positive electrode increased, the specific yield of the electrochemical cell also increased. For example, the specific yield of the positive electrode having graphene by 0.8 wt% electrochemical stripping was 187 mAh / g, and the specific yield of the positive electrode having graphene by 2 wt% electrochemical stripping was 210 mAh / g. The theoretical specific yield of amorphous carbon-coated lithium iron phosphate particles is 170 mAh / g. In a range where a voltage of about 2.0 V to about 3.8 V is applied and in a constant voltage state, the electrochemical cell is measured by the environmental temperature and charged under a constant voltage of 3.8 V until the current reaches 0.05C. did.

  In FIG. 10B, the charge / discharge voltage of an electrochemical cell carrying a lithium iron phosphate positive electrode encapsulated with graphene by electrochemical exfoliation including 0.13 wt% (curve 109) of graphene by electrochemical exfoliation was measured in the same state. A curve is shown. For comparison, an electrochemical cell (curve 108) carrying a lithium iron phosphate positive electrode containing no graphene by electrochemical peeling was also measured. There was no clear difference between the two curves, indicating an increase in graphene content (see FIG. 10A) due to electrochemical stripping. It is inferred that the improvement of the specific spring rate is probably induced by the minimum threshold amount of graphene due to electrochemical delamination contained in the positive electrode material. Therefore, it is considered that the positive electrode having graphene by electrochemical peeling below the minimum threshold amount does not show improved performance.

Without being bound to any particular theory, the feasibility of other Li ⁺ ion storage locations in graphene by electrochemical stripping is used to carry a positive electrode with inserted graphene flakes by several layers of electrochemical stripping The improvement of the specific spring capacity of the electrochemical cell will be described. The main capacity of the electrochemical cell depends on extraction of lithium ions from lithium iron phosphate particles (when charging) and insertion of lithium ions into lithium iron phosphate particles (when discharging). The process is represented by the chemical formula lithium FePO ₄ = FePO ₄ + Li ⁺ + e ⁻ .

One or two limiting processes are used to extract lithium ions from lithium iron phosphate particles having an ordered meteorite structure. The first limiting process is the limitation of grain boundary phase diffusion. Diffusion of lithium iron phosphate with lithium ions is affected by structural properties such as ion disorder, foreign phases, stacking faults and / or other structural properties. Interruption of lithium ion diffusion prevents the interfacial activity between the lithium iron phosphate (LiFePO ₄ ) phase and the iron phosphate (FePO ₄ ) phase, thereby potentially allowing lithium to be extracted and inserted in the negative or positive electrode material. Prevent involvement. The loss of available volume for the lithium ion intercalation can cause capacity loss. The second limiting process is the low electronic conductivity of lithium iron phosphate. Low electron mobility hinders rapid electron transfer and limits the rate of lithium extraction and insertion, causing capacity loss.

  Without being bound by any particular theory, the capacity enhancement of an electrochemical cell carrying graphene by electrochemical stripping on the negative electrode or the positive electrode can be different from the lithium ions provided by the graphene flakes by several layers of electrochemical stripping. Due to the existence of storage mechanism. FIG. 11 shows a potential lithium ion storage mechanism. For example, lithium ions 110 can be inserted into graphene flakes 112 by electrochemical stripping of several layers on the surface of amorphous carbon 114-coated lithium iron phosphate particles 116, such as between graphene flake layers. Similarly, lithium ions 118 adsorb carbon 114 on the surface of lithium iron phosphate particles. Furthermore, the reversible redox reaction between lithium and electrochemically exfoliated graphene helps to increase capacity.

  The storage mechanism of lithium iron phosphate materials encapsulated in graphene by electrochemical delamination from image data taken with a transmission electron microscope after charging (ie after lithium ion extraction) and after discharge (ie after lithium ion insertion) It can be seen that Immediately after charging or discharging, the electrochemical cell was opened and tested, and image data taken with a transmission electron microscope was obtained. The positive electrode was immersed and washed in an ethanol solution and dried in a glove box. The dried positive electrode material was scraped off from the aluminum foil, placed in an ethanol solution, subjected to ultrasonic decomposition, dropped on a copper grid, and an image was taken with a transmission electron microscope.

