KR20150056532A - Graphene-containing electrodes - Google Patents

Abstract

The battery comprises a first electrode containing a plurality of lithium particles, each particle surface comprising an electrochemically peeled graphene coated with at least one or more particles and at least a partially coated carbon layer. The battery includes a second electrode and an electrolytic solution. At least a portion of the first electrode and a portion of the second electrode are in contact with the electrolyte solution.

Description

GRAPHENE-CONTAINING ELECTRODES

Priority claimed by the present invention is disclosed in Taiwan Patent Application No. 101126393 filed on July 20, 2012, and Chinese Patent Application No. 201210254481 filed on July 20, 2012. And U.S. Patent Application No. 13/800, 096, filed March 13, 2013, the entire contents of which are incorporated herein by reference.

Lithium-ion batteries provide excellent electrochemical performance and high capacity, and are used in a variety of energy storage facilities such as solar energy, wind energy, hydropower, and electric trains. It has improved the speed and energy density of lithium-ion batteries to meet the relatively high demand for capacity storage. For example, in order to enhance the electrochemical performance of a positive (+) lithium ion battery with lithium-iron phosphate, carbon is coated on the anode and metal blends (dopants) and / or small particles are formed.

If a battery containing an amorphous carbon-coated lithium-iron-phosphate electrode contains an electrochemically stripped graphene cathode or anode, the high specific capacity, high calorimetric density, and high output will appear without significant voltage polarization action. This type of battery shows low irreversible loss and long cycle life at the first circulating capacity.

In a general situation, the battery contains one first electrode containing a plurality of lithium particles. On all particle surfaces, there is a layer of carbon with a minimum coverage and electrochemically peeled graphene of one or several particles with a minimum coverage. The battery includes one second electrode and one electrolyte. 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 implementation of the battery may include one or more of the following. The first electrode may be one anode (+) or one cathode (-). The battery may be a kind of coin cell battery, a cylindrical battery or a pouch type battery. The particles may be selected from the group consisting of phosphoric acid-iron-lithium, lithium iron oxide, lithium-iron-phosphorous oxide, lithium-cobalt oxide, lithium-manganese oxide, lithium-nickel oxide, lithium-cobalt-manganese- . The electrochemical stripping graphene may comprise an electrochemical stripping graphene which forms a flake on the carbon. The electrochemical stripping graphene amount of the electrode can be formed from about 0.001 wt% to 5 wt%.

In a general aspect, the electrode material comprises a plurality of lithium-containing particles. Each particle surface is coated with at least one layer of carbon and partially coated with at least one or more of the majority of the electrochemical valengines.

The implementation of the electrode material includes one or more of the following examples. The particles may be selected from the group consisting of phosphoric acid-iron-lithium, lithium iron oxide, lithium-iron-phosphorous oxide, lithium-cobalt oxide, lithium-manganese oxide, lithium-nickel oxide, lithium-cobalt-manganese- . The carbon layer may comprise a further layer of amorphous carbon. The electrochemical stripping graphene may comprise an electrochemical stripping graphene which forms a flake on carbon. The electrochemical exfoliating graphene amount of the electrode material can be from about 0.001 wt% to about 5 wt%. The specific capacity of the electrode material is at least about 180 mAh / g, such as about 210 mAh / g. The electrochemical stripping graphene may contain up to about 20 wt% oxygen. The permeability of the electrochemical release graphene may be less than about 90%, and the sheet resistance may be about 10 k OMEGA / sq. The electrode material may include a kind of additive material and includes a conductive additive, an adhesive, a carbonaceous material, or a solvent. In some specific examples, the carbon material may include graphite, soft carbon, hard carbon, carbon nanotubes, and carbon fibers. The electrode material may comprise sulfur, silicon, tin, a ceramic material or lithium sulphide. The electrode material may comprise a transition metal chalcogen compound. The electrode material may comprise triazine or thiophene. The electrode material may be a positive (+) material or a negative (-) material.

In a general situation, the electrode material manufacturing method provides a plurality of lithium-containing particles, wherein each particle surface forms an electrochemically exfoliated graphene on the at least partially coated carbon layer and the plurality of particles.

Implementations of the method may include one or more of the following. The particles may be selected from the group consisting of phosphoric acid-iron-lithium, lithium iron oxide, lithium-iron-phosphorous oxide, lithium-cobalt oxide, lithium-manganese oxide, lithium-nickel oxide, lithium-cobalt-manganese- . The carbon layer may comprise an amorphous carbon layer. The formation of the electrochemical release graphene in the plurality of particles may include mechanical mixing particles and electrochemical release graphene and may be performed by performing physical or chemical surface modification of the multiple particles having electrochemical release graphene, A plurality of particles having pins are mixed. The method may include electrochemical stripping graphene formation. In some specific examples, electrochemical stripping of the graphene results in one electromotive force between the first and second electrodes by immersing the first and second electrodes containing the first carbon material in a solution containing the electrolyte solution

The methods described herein may have one or more advantages. The production of phosphorus-acid-iron-lithium electrodes of coated amorphous carbon containing electrochemical stripping graphene is simple, scalable and compatible with conventional processing methods and materials. Even a small amount of electrochemical exfoliating graphene improves lithium ion battery performance on lithium-ion-phosphate electrodes containing electrochemical release graphene and coated amorphous carbon.

Other features and advantages can be seen in the following description and the scope of the patent application.

1a is an explanatory view of an experimental apparatus for producing electrochemical graphene;
Figure 1b is a flow chart of an electrochemical graphene fabrication process.
Figures 2a, 2b and 2c are optical microscope, scanning electron microscope, and atomic force microscope image of electrochemical graphene flakes, respectively.
Fig. 3 is a statistical measurement image of electrochemical graphene flake thickness.
Figures 4a and 4b show Raman and X spectral emission of electrochemical graphene peel, respectively.
5 is a guide view of an electrode including electrochemical graphene.
6 is a view showing one working process for manufacturing an electrode.
7 is a spray drying process guide view.
Figures 8a and 8b are scanning electron microscope images of phosphate-iron-lithium electrochemical graphene particles.
9A is a specific example of an electrochemical cell.
9B is a specific example of a coin battery.
9C is a specific example of a cylindrical battery.
9D is a specific example of a pouch type cell battery.
Figures 10a and 10b show charging and discharging characteristics of an electrochemical battery of phosphate-iron-lithium electrochemical graphene anode (+).
FIG. 11 is an explanatory view of a phosphate-iron-lithium electrochemical graphene particle. FIG.
FIG. 12a is an image of a transmission electron microscope after filling a phosphate-iron-lithium electrochemical graphene material.
Figures 12b and 12c are transmission electron micrographs after discharge of phosphate-iron-lithium electrochemical graphene material.
FIG. 13 is a transmission electron microscope image of a phosphate-iron-lithium electrochemical graphene material.
Figure 14 shows the relationship between lifetime and capacity of an electrochemical battery with a phosphate-iron-lithium electrochemical graphene anode (+).
FIG. 15 is an explanatory diagram of charging and discharging characteristics of an electrochemical battery containing an amorphous carbon-phosphate-iron-lithium anode (+) with graphene
FIG. 16 is a discharge and coulombic efficiency image of an electrochemical battery with a phosphate-iron-lithium electrochemical graphene anode (+).
FIG. 17 is a graph showing the relationship between the capacity retention rate and discharge rate of a phosphate-iron-lithium electrochemical graphene negative (-) electrochemical battery.
Figure 18 is a life cycle and capacity diagram of a phosphate-iron-lithium electrochemical graphene cathode (-) electrochemical battery.
19 is an anode (+) second cyclic voltage image.
20 is a graph between various positive (+) non-capacity and charge cycles.
21 is a cyclic voltage-current relationship diagram of silica particles having electrochemical graphene.
22a is a diagram of composite anode (+) material.
22b is a positive (+) diagram formed from the composite positive (+) material of FIG. 22a.
Figure 23 is a plot of the capacitance vs. voltage of various composite anode (+) materials.

If a phosphate-iron-lithium electrode battery containing a coating of amorphous carbon contains a cathode (-) or an anode (+) of electrochemical stripping graphene, it exhibits high capacity, high energy density and high output power without significant polarization voltage action. For example, the negative electrode (-) or positive electrode (+) may be formed of lithium-containing particles with electrochemical release graphene. (I. E., At least partial coating). This type of battery shows irreversible loss and long cycle life at a low first circulation capacity.

Electrochemical peeling graphene

Electrochemical stripping graphene flakes can be prepared by electrochemical stripping of graphite in an electrolyte solution (referred to herein as electrochemical graphenes). As described in U.S. Patent Application No. 13 / 170,624 filed on June 28, 2011 and U.S. Patent Application No. 100115655 filed on May 4, 2011, these two patents are all incorporated herein by reference. A large amount of electrochemical graphene flakes are fabricated using electrochemical stripping, and most of the slabs made are composed of only a few layers, and have a low-defect, high-quality crystal structure and low resistance.

Referring to FIGS. 1a and 1b, one working electrode 1 and one ground electrode 2 touch an electrolyte solution 3 (10) to produce electrochemical graphene. For example, the working electrode can be made of graphite, and the ground electrode can be made of a kind of metal such as platinum. A low bias voltage (for example, +2.5 V) from the voltage source 4 is applied to the working electrode 1 (12) to generate ions from the electrolyte 3 and inserted into the graphite structure of the working electrode. Then, a high bias voltage (for example, +10 V) from the voltage source 4 is applied to the working electrode 1 (14) to cause graphite separation in the working electrode 1 to produce a graphene flake, The flakes of graphene can be removed as by using filters and / or centrifuges. In some specific embodiments, the electrochemical graphene can be further processed or improved, such as by using physical or chemical mixing, or using nitrogen or other non-carbon element mixtures. For example, nitric acid or hydrogen peroxide is used to make a p-mixture of electrochemical graphenes or an amine compound to make n-blend of electrochemical graphenes.

In a specific example of the electrochemical stripping process, the working electrode is a graphite rod and the ground electrode is a platinum wire. SO42 aqueous solution (pH value of a solution formed by 2.4 g of 98% sulfuric acid (H2SO4) in 1100 ml of deionized (DI) water and 11 ml of 30% potassium hydroxide solution) is used as the electrolyte solution. Apply an electrostatic bias voltage of +2.5 V to the working electrode and wet the graphite rod for 5 to 10 minutes to allow SO42- ions to slowly flow around the graphite crystal. After applying the +2.5 V bias voltage, the graphite bar is held in one piece. Thereafter, a bias voltage of +10 V is applied. For example, applying a +10 V bias voltage and holding for 30 minutes creates several milligrams of graphene, causing the graphene to peel off. When applying a + 10V bias voltage, graphite is rapidly separated into flakes? And is dispersed on the surface of the electrolyte solution. Filter collection Redisperse in dimethylformamide (DMF) using exfoliated graphene flakes and related products. Centrifuge the graphene solution in dimethylformamide to remove thick graphite particles that are not needed. In some instances, applying a high bias voltage to the working electrode results in switching between +10 V and -10 V to reduce the sulfuric acid oxidation of the separated graphene layer.

2a, 2b and 2c, one optical microscope image, one scanning electron microscope image, and one atomic force microscope (AFM) image each show an example of the graphene flake 20. The width of graphene flakes ranges from a few microns to tens of microns.

Referring to FIG. 3, the thickness range of the graphene flakes of an atomic force microscope survey is about 1.5 to 4.2 nanometers (nm) as shown in FIG. Use the Veeco Dimension-IconR system (Lowell, MA) to create an atomic force microscope image.