  FIG. 12A shows a lithium ion phosphate particle 120 encased in electrochemically exfoliated graphene having 0.8 wt% electrochemically exfoliated graphene (that is, after extraction of positive lithium from the positive electrode material) and then photographed with a transmission electron microscope. High resolution image data obtained is shown. An amorphous carbon coating layer 122 having a thickness of about 1 nm was coated on the lithium iron phosphate particles 120. Graphene 124 flakes by electrochemical peeling of several layers having a thickness of about 1.5 to 2 nm were formed on the amorphous carbon coating layer 122. The graphene flakes 124 are usually ordered and laminated on the surface of the lithium iron phosphate particles 120.

  FIG. 12B shows the lithium iron phosphate-like particles 125 encapsulated with the graphene by electrochemical stripping having graphene by 0.8 wt% electrochemical stripping (that is, after plus lithium is inserted into the positive electrode material), and photographed with a transmission electron microscope. High resolution image data obtained is shown. FIG. 12C shows high-resolution enlarged image data taken with a transmission electron microscope after charging the lithium iron phosphate particles 125 encapsulated with graphene by electrochemical peeling. This is a graphene flake 126 by several layers of randomly arranged electrochemical strips, and many layers are randomly arranged on the surface of the lithium iron phosphate particles 125.

The interlayer spacing of the graphene flakes 126 changes with charge / discharge by the positive electrode particles 125. The interlayer spacing of the graphene flakes 126 included in the positive electrode particles 125 during discharge according to an embodiment of the present invention is 0.372 nm. On the other hand, the interlayer spacing of the graphene flakes 124 contained in the positive electrode particles 120 during charging is only 0.34 nm. In another embodiment of the present invention, the interlayer spacing of the positive electrode particles 125 during discharge was 0.38 nm, and the interlayer spacing of the positive electrode particles 120 during charging was 0.31 nm. It should be noted that such interlayer values were determined by averaging the interlayer spacing of multiple parts (for example, at least 12 parts or at least 20 parts) of an image taken using a transmission electron microscope. The expected interlayer spacing for crystalline graphene with a complete structure and intercalated with Li ⁺ was 0.37 nm.

The difference in structure between the charged graphene flakes and the discharged graphene flakes is that Li ⁺ ions are taken into the graphene flakes by electrochemical peeling during positive electrode discharge, and the interplanar spacing (d-spacing) of the graphene flakes by electrochemical peeling increases. There is. In particular, it is possible to provide a skeleton that intercalates (inserts) Li ⁺ ions into the crystal lattice that are more suitable due to the apparent interplanar (ie, interlayer) spacing in graphene by electrochemical stripping.

As shown in FIG. 13, this is high-resolution image data taken using a transmission electron microscope, and is a view of the surface of the graphene flakes 130 formed by electrochemical peeling at the ends of the discharged positive electrode particles 132. A hexagonal structure 134 is present in the graphene flakes 130, and the presence of a hexagonal lattice in which Li ⁺ ions are intercalated (inserted) into the crystal structure of the graphene flakes 130 is shown. The layout diagram 136 shows a crystal structure that allows intercalation (insertion) of Li ⁺ ions into graphene. The positive electrode capacity was increased by the presence of Li ⁺ ions that intercalated (inserted).

Adhering Li ⁺ ions to the graphene surface by electrochemical peeling is also effective for raising the positive electrode capacity. In general, deposition of Li ⁺ ions on the surface affects the life cycle stability of the electrochemical cell. As shown in FIG. 14, the life cycle (curve 140) of the electrochemical cell having the lithium iron phosphate positive electrode material encapsulated with graphene by electrochemical exfoliation supporting 0.8 wt% electrochemical exfoliation of graphene is stable. We have shown that Li ⁺ ions attached to the graphene surface may not be able to control the surplus capacity of such electrochemical cells by a dominant mechanism.