Referring to Figure 4a, an example of the Raman spectrum 40 (473 nm laser excitation) of an electrochemical graphene flake shows the presence of the Raman D and D 'bands. Also, referring to FIG. 4B, an example of the binding energy curve C1s 42 of the electrochemical graphene flakes measured by X-ray photoelectron optical branching (XPS) is 286.4 Ev (corresponding to the C-OH button) and 287.8 eV Button) and 288.9 eV (corresponding to the O = C-OH button). However, Raman spectrum 40 and bond energy curve 42 indicate that some defects in the electrochemical graphene flake are due to sulfuric acid oxidation of the graphene. However, the presence of a sharp 2D band at 2700 cm-1 in the Raman spectrum indicates that graphene flakes have a good quality graphite crystal structure, even though defects exist, and that the quality of graphite structure of graphene oxide, Which is better than oxide flakes.

The Raman spectrum is analyzed in a confocal Raman system (NT-MDT, Santa Clara, CA). The wavelength of the laser is 473 nm (2.63 eV), the size of the laser beam spot is about 0.5 μm, and the spectral resolution obtained by a grating of 600 grooves per millimeter is 3 cm -1. One high grating (1800 grooves per millimeter) provides a spectral resolution of 1 cm < " 1 > to obtain a relatively detailed Raman band linearity. The Si peak at 520 cm-1 is used as a reference for wave number correction.

The oxygen content of the electrochemical graphene is lower than the other types of graphene oxygen content. Chemical exfoliating graphene, mechanical exfoliating graphene and graphene oxide reducing graphene. Therefore, electrochemical graphene has relatively higher conductivity than other types of graphene. For example, the oxygen content of the electrochemical graphene flakes described herein may be less than about 20 wt%, such as less than about 18%, less than about 16%, less than about 13%, or about 2% to about 18% , About 16%, about 6% to about 14%, or about 8% to about 12%. The transmittance of electrochemical graphene is about 90% or more, about 91%, 93%, 95%, 97%, or 99% or more. Specific thicknesses may range from about 1.5 nm to about 5 nm (from about 1.5 nm to about 3 nm, from about 2 nm to about 4 nm, from about 2.5 nm to about 4.5 nm, from about 3 nm to about 5 nm) A thin layer resistance of about 10 k? / Sq or less, about 9 k? / Sq or less, about 8 k? / Sq or less, about 7 k? / Sq or less, about 6 k? / Sq or less, about 5 k? / sq, less than or equal to about 3 k [Omega] / sq.

5, an example of the composite electrode 50 includes an electrode material 52 (particles of electrode material), an electrochemical graphene 54 inserted into the electrode material 52, a bonding agent 58, a conductive additive 59, Respectively. The electrode 50 can be used as a negative electrode (-) and / or a positive electrode (+) of a battery such as a lithium ion battery. This would be a coin cell battery, a cylindrical battery or a prismatic battery, and is shown in Figures 9b-9d, respectively.

In the example, the electrode material 52 may be a lithium-based material and may be used as a negative electrode (-) and / or a positive electrode (+) of a lithium ion battery. For example, the precursor in which the electrode material enters the electrode material or the electrode material is a kind of lithium-based material. (E.g., LiFe (1-x) MxP (1-x) O2 (2-x), 0? X <1). (LiMn 2 O 4), lithium-cobalt-manganese-nickel or lithium-cobalt (LiCoO 2), lithium-iron oxide -Manganese-nickel oxide, etc. An amorphous carbon coating layer can be coated with a lithium-based material. Examples of electrode materials include, for example, phosphate-iron-lithium particles of amorphous carbon

In the example, the electrode material 52 may comprise a carbon material, a ceramic material, silicon, tin, other metals or metal oxides. The carbon material may be natural or artificial graphite, soft carbon, hard carbon, carbon-nanotube or carbon fiber (e.g., vapor grown carbon fiber).

The composite electrode 50 may also include an additive material. Examples include conductive additives (59), adhesives (58), carbon materials and solvents. The conductive additive 59 may comprise conductive carbon black (e.g. Super P carbon black, Timcal, Switzerland), primary synthetic graphite (e.g., Timrex KS 6 graphite, Timcal) or conductive additives. The adhesive 58 may comprise vinyl fluoride resin, carboxymethyl cellulose, SB copolymer or other adhesive. The carbon material may include a functional carbon material. Examples are natural or artificial graphite, soft carbon, hard carbon, conductive carbon material, nano carbon tube, carbon fiber (vapor grown carbon fiber) or other carbon material. The solvent may be one or more of N-methyl-2-pyrrolidone, dimethyl phthalate, acetonitrile, alcohol or other solvent.

Typically, the amount of electrochemical graphene 54 in the composite electrode 50 occupies a very small portion of the total material of the electrode 100. For example, the composite electrode 50 may comprise from about 0.001 wt% to about 5 wt% of the electrochemical graphene 54. From about 0.001 wt% to about 2 wt%, from about 0.01 wt% to about 1 wt%, from about 0.05 wt% to about 1.5 wt%, or from about 0.03 wt% to about 1.2 wt%. Although it is described in more detail below, even if the electrode used by the lithium ion battery contains such a small amount of electrochemical graphene, it has a good charge-discharge function.

Referring to FIG. 6, a negative electrode (-) or a positive electrode (+) on which electrochemical graphene is loaded can be combined with an electrochemical graphene and an electrode material or a precursor 60 to produce a composite electrode. For example, electrochemical graphene and electrode material or precursor can be mechanically mixed through ultrasonic waves or uniform mixing. Electrochemical graphene also forms a combination of electrode material or precursor through mechanical mixing, solution mixing and drying, physical or chemical surface modification and / or positive (+) or negative (-) surface physics or chemical mixing.

The mixture of electrochemical graphene and the electrode material can be dried and assembled (62). Thermal drying, spray drying or filter drying. The thermal drying may include holding the powder mixed with the electrochemical graphene and the electrode material by removing the solvent by evaporation of the mixture in a drying furnace or a hot plate. Spray drying may include ejecting the electrochemical graphene and electrode material mixture into a nozzle at a high speed centrifuge. Filter drying may include suction filtration of a mixture of electrochemical graphene and electrode material into agglomerates followed by drying and granulation.

Mixture of electrochemical graphene and electrode material The granules made by drying and granulating can be mixed with additives such as adhesives, conductive additives and / or solvents (ratio of about 8: 1: 1) to form a slurry 64. The solids content of the slurry is from about 40% to about 50%. The slurry is applied to a copper or aluminum foil collector and compressed into an electrochemical test (66) with an electrode for use in a button-type battery facility. Other equipment such as AA, AA or AAA batteries, automotive batteries and other types of batteries also have electrodes containing one or several electrochemical graphenes.

Referring to FIG. 7, in one example, a method of manufacturing an electrode through spray drying is to homogeneously mix an electrochemical graphene and an electrode material or a precursor thereof in a homogenizer 70 to form a homogeneous solution 71. The homogeneous solution 71 is pumped by the peristaltic pump 72 into the spray plate and the spray nozzle 74 rotating at a high speed through the pipeline 76 and is ejected in a high speed centrifugal state. The temperature of the nozzle 74 can be set according to the solution in the homogeneous mixture. In some examples, the temperature of the nozzle 74 is between about 100 ° C and about 200 ° C. The material sprayed using the heater 78 is dried in powder form and the powder is collected in the powder collecting chamber 79. Granulation at high inlet temperature Accelerated processing makes the powder an electrode. Spray drying is applied to mass production of the electrode material.

In one example, amorphous carbon and a small number of layers of electrochemical graphene flakes are coated on the phosphate-iron-lithium (LiFePO4) particles to form an electrode (the body reference is phosphate-iron-lithium electrochemical graphene electrode) . In a 250 ppm electrochemical graphene flake solution in dimethylformamide, the particles are dropped in a 300 nm diameter amorphous carbon layer coating (obtained from Tatung Fine Chemicals Co., Taipei, Taiwan) particles in phosphate-iron-lithium powder. Mix the mixture at 180 ° C and disperse the electrochemical graphene flakes and evaporate the solvent.

Van der Waals force between electrochemical graphene and amorphous carbon-coated phosphate-iron-lithium particles after solvent evaporation wraps the particles with graphene flakes. This lapping protects the phosphate-iron-lithium particles to prevent coagulation and volume expansion.

8a and 8b, the scanning electron microscope image shows that the flake 80 of the electrochemical graphene is actually coated on the surface of the phosphate-iron-lithium particles 82 of the coating amorphous carbon. That is, the corrugation 84 of the electrochemical graphene flake 80 can be observed.

Referring to FIG. 9A, a specific example of the electrochemical battery 90 includes an electrode containing electrochemical graphene. The electrochemical battery 90 can be used to test the electrochemical behavior of the angled electrodes. The electrochemical battery 90 includes one first electrode 92 and is made from a phosphate-iron-lithium electrochemical graphene. The first electrode 92 including the electrochemical graphene may be one negative (-) or positive (+). The electrochemical battery 90 includes a second electrode 94 and is formed from a lithium foil. Electrodes 92 and 94 are immersed in an electrolyte solution 96 containing ions 98 such as Li + ions.

9b-9d, an electrode having electrochemical graphene is used for the negative electrode (-) and / or the positive electrode (+) of the button cell 91, the cylindrical battery 93 and the columnar pouch-

In one example, 10 wt% Super PR graphite and 10 wt% N-methyl-2-pyrrolidone PVDF are added in succession to 80 wt% of the active material. For example, there are phosphate-iron-lithium electrochemical graphenes. The mixture is milled at 400 rpm with stainless steel balls. The slurry is coated on an aluminum foil collector and dried at 110 ° C for 4 hours. Electrochemical batteries such as coin or button batteries are then assembled in an argon-rich glove box. The slurry for drying the electrochemical graphene containing phosphate-lithium-iron is used for the first electrode 92 (negative (-) or positive (+) and lithium foil is used for the second electrode 94 Celgard 2600 separator or Celgard PP / PE / PP Trilayer separator (available from Celgard, Charlotte, NC) can be used as the separator if used for the negative electrode (-)) Electrolyte solution has a 1: 1: 1 dissolved volume ratio In one example, the electrolytic solution contains 1% of ethylene carbonate, ethyl-methyl carbonate and dimethyl carbonate (1: 1: 1 wt%), ) Dissolved in a mixture of 1M lithium hexafluorophosphate.

A positive electrode (+) and a negative electrode (-) that do not contain electrochemical graphene as a control group are prepared and included in an electrochemical battery. For example, the negative (-) composite material is formed of 80 wt% coated amorphous phosphate-iron-lithium, 10 wt% adhesive and 10 wt% conductive additive. These constituents are evenly dissolved in N-methyl-2-phillolidone to obtain about 40 to 50% of the solid slurry. The composite slurry is coated on an aluminum foil collector and compressed with an electrode battery used in a lithium ion button battery. A positive (+) composite material that does not contain electrochemical graphene is prepared using a similar approach.

Phosphate - Iron - Lithium Electrochemistry Graphene Anode (+)

In the following, we define an electrochemical battery that contains a phosphate-iron-lithium electrochemical graphene anode (+) as an electrochemical graphene positive (+) function in the anode (+). An electrochemical battery with a phosphate-iron-lithium electrochemical graphene anode (+) shows good chargeability, high capacity and good cycle life. Examples are non-capacities up to about 210 mAh / g and energy densities up to 600 Wh / kg. This capacity is theoretically higher than the maximum capacity. Without the electrochemical graphene, the simulated anode (+) was predicted to be about 170 mAh / g, and the typical specific capacity of the simulated anode (+) without electrochemical graphene was about 120-160 mAh / g. In addition, the energy density is higher than the typical energy density of about 500 Wh / kg for a similar anode without electrochemical graphene. This high level of capacity and energy density means that the presence of electrochemical graphene enhances the electrochemical performance of the positive (+) composite material.