The presence of graphene due to electrochemical stripping on the lithium iron phosphate positive electrode can reduce irreversible initial cycle loss in terms of capacity of the electrochemical cell. Next, FIG. 10A shows the actual irreversible capacity of the electrochemical cell for the graphene-supported positive electrode by electrochemical stripping of 0.8 wt% (curve 102) and the graphene-supported positive electrode by electrochemical stripping of 1.2 wt% (curve 104). Indicated that the loss was zero. Without being bound to any particular theory, this performance is attributed to being encased by several layers of graphene with a highly uniform and highly conductive coating around the amorphous carbon-coated lithium iron phosphate particles It is. This uniform graphene coating layer provides a path through which electrons move quickly during charge and discharge. Usually, the mobility of electrons in sp ² bonds (that is, the types of bonds present in graphene) is higher than the mobility of electrons in sp ³ bonds (that is, the types of bonds present in amorphous carbon). . Effective electron transfer through the graphene coating by electrochemical stripping diffuses electrons to the surface of the lithium iron phosphate particles during the charge / discharge cycle, thus improving kinetics and reversibility for lithium insertion and extraction.

The irreversible capacity of the positive electrode material carrying graphene (curve 106) by 2 wt% electrochemical stripping increases by 5%. This is comparable to the irreversible capacity in a positive electrode electrochemical cell carrying amorphous carbon-coated lithium iron phosphate without graphene by electrochemical stripping. Usually, the initial cycle loss percentage increases as the carbon content of the lithium iron phosphate cathode material increases. This is because Li ⁺ increases due to the diffusion path of the amorphous carbon layer.

  The peak voltage of the graphene (curve 106) -supported positive electrode material by electrochemical stripping of 2 wt% is maintained at 3.4 V, so that the graphene by electrochemical stripping is uniformly coated, so that almost no undesirable polarization action is caused. Shown not to cause. If the graphene by electrochemical exfoliation covering lithium iron phosphate particles is not uniform (lamination by graphene flakes by several layers of electrochemical exfoliation), the laminated flakes act like graphene particles rather than several layers of graphene flakes And cause additional voltage polarization. Additional voltage polarization occurs under graphene weight percent conditions due to relatively high electrochemical delamination. As a control experiment, lithium iron phosphate particles encapsulated with 2 wt% of graphene by electrochemical stripping were prepared by roughly mixing the graphene solution by electrochemical stripping, not by adding one drop at a time. Since the graphene layer is stacked in this manufacturing method, a slightly thick aggregate is formed using the π-π interaction. As shown in FIG. 15, the voltage curve (curve 150) when the battery having the positive electrode material formed by such a method was tested showed clear voltage polarization. Such control experiments have demonstrated that the properties of graphene flakes from several independent layers of electrochemical delamination contribute to the observation of low polarization and low initial cycle percentage loss.

FIG. 16 shows a positive electrode material carrying lithium iron phosphate encased in graphene by electrochemical exfoliation of 0.13 wt% (data point 162) and 1.2 wt% (data point 164) of electrochemical exfoliation. The discharge capacity (that is, specific spring rate) of an electrochemical cell containing a positive electrode material carrying lithium iron phosphate encapsulated with graphene by peeling is shown. As a control, an electrochemical cell having no graphene (data point 160) by electrochemical stripping on a positive electrode material having lithium iron phosphate was also tested. The specific spring rate was determined by each charge / discharge rate test. Normally, as the discharge rate increases, none of the tested cathode material compositions can maintain a high discharge current (eg, quickly intercalating Li ⁺ ) and the specific spring rate decreases. . The positive electrode supporting graphene by electrochemical stripping consistently exhibits a higher specific spring rate than a positive electrode material not supporting graphene by electrochemical stripping, and has a low target discharge rate (e.g., 0.1C-1.3C). ) At least about 23% capacity, and at high discharge rates (eg, 2.5C-28C) at least about 26% capacity. For example, an electrochemical cell supporting graphene by 1.2 wt% electrochemical stripping can deliver a capacity of 125 mAh / g at a discharge rate of 10 C. This indicates that the electrochemical cell not supporting graphene by electrochemical stripping is about 26% better than the 98 mAh / g capacity obtained.