Referring to FIG. 10a, a battery containing a phosphate-iron-lithium electrochemical graphene anode (+) with electrochemical graphene of 0.8 wt% (curve 102), 1.2 wt% (curve 104) and 2 wt% Shows the curve of the charge voltage of the first charge cycle measured at the 0.1 C load ratio. Test the electrochemical battery (curve 100) against the phosphate-iron-lithium anode (+) without electrochemical graphene. When the amount of electrochemical graphene in the anode (+) increases, the specific capacity of the electrochemical battery also increases. For example, the specific capacity of the positive electrode (+) with electrochemical graphene of 0.8 wt% is 187 mAh / g and the specific capacity of the positive electrode (+) with 2 wt% electrochemical graphene is 210 mAh / g. The theoretical specific capacity of amorphous carbon-coated phosphate-iron-lithium particles is 170 mAh / g. The electrochemical battery is tested at ambient temperature at a voltage range of about 2.0 V to about 3.8 V and at a constant voltage and charged to a constant voltage of 3.8 V until the current reaches 0.05 C.

Referring to FIG. 10b, an electrochemical battery (curve 108) with a phosphate-iron-lithium electrochemical graphene anode contrasted with 0.13 wt% (curve 109) electrochemistry graphene in the same situation is tested. The absence of a clear difference between the two curves indicates that the increase in electrochemical graphene content (as shown in Figure 10A) may have been triggered by a minimum critical amount of electrochemical graphene in the positive (+) material for the improvement of the non-capacity . That is, a positive electrode less than the electrochemical graphene minimum critical amount may not exhibit the improved performance.

Without intending to be bound by theory, the in-situ improvement of an electrochemical battery of an electrochemical graphene flake merging electrode with multiple layers using the availability of additional lithium (Li +) ion storage sites in electrochemical graphenes is described. The main capacity of an electrochemical battery can be attributed to the extraction (charging) of phosphate-iron-lithium particle lithium ions and the injection (discharge) of lithium ions of phosphate-iron-lithium particles. The chemical equation LiFePO4 = FePO4 + Li + + e- can explain this process.

With one or two limiting processes described below, the extraction of lithium ions of the ordered olivine-type structure of the phosphate-iron-lithium particles is restricted. The first limiting process is to spread a limited 'offset'. The diffusion of lithium ions of phosphate-iron-lithium can be limited by the complex ion, external phase, stacking fault, and / or other structural characteristics. The discontinuation of lithium ion diffusion can inhibit the phase shift between phosphate-iron-lithium (LiFePO4) and iron phosphate (FePO4), allowing lithium to be extracted and inserted from the negative (-) or positive (+ The second limiting process is the low electronic conductivity in phosphate-iron-lithium. Low electron mobility prevents the rapid transfer of electrons, so lithium Limit extraction and insertion speed and loss of capacity.

Without being bound by theory, it is believed that improving the capacity of an electrochemical cell containing a negative (-) or positive (+) electrochemical graphene is an advantage of the presence of an additional storage mechanism of lithium ions . &Lt; / RTI &gt; Figure 11 shows the potential storage mechanism of lithium ions. Lithium ions 110 may be inserted into the graphene flake layers in the various layer flakes 112 of the electrochemical graphene on the surface of the phosphate-iron-lithium particles 116 of the coating amorphous carbon 114. The lithium ions 118 can adsorb onto the surface of the carbon 114 of the phosphate-iron-lithium particles. In addition, the reversible redox reaction between lithium (Li) and electrochemical stripping grains is helpful for capacity improvement.

Phosphate-iron-lithium electrochemical graphene materials exhibit this storage mechanism in transmissive electron microscope images after charging (ie after lithium ion extraction) and after discharging (ie after lithium ion insertion). Transmission electron microscope images can be obtained by conducting the test by opening the electrochemical battery immediately after charging or discharging. The positive electrode (+) is washed in ethanol and dried in a glove box. Dried anode (+) material is scraped from aluminum foil, placed in ethanol, and dropped on a copper lattice to produce a transmission electron microscope image.

FIG. 12a shows a high-resolution transmission electron microscope image of 0.8 wt% electrochemically graphene phosphate-iron-lithium electrochemical graphene particle 120 after charging (after Li + extraction at the positive electrode (+)). A non-hard carbon coating layer 122 about 1 nm thick is coated on the lithium-iron-phosphate particles 120. A thin layer of electrochemical graphene 124 of varying thicknesses of about 1.5-2 nm thickness appears on the non-hard carbon coating 122. The layers of graphene flake 124 are typically ordered and laminated in phosphate-iron-lithium particles 120.

Figure 12b shows a high-resolution transmission electron microscope image of particles 125 of phosphate-iron-lithium electrochemical graphene with 0.8 wt% electrochemical graphene after charging (i.e., after inserting Li + into the positive electrode (+)) . FIG. 12c shows an enlarged high-resolution transmission electron microscope image of the phosphate-iron-lithium electrochemical graphene particles 125 after filling. It appears that many of the foils 126 of the electrochemical graphene complex in which the layers are arranged are arranged in a dizzy direction on the surface of the phosphate-lithium-iron particles 125.

The gap between the inner layer and the outer layer of the graphene flake 126 changes before the filling area of the positive (+) particle 125. As an example, the layer-to-layer distance in the graphene flake 126 in the discharged positive (+) particle 125 is 0.372 nm. While the layer-to-layer distance in the graphene flake 124 in the charged positive (+) particle 120 is only 0.34 nm. In another example, the layer-to-layer distance in the discharged positive (+) particle 125 is 0.38 nm and the charged positive (+) particle 120 is 0.31 nm. These layer and interlayer values were determined by the layer and interlayer distances of several locations (at least 12 locations or at least 20 locations) in an average transmission electron microscope image. Rigid graphite, which is structurally perfect and incorporates Li +, has an expected layer-to-layer distance of 0.37 nm.

The structural difference of charged and discharged graphene flakes can be shown when Li + particles are inserted into electrochemical graphene flakes during positive (+) discharges to widen the d-section spacing of electrochemical graphene flakes. In particular, a clear mean (i.e., interlayer) spacing in the electrochemical graphene can provide a framework suitable for insertion of Li + ions into the crystal lattice.

Referring to FIG. 13, a high-resolution transmission electron microscope image is a plan view of the electrochemical graphene flake 130 around the discharged positive (+) particles 132. The presence of the hexagonal structure 134 in the graphene flake 130 represents a hexagonal crystal lattice in the crystal structure of the Li + ion-inserting graphene flake 130. Diagram 136 illustrates making the crystal structure possible within Li + ion implantation grains. The presence of such an inserted Li + ion will help increase the capacity of the positive electrode (+).

The adsorption of Li + ions on the electrochemical graphene surface helps to increase the positive (+) capacity. Typically, surface adsorption of Li &lt; + &gt; ions can lead to instability of the electrochemical battery life cycle. Referring to FIG. 14, the life cycle (curve 140) of an electrochemical battery of phosphate-iron-lithium electrochemical graphene anode (+) with 0.8 wt% electrochemical graphene is stable because the surface adsorption of Li + It does not increase the governance of the electrochemical battery capacity of the kind.

The presence of electrochemical graphene in the phosphate-iron-lithium anode (+) can reduce the irreversible first circulation loss of electrochemical battery capacity. Referring again to Figure 10a, the irreversible loss of electrochemical battery capacity is practically zero at 0.8 wt% (curve 102) and 1.2 wt% (curve 104) electrochemical graphene anode (+). Without the theoretical limitations, this performance can be attributed to a multi-layer highly conductive graphene gating layer equivalent coating on amorphous coated phosphate-iron-lithium particles. An even graphene coating layer is a fast path for electron transfer during charging and discharging. Typically, electron transport within sp2 bonds (bond species present in graphene) is relatively efficient within sp3 bonds (bond types present in amorphous carbon). Effective electron transfer through the electrochemical graphene coating layer improves the kinetics and reversibility of lithium insertion and extraction by allowing electrons to be distributed on all surfaces of the phosphate-iron-lithium particles during charge and discharge cycles.

The irreversible capacity of the 2 wt% electrochemical graphene (curve 106) positive (+) increased by 5%, indicating that irreversible capacity of the amorphous carbon coated phosphate-iron-lithium anode (+ . Typically, the percentage of the first circulation loss increases with increasing carbon content of the phosphate-iron-lithium anode (+). This is because Li + has increased through the diffusion path of the non-hard carbon layer.

2 wt% electrochemical graphene (curve 106) Maintaining the maximum voltage of the anode (+) at 3.4 V means that an even coating of electrochemical graphene does not produce a bad polarizing effect. If the electrochemical graphene of the phosphate-iron-lithium particle is assumed to be uneven (like the lamination of several layers of electrochemical graphene flakes), the behavior of the laminated flakes is not graphite flakes . This will cause additional voltage polarization. Additional voltage polarization can occur at a relatively high percentage by weight of electrochemical graphene. As a control experiment, 2 wt% electrochemically graphene phosphate-iron-lithium particles were prepared in a coarse mixing manner without, in turn, dropping the electrochemical graphene solution. This fabrication is made by graphene lamination, which forms a relatively thick aggregate through this pi-pi laminate interaction. Referring to FIG. 15, the voltage curve (curve 150) in which a positive (+) battery formed in this manner is tested exhibits a definite voltage polarization. This control experiment proves the properties of the water layer of the independent electrochemical graphene flakes, which helps to observe low polarization and low first circulation percentage loss.

Figure 16 shows the discharge rate capability (i.e., non-capacity) of an electrochemical battery of 0.13 wt% (data point 162), 1.2 wt% (data point 164) electrochemical graphene phosphate-iron- . To compare this, we performed an electrochemical battery control test without an electrochemical graphene (data point 160) in the phosphate-iron-lithium anode (+). Various charge / discharge rate specific capacities were tested. In general, when the discharge rate increases, there is no case in which the positive (+) configuration maintains a high discharge current (fast Li + insertion) and the cost is reduced. The positive electrode (+) with electrochemical graphene showed a higher specific capacity than the positive electrode (+) without electrochemical graphene, and at least about 23% capacity at low discharge rate (0.1 C - 1.3 C) At a high discharge rate (2.5 C - 28 C), at least about 26% of the capacity was transferred. For example, a 1.2 wt% electrochemical graphene electrochemical battery can deliver 125 mAh / g of capacity at a 10 C discharge rate, which is about 25% better than the 98 mAh / g capacity of an electrochemical battery without electrochemical graphene.

Here again, a 1.2 wt% anode (data point 166) exhibits a coulombic effect at various charge / discharge rates. The Coulomb effect was stable at about 98-100% for all the tested C ratios, and the amount of Li + added to the phosphate-iron-lithium electrochemical graphene anode (+) insertion and extraction remained fixed, There was little or no loss.

By calculating the total discharge time from the fixed discharge current and converting the total discharge time to the actual discharge rate, the presence of phosphate-iron-lithium electrochemical graphene anode (+) electrochemical graphene in different charge / . Referring to FIG. 17, it was possible to reach a higher retention rate than the electrochemical graphene-free positive battery (curve 172) in the situation where the electrochemical graphene positive (+) battery (curve 170) This result implies that the presence of electrochemical graphene can increase the power output of the battery by helping the battery material to increase the energy density at high currents. This increase will be useful and will not increase the maximum allowable current during the acceleration of the train, nor change the battery voltage of the train when it goes up and down.