The Coulomb efficiency by various charging / discharging rates of the 1.2 wt% positive electrode material (data point 166) is also shown. At all measured C rates, the Coulomb efficiency remains stable at about 98-100%, and the amount of extracted Li ⁺ and the positive electrode material inserted with lithium iron phosphate encapsulated in graphene by electrochemical stripping is substantial. It was shown that there was almost no loss during charging and discharging.

  The influence of the presence of graphene due to electrochemical exfoliation on the positive electrode carrying lithium iron phosphate encapsulated with graphene encapsulated by electrochemical exfoliation is calculated by calculating the total discharge time at a fixed discharge current and calculating the total discharge time as the actual discharge rate. Can be quantified and used at various charge / discharge rates. As shown in FIG. 17, a battery (curve 170) having a positive electrode material carrying graphene by electrochemical stripping is rapidly replaced with a battery (curve 172) having a positive electrode material not carrying graphene by electrochemical stripping. Compared to the higher retention rate. The results show that the presence of graphene due to electrochemical delamination contributes to an increase in the energy density of the battery material in a high current state, and is thus effective in increasing the power output of the battery. Such an increase is very useful, for example, as the electric vehicle accelerates, increases the maximum allowable current and does not change the voltage of the battery pack of the electric vehicle even uphill.

  The cost of lithium-ion batteries for electric vehicles is very high. Costs can be reduced by extending battery life. FIG. 18 shows an electrochemical cell carrying a lithium iron phosphate positive electrode encased in graphene by electrochemical exfoliation with 0.01 wt% (curve 182) of graphene by electrochemical exfoliation, and 0.8 wt% (curve 184) of electricity. The specific amount of discharge at a fixed discharge current of an electrochemical cell carrying a lithium iron phosphate positive electrode encapsulated with graphene by electrochemical exfoliation with graphene by chemical exfoliation is shown. As a control, an electrochemical cell (curve 180) carrying a positive electrode material having lithium iron phosphate containing no graphene by electrochemical stripping was also similarly tested. The test was performed by activating the test cell for 3 cycles at 0.1 C, and then charging / discharging the test cell continuously at 1.3 C under more stringent test conditions. The life cycle of a positive electrode electrochemical cell with lithium iron phosphate encapsulated in graphene by electrochemical delamination is evident compared to the life cycle of an electrochemical cell carrying a positive electrode material without graphene by electrochemical delamination Increased.

  In order to investigate the cause of excess capacity of the positive electrode material having lithium iron phosphate encapsulated with graphene by electrochemical exfoliation, the positive electrode material to be tested was deposited silica particles inert from graphene by 1.8 wt% electrochemical exfoliation ( (Diameter ˜5-10 μm) was formed, and conductive additives and binders were added depending on the situation. As a control, a positive electrode material was similarly formed on silica particles that did not have graphene by electrochemical peeling. Silica had no obvious effect on the positive electrode capacity. A button-sized battery having a silica cathode material was prepared and tested. By measuring the capacity of silica positive electrode material with graphene by electrochemical exfoliation and silica positive electrode material without graphene by electrochemical exfoliation, it can be provided as a direct measurement for the capacity of graphene flakes by electrochemical exfoliation .

  In FIG. 19, curve 190 and curve 192 show the second cycle voltage curve of the positive electrode material formed from silica particles and silica particles having graphene by 1.8 wt% electrochemical stripping, respectively. Silica particles exhibited a small reversible capacity (curve 190), whereas graphene flakes from electrochemical delamination exhibited a fairly large reversible capacity (curve 192).