The cost of lithium ion batteries in electric trains is expensive. Increasing battery life can lower costs. Figure 18 shows that a phosphate-iron-lithium electrochemical graphene positive (+) electrochemical battery with 0.01 wt% (curve 182) and 0.8 wt% (curve 184) . To compare this, an electrochemical battery (curve 180) was tested in which a phosphate-iron-lithium anode (+) without electrochemical graphene was contrasted. After running three cycle tests of the battery at 0.1 C, we conducted battery charge / discharge tests continuously at 1.3 C in the strict test conditions. Phosphate - Iron - Lithium Electrochemistry Graphene Anode (+) electrochemical battery life was significantly increased over the positive (+) electrochemical battery life cycle without electrochemical graphene.

Phosphate-iron-lithium electrochemical graphene To investigate the source of excess capacity in the positive (+) anode, a 1.8 wt% electrochemical graphene was immersed in inert silica particles (~ 5-10 μm diameter) Respectively. Silica did not have a significant positive effect on the positive (+) capacity. A button size battery of positive (+) material containing silica was prepared and tested. Capacity testing of silica anodic (+) materials with and without electrochemical graphene allowed direct testing of the electrochemical graphene flake capacity.

19, curves 190 and 192 represent the second cyclic voltage curve of the positive electrode (+) formed by silica particles and 1.8 wt% electrochemically graphene silica particles. The silica particles represent one small reversible capacity (curve 190), while electrochemical graphene flakes demonstrate a considerably large reversible capacity (192).

20, cyclic nature testing of silica particles and 1.8 wt% electrochemically graphene silica particles at a fixed charge / discharge current density of 25 mA / g resulted in a positive (+) charge of 1.8 wt% and 0 wt% electrochemical graphene, Which corresponds to a discharge rate of 0.5C and 7.5C, respectively. Curves 200 and 202 represent the specific capacity of the charged and discharged silica particles, respectively. Curves 204 and 206 represent the specific capacities of silica particles with 1.8 wt% electrochemical graphenes charged and discharged, respectively. The discharge capacity of 1.8 wt% electrochemical graphene silica particles was still maintained after 6 cycle cycles. The rate of discharge of the electrochemical graphene-free silica particles weakened after several cycles. The charge (discharge) capacity of 1.8 wt% electrochemically graphene silica particles is 53.5 (38.3) mAh g-1 in the sixth cycle, higher than the pure silica capacity, and the electrochemical graphene charge (discharge) 2970 (2120) mAh g-1. Since the preparation of electrochemical graphenes is involved in the electrochemical reaction in solution, some redox active sites or defects may remain or act on the electrochemical graphene. These results indicate that the electrochemical graphene flake refinement of the positive (+) material enhances the storage capacity of Li + ions and that the storage mechanism of Li + ions is reversible.

21 is a circulating volt ampere image of silica particles (curve 210) tested at 0.05 V / s. And a cyclic voltammetric image of 1.8 wt% electrochemically graphene silica particles tested at 0.02 V / s (curve 212), 0.05 V / s (curve 214) and 0.1 V / s (curve 216). Oxidative peak 218 of about 3.5-4 V and about 2.5-3.5 V reduction peak 219 demonstrate the redox reaction, which is helpful for Li + ion storage capacity. The redox peak broadens to improve the electrochemical graphene capacity of the electrode capacity and add other materials such as other oxides that are not limited to phosphate-iron-lithium.

Other materials

Other materials are added to the anode (+) material to enhance the performance and capacity of the anode (+). 22a, typically a stacked composite anode (+) particle 220 can be made, which includes a positive (+) material 222, one or more types of storage material 224. And / or one or more functional materials (226). &Lt; RTI ID = 0.0 &gt; The capacity of composite anode (+) particles 220 will be adjusted by superposing the constituent material capacity of the positive (+) particles. For example, positive (+) capacity is increased by the parallel dedicated capacity of one or more layers of constituent material.

22b, the anode (+) 228 is formed of a composite anode (+) particle 220. The anode (+) 228 can be used as the anode of an electrochemical battery. A button-shaped battery 91, a cylindrical battery 93, a pouch-shaped battery 95, or other kinds of batteries shown in Figs. 9b-9d, respectively.

Specific examples of the positive (+) material 222 used in a lithium ion battery include the following. One or ten kinds of lithium-based materials (e.g., LiFe (1-x) MxP (1-x) O2 (2-x), 0 x <1), lithium iron oxide, Lithium nickel-cobalt-nickel (NCM) and other positive electrodes such as iron-lithium, lithium-cobalt oxide (LiCoO2), lithium manganese-lithium (LiMn2O4), lithium- (+) Material is an example.

The storage material 224 may comprise a layered material, a high lithium storage capacitor material, and / or an organic material. The high-lithium storage material may include one or more sulfur, silicon, tin, ceramic, lithium sulphide (Li2S) and other high-lithium storage capacity materials. One or more MoS2, MoSe2, WS2, WSe2 and other transition metal chalcogen compounds, and / or a corresponding material having a similar chemical dosage amount ratio such as MoSx. The organic material may comprise at least one triazine, melamine and thiophene.

The functional material 226 may include one or more electrochemical graphene, nanocarbon tube, graphene and conductive carbon material and other functional materials.

In one example, sulfur was added to amorphous coated phosphate-iron-lithium particles to form a composite anode (+) material. To make a composite anode material, the sulfur powder was heated to 150-200 ° C in a furnace and made into sulfur vapor. The amorphous coated phosphate-iron-lithium particles are placed at low temperature in the furnace to allow the sulfur vapor to precipitate on the phosphate-iron-lithium particles, helping the warm gas move from the hot to the cold.

See figure 23, comparison of the anode (+) (curve 230) made of the positive (+) and amorphous carbon coated phosphate-iron-lithium particles made of non-hard carbon coated phosphate-iron-lithium particles with sulfur (curve 232) Indicates an improved capacity.

In one example, the laminate material MoS2 and / or MoSx is placed in amorphous carbon-coated phosphate-iron-lithium particles to form a composite positive (+) material. In order to make the composite anode material, alkyldiammonium-thiomolybdate (a precursor of MoS2) and / or ammonium thiomolybdate (precursor of MoSx) are dissolved in N-methyl-2-pyrrolidone and amorphous carbon- Put the lithium particles into the solution. This solution is heated to 100-200 ° C and refluxed for 4 hours. The precipitate formed by the filter collection is subjected to high temperature drying (about 300-1000 ° C) in a vacuum or nitrogen environment. The structure of the MoS2 and MoSx precipitates changes to relatively large crystals during the heat treatment.

Referring again to FIG. 23, the positive electrode (+) made of amorphous carbon-coated phosphate-iron-lithium particles with MoSx (curve 234) shows an improved capacity of 200 mAh / g. Furthermore, the positive electrode (+) with MoSx of the electrochemical graphene (curve 236) shows a capacity of 200 mAh / g.

In one example, amorphous carbon-coated phosphate-iron-lithium particles may have small organic molecules such as triazine, melamine, and thiophene. For example, triazine is evaporated onto amorphous carbon-coated phosphate-iron-lithium particles. Thiophene can be mixed with phosphoric-iron-lithium particles directly amorphous carbon-coated as a liquid. The anode (+) made of these materials shows improved capacity. The use of these organic molecules as positive (+) additives is not limited to the form of small molecules. For example, a polymer capable of collecting molecules can be used as an additive for a high capacity positive electrode (+).

In order to understand the above description and drawings, and to not limit the scope of the invention, the scope of the patent application is not limited to such contents. I have already described several concrete examples, but many modifications are necessary for understanding. For example, in addition to a coin cell battery, a cylindrical battery or a columnar pouch battery, the electrode 50 may be used as a negative (-) and / or positive (+) battery of another battery. Other types of batteries can also be used as electrodes for electrochemical graphenes. Other specific examples are within the scope of the following patent applications.

Claims (28)

A first electrode, a second electrode, and an electrolytic solution,
A plurality of lithium-containing particles;
A carbon layer at least partially coating each surface of at least a portion of the particles;
Electrochemically peeled graphene that at least partially coats one or more of the plurality of particles,
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 method of claim 1, wherein the particles are selected from the group consisting of phosphate-iron-lithium, iron oxide-lithium, phosphorus-iron-lithium, nickel oxide-lithium, lithium-cobalt-manganese- A battery containing one. The battery according to claim 1, wherein the electrochemical stripping graphene comprises a plurality of flakes of electrochemical stripping grains formed on carbon. The battery of claim 1, wherein the electrochemical release graphene forms about 0.001 wt% to about 5 wt% of the electrode. A plurality of lithium-containing particles;
A carbon layer at least partially coating each surface of at least a portion of the particles;
An electrode material comprising electrochemically peeled graphene that at least partially coats one or more plurality of particles. The method of claim 7 wherein the particles are selected from the group consisting of phosphate-iron-lithium, iron oxide-lithium, phosphorus-iron-lithium, cobalt oxide-lithium, manganese oxide- And lithium oxide-cobalt-manganese-nickel oxide. 8. The electrode material according to claim 7, wherein the carbon layer comprises one layer of amorphous carbon. 8. The electrode material according to claim 7, wherein the electrochemical stripping graphene comprises a plurality of flakes forming electrochemical stripping grains on carbon. 8. The electrode material of claim 7, wherein the electrochemical stripping grains form about 0.001 wt% to about 5 wt% of the electrode. The electrode material according to claim 7, wherein the specific capacity of the electrode material is at least about 180 mAh / g. 8. The electrode material according to claim 7, wherein the specific capacity of the electrode material is about 210 mAh / g. 8. The electrode material of claim 7, wherein the electrochemical release graphene comprises up to about 20 wt% oxygen. 8. The electrode material according to claim 7, wherein the electrochemical release graphene has a transmittance of about 90% or less and a sheet electrical resistance of about 10 k? / Sq or less. 8. The electrode material according to claim 7, comprising an additive comprising at least one of a conductive additive, an adhesive, a carbonaceous material, or a molten metal. 17. The electrode material according to claim 16, wherein the carbon material comprises at least one of graphite, soft carbon, hard carbon, nano carbon tube or carbon fiber. The electrode material according to claim 7, comprising at least one of sulfur, silicon, tin, ceramic material or lithium sulfide. 8. The electrode material according to claim 7, comprising a transition metal chalcogenide compound. 8. The electrode material according to claim 7, comprising at least one of triazine or thiophene. The electrode material according to claim 7, wherein the electrode material is a positive electrode material. 8. The electrode material according to claim 7, wherein the electrode material is a negative electrode material. Providing a carbon layer that at least partially coats a plurality of lithium-containing particles and a respective surface of at least a portion of the particles; And
Forming electrochemical stripping grains on the plurality of particles,
Wherein the electrochemical stripping grains at least partially coat at least a plurality of particles. 24. The method of claim 23 wherein the particles are selected from the group consisting of phosphate-iron-lithium, iron oxide-lithium, phosphorus-iron-lithium, cobalt oxide-lithium, manganese oxide- And lithium-cobalt-manganese-nickel. 24. The method of claim 23, wherein the carbon layer comprises an amorphous carbon layer. 24. The method of claim 23, wherein the step of making electrochemical stripping grains in a plurality of particles comprises:
Mechanically mixing the plurality of particles and the electrochemical peeling graphene; performing physical or chemical surface modification of the plurality of particles with the electrochemical peeling graphene; And doping the particles. 24. The method of claim 23, comprising forming the electrochemical stripping graphene. 28. The method of claim 27, wherein forming the electrochemical stripping graphene comprises:
Immersing a part of the first electrode containing the first carbon material and a part of the second electrode in a solution containing an electrolytic solution; And
And inducing an electromotive force between the first electrode and the second electrode.

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