In FIG. 20, charge / discharge was performed at a current density of 25 mA / g, and the cycle characteristics of silica particles and the cycle characteristics of silica particles encapsulated with graphene by 1.8 wt% electrochemical stripping were measured. The positive electrode carrying graphene by chemical exfoliation and the positive electrode carrying graphene by 0 wt% electrochemical exfoliation showed rate capability corresponding to 0.5 C and 7.5 C, respectively. Curves 200 and 202 represent the specific amount of discharge of charged silica particles and discharged silica particles, respectively, and curves 204 and 206 respectively discharged with silica particles encapsulated with graphene by 1.8 wt% electrochemical stripping charged. The specific amount of silica particles encapsulated in graphene by 1.8 wt% electrochemical stripping is shown. The rate capability of the graphene encapsulated silica particles by 1.8 wt% electrochemical stripping was still maintained after 6 cycles. The rate capability of silica particles not encapsulated by graphene by electrochemical stripping decreased after several cycles. In the sixth cycle, the charge capacity of the silica particles encapsulated by graphene by 1.8 wt% electrochemical stripping was 53.5 mAh g ⁻¹ , and the discharge capacity was 38.3 mAh g ⁻¹ , which exceeded the capacity of pure silica. . The specific charge capacity of graphene by the electrochemical stripping was about 2970 mAh g ⁻¹ and the discharge capacity was 2120 mAh g ⁻¹ . Since the production of graphene by electrochemical stripping involves an electrochemical reaction in solution, several redox active sites or defects can be activated and maintained on the electrochemical graphene. From these results, it was shown that the graphene flakes by electrochemical exfoliation incorporated into the positive electrode material have improved Li ⁺ ion storage capability and the Li ⁺ ion storage mechanism is reversible.

FIG. 21 shows cyclic voltammetry for silica particles (curve 210) measured at 0.05 V / s and 0.02 V / s (curve 212), 0.05 V / s (curve 214), 0.1 V / s ( The cyclic voltammetry of silica particles encapsulated in graphene by 1.8 wt% electrochemical delamination measured in curve 216) is shown. This demonstrates that an oxidation-reduction reaction has occurred from the oxidation peak 218 at about 3.5-4 V and the reduction peak 219 at about 2.5-3.5 V, which contributes to the storage capacity of Li ⁺ ions. The redox peak is broad, which means that the ability of graphene by electrochemical stripping to improve electrode capacity is not limited to lithium iron phosphate, but also applies to other materials such as other oxides Is possible.

(Other materials)
It is also possible to enhance the performance and capacity of the positive electrode material by adding other materials to the positive electrode material. As shown in FIG. 22A, it is usually possible to make a layered composite cathode particle 220, which includes a cathode material 222, one or more storage materials 224 such as a layered material, high lithium Included are materials 226 that have storage capacity and / or organic materials, one or more functional materials, and / or materials 226. Such composite cathode particles 220 can enhance electrochemical performance such as high speed capability and cycle life improvement, and the voltage curve still shows a curve similar to the cathode material. The capacity of the composite positive electrode particle 220 can be adjusted by superimposing the capacity of the constituent materials on the positive electrode particle. For example, the positive electrode capacity can be increased by the parallel capacity of one or more layers of constituent materials.

  As shown in FIG. 22B, the positive electrode 228 is formed from composite positive electrode particles 220. The positive electrode 228 is used as a positive electrode of an electrochemical cell, and is, for example, a button-type battery 91, a cylindrical battery 93, or a pouch-type battery 95 as shown in FIGS. 9B to 9D, or other types of batteries.

As a specific embodiment in the present invention, materials used for the positive electrode material 222 of the lithium ion battery include lithium iron oxide, lithium iron phosphate, lithium iron phosphorus composite oxide, lithium cobalt composite oxide (LiCoO _2). ), Lithium manganese complex oxide (LiMn ₂ O ₄ ), lithium nickel complex oxide (LiNiO ₂ ), lithium cobalt manganese nickel complex, lithium cobalt manganese nickel complex oxide (NCM), and other positive electrodes One or more lithium-based materials such as materials (e.g., LiFe _(1-x) M _x P _(1-x) O _{2 (2-x)} , 0 ≦ x <1) are included.

The storage material 224 includes a material having a layered structure, a material having a high lithium storage capacity, and / or an organic material. Materials with high lithium storage capacity include materials such as one or more of sulfur, silicon, tin, ceramic materials, lithium sulfide (Li ₂ S), and other materials with high lithium storage capacity. Materials having a layered structure include materials such as transition metal dichalcogenides, one or more MoS ₂ , MoSe ₂ , WS ₂ , WSe ₂ and other transition metal dichalcogenides, and stoichiometric ratios such as MoS _x. And / or any of the corresponding materials. Organic materials include one or more triazines, melamines, and thiophenes.

  The functional material 226 includes one or more electrochemically stripped graphene, nanocarbon tubes, graphene, conductive carbon materials, and other functional materials.

  The present invention will be specifically described with reference to examples. The composite positive electrode material is formed by introducing sulfur into amorphous carbon-coated lithium iron phosphate particles. In order to form a composite cathode material, sulfur powder is put into a heating furnace at 150-200 ° C. to form sulfur vapor. Amorphous carbon-coated lithium iron phosphate particles are placed in the low temperature region of the furnace and sulfur vapor is deposited on the lithium iron phosphate particles so that a gentle gas stream flows from the high temperature region to the low temperature region.

  In FIG. 23, the positive electrode formed from amorphous carbon-coated lithium iron phosphate particles encapsulating sulfur (curve 232) is (200 mAh / g or more) compared with the positive electrode formed from amorphous carbon-coated lithium iron phosphate particles (curve 230). ) Showed improved capacity.

The present invention will be specifically described with reference to embodiments. Both or one of the layered materials MoS ₂ and MoS _x was introduced into amorphous carbon-coated lithium iron phosphate particles to form a composite positive electrode material. In order to form the composite positive electrode material, either or both of alkylammonium thiomolybdenum (MoS ₂ precursor) and ammonium thiomolybdenum (MoS _x precursor) are dissolved in N-methylpyrrolidone, and amorphous carbon-coated phosphorus is dissolved. Lithium iron oxide particles were added into the solution. The solution was heated to 100-200 ° C. and refluxed for 4 hours. The precipitate collected by filtration was dried at high temperature (eg, about 300-1000 ° C.) in a vacuum or nitrogen atmosphere. During the heat treatment, the structure of the MoS ₂ and MoS _x precipitates changed to large crystals.

Reference is again made to FIG. The capacity of the positive electrode formed using amorphous carbon-coated lithium iron phosphate particles encapsulated with MoS _x (curve 234) was similarly improved to 200 mAh / g or more. Furthermore, the positive electrode carrying MoS _x encased in graphene (curve 236) by electrochemical stripping similarly showed a capacity of 200 mAh / g or more.

  The present invention will be specifically described with reference to embodiments. Amorphous carbon coated lithium iron phosphate particles are suitable for small organic molecules such as triazine, melamine, and / or thiophene. For example, triazine evaporates with heat on amorphous carbon-coated lithium iron phosphate particles. Thiophene is a liquid and can be directly mixed with amorphous carbon-coated lithium iron phosphate particles. The molecules can be dissolved in a solvent such as N-methylpyrrolidone or N, N-dimethylformamide and coated onto amorphous carbon-coated lithium iron phosphate particles. The positive electrode formed of such a material also showed an improvement in capacity. The use of such organic molecules as positive electrode additives is not limited to these small molecule forms. For example, the molecule can be a high capacity positive electrode additive to polymerize as a polymer.

  It should be understood that the scope of the present invention is not limited to the above-described embodiments and drawings, but is defined by the claims. However, it should be understood that various changes and modifications can be made without departing from the scope of the invention. For example, in addition to the button type battery, the cylindrical battery, or the square type pouch type battery, the electrode 50 can be used as another battery-like negative electrode and / or positive electrode. Other types of batteries are also used as electrodes for supporting graphene by electrochemical stripping. Embodiments not described in the embodiments of the present invention are within the scope of the following claims.

Claims (28)

Particles containing a plurality of lithium;
A first electrode having at least a portion coated with a carbon layer on the surface of each particle;
Graphene by electrochemical stripping at least partially coated with one or more of the particles,
A second electrode;
A battery comprising an electrolyte solution, wherein at least a portion of the first electrode and at least a portion of the second electrode are in contact with the electrolyte solution.   The battery according to claim 1, wherein the first electrode is a positive electrode. The battery according to claim 1, wherein the first electrode is a negative electrode. The particles include at least lithium iron phosphate, lithium iron oxide, lithium iron phosphorus composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt manganese nickel composite. Or a lithium cobalt manganese nickel-based composite oxide. The battery according to claim 1, wherein the graphene by electrochemical stripping includes a plurality of flakes formed by graphene by electrochemical stripping on carbon. The battery of claim 1, wherein the graphene formed by electrochemical stripping forms an electrode of about 0.001 wt% to about 5 wt%. A plurality of lithium-containing particles;
Each particle surface is at least partially coated with a carbon layer,
The electrode material which has the graphene by the electrochemical peeling which coat | covered the one or more said particle | grains to at least one part. The particles include at least lithium iron phosphate, lithium iron oxide, lithium iron phosphorus composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt manganese nickel composite. The electrode material according to claim 7, wherein one of lithium cobalt manganese nickel-based composite oxide is contained. The electrode material according to claim 7, wherein the carbon layer contains an amorphous carbon layer. The electrode material according to claim 7, wherein the graphene by electrochemical stripping includes a plurality of thin pieces in which graphene by electrochemical stripping is formed on carbon. The electrode material according to claim 7, wherein the graphene formed by electrochemical stripping forms an electrode of about 0.001 wt% to about 5 wt%. 8. The electrode material according to claim 7, wherein the specific volume of the electrode material is at least about 180 mAh / g. The electrode material according to claim 12, wherein a specific amount of the electrode material is about 210 mAh / g. The electrode material according to claim 7, wherein the graphene obtained by the electrochemical stripping includes oxygen of about 20 wt% or less. The electrode material according to claim 7, wherein the magnetic permeability of graphene by the electrochemical peeling is about 90% or less, and the flake resistance is about 10 kΩ / sq or less. The electrode material according to claim 7, wherein the additive material includes at least one of a conductive additive, a binder, a carbon material, and a solvent. The electrode material according to claim 16, wherein the carbon material includes at least one of graphene, soft carbon, hard carbon, nanocarbon tube, or carbon fiber. The electrode material according to claim 7, wherein the electrode material contains at least one of sulfuric acid, silicon, tin, ceramic village material, or lithium sulfide. The electrode material according to claim 7, wherein the electrode material contains a transition metal dichalcogenide. The electrode material according to claim 7, wherein the electrode material contains at least one of triazine and thiophene. The electrode material according to claim 7, wherein the electrode material is a positive electrode material. The electrode material according to claim 7, wherein the electrode material is a negative electrode material. Providing a plurality of particles containing lithium, coating a carbon layer on at least a part of the surface of each particle, forming graphene by electrochemical stripping on the plurality of particles, and graphene by electrochemical stripping Includes at least partially coating one or more of a plurality of particles. The particles are at least lithium iron phosphate, lithium iron oxide, lithium iron phosphorus composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt manganese nickel composite, 24. The method according to claim 23, further comprising one of lithium cobalt manganese nickel based composite oxide. 24. The method of claim 23, wherein the carbon layer comprises an amorphous carbon layer. Forming graphene by electrochemical exfoliation between the plurality of particles mechanically mixes the plurality of particles and graphene by electrochemical exfoliation, and physically combines the plurality of particles containing graphene by electrochemical exfoliation. 24. The method of claim 23, comprising at least one of performing a physical or chemical surface modification or mixing a plurality of particles containing graphene by electrochemical stripping. 24. The method of claim 23, wherein the method comprises graphene formation by electrochemical stripping. In the method of forming graphene by electrochemical stripping, the first electrode having the first carbon material and a part of the second electrode are immersed in an electrolyte solution, and a potential is generated between the first electrode and the second electrode. The method of claim 27, wherein: