TW201438990A - Graphene sheet composition - Google Patents

Abstract

One embodiment of the present invention contains graphene as the main component within a range from 30% to less than 100% in a graphene sheet composition and is obtained by treating graphite in a supercritical fluid.

Description

Graphene sheet composition

The present invention relates to a graphene sheet composition, a negative electrode active material for a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, a battery pack, a resin composite material, and a method for producing a graphene sheet composition, and A device for manufacturing a graphene sheet composition.

Graphene is attracting attention in terms of carbon materials. The complete graphene system consists only of a collection of hexagonal unit cells with an electronic mobility of up to 15,000 cm ² V ^-1 S ^-1 at room temperature and excellent thermal/chemical stability. Because of the large specific surface area and the like, it is expected that many uses such as next-generation electronic materials or power storage applications can be expected.

However, if a pentagonal or heptagonal unit cell exists in the collection of hexagonal unit cells, it becomes a lattice defect, and the characteristics expected for graphene cannot be sufficiently guided. Based on this point of view, a complete graphene composed of only a collection of hexagonal unit cells is required.

Non-Patent Document 1 discloses a method of treating graphite in a supercritical fluid of ethanol or DME (dimethyl ether) for 1 hour as a graphene sheet having about 10 layers laminated from a monoatomic layer. It Production method.

On the other hand, a lithium ion secondary battery for use in power storage is mounted on a portable device such as a mobile phone or a notebook personal computer because of its high capacity and small size and weight. Then, these portable devices are required to further improve the performance of lithium ion secondary batteries with high performance, high functionality, and increased use. Here, the carbon material used as the negative electrode active material of the lithium ion secondary battery is generally roughly classified into a graphite-based carbon material and an amorphous-based carbon material. Graphite-based carbon materials have an advantage of having a high energy density per unit volume compared to amorphous carbon materials. Therefore, in a lithium ion secondary battery for a portable device that is required to be miniaturized and has a large charge and discharge capacity, a graphite-based carbon material is generally used as the negative electrode active material.

Although the theoretical value of the discharge capacity of graphite is 372 mAh/g, since an SEI (solid electrolyte interface) film is formed in the initial insertion of lithium ions in an actual lithium ion secondary battery, the discharge capacity can only be obtained at 300 mAh/g. about.

Patent Document 1 discloses a lithium ion secondary battery using a graphene compound having 18 or more and 144 or less carbon atoms having hexabenzocoronene as a basic skeleton as a negative electrode active material.

Recently, as a material for replacing graphite, a metal capable of adsorbing/releasing lithium ions such as ruthenium, tin, aluminum, or tungsten having a high discharge capacity or an alloy-based material thereof is used as the negative electrode active material. For example, the theoretical value of the lanthanide discharge capacity is 4199 mAh/g, and the theoretical value of the tin-based discharge capacity is 994 mAh/g.

However, these metal/alloy materials have a large volume change rate when lithium ions are inserted, for example, 矽 is 4.0 times, tin is also 3.6 times, and the volume change rate of graphite is 1.1 times, which is very large. Moreover, such a metal/alloy material has a large volume change accompanying the adsorption/release of lithium ions, and is repeatedly adsorbed/released between the metal/alloy material and the conductive auxiliary agent. The interface between the metal/alloy material and the current collector may be peeled off, or the metal/alloy material itself may be damaged. Therefore, the discharge capacity is drastically lowered, and there is a problem that the cycle characteristics of the lithium ion secondary battery are extremely poor.

Therefore, it has been proposed to mix a carbon material such as graphite with such a metal/alloy material, or to coat a metal or carbon which does not adsorb/release lithium ions.

However, there is a problem that the irreversible capacity is large and the cycle stability is lacking, and the practical battery cycle performance cannot be satisfied.

Patent Document 2 discloses a negative electrode composite compound for a lithium ion battery mainly comprising a nanographene platelet. In this case, the negative electrode composite compound for a lithium ion battery includes a) a plurality of graphene sheets having particles having a size of micrometers or nanometers capable of adsorbing and desorbing lithium ions, and b) having a nanometer size. Further, the graphene sheet is a single-layer graphene sheet or a layer in which graphene sheets are superposed, and has a thickness of 100 nm or less. Further, at least the particles or the coating are at least physically or chemically bonded to one of the graphene sheets. In addition, the amount of graphene sheets is 2 to 90% by mass, and the amount of particles or coatings is 98 to 10 the amount%.

Patent Document 3 discloses a resin composition containing a synthetic resin and exfoliated graphite. In this case, the laminate of the exfoliated graphite-based graphene sheets has a laminate number of 150 or less and an aspect ratio of 20 or more.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-151956

[Patent Document 2] Japanese Patent Publication No. 2011-503804

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2012-77286

[Non-patent literature]

[Non-Patent Document 1] Annual Report of the Industrial Technology Research Institute of Heisei 21, p. 692

However, the method for producing graphene sheets of Non-Patent Document 1 is a batch type (fractional type), and there is a problem that it is difficult to produce graphene in a short time.

Further, the graphene sheet of Non-Patent Document 1 has a problem that the content of graphene is small.

Further, there is a problem that the discharge capacity and the rapid charge and discharge characteristics of the lithium ion secondary batteries of Patent Documents 1 and 2 are insufficient.

Further, the resin composition of Patent Document 3 has a problem that conductivity is insufficient.

In the same manner as the present invention, it is an object of the invention to provide a graphene sheet composition containing graphene as a main component.

In the same manner as the present invention, it is an object of the invention to provide a negative electrode active material for a lithium ion secondary battery which can improve the discharge capacity and rapid charge and discharge characteristics of a lithium ion secondary battery.

The object of the present invention is to provide a conductive auxiliary agent capable of improving the discharge capacity and rapid charge and discharge characteristics of a lithium ion secondary battery.

The object of the present invention is to provide a resin composite material having excellent conductivity.

In the same manner as the present invention, it is an object of the invention to provide a method for producing a graphene sheet composition which is capable of producing a graphene sheet composition containing graphene as a main component in a short period of time.

The object of the present invention is to provide a method and apparatus for producing a graphene sheet composition capable of producing a graphene sheet composition in a short period of time.

The same state of the present invention is in the graphene sheet composition, and graphene is contained as a main component in a range of 30% or more and less than 100%. And obtained by treating graphite in a supercritical fluid.

In the same manner as the present invention, the negative electrode active material for a lithium ion secondary battery contains the above graphene sheet composition.

In the same manner as the present invention, the negative electrode active material for a lithium ion secondary battery contains the above-described graphene sheet composition and metal particles capable of adsorbing and desorbing lithium ions.

In the same manner as in the present invention, the conductive auxiliary agent contains the above graphene sheet composition.

In the same manner as in the present invention, the resin composite material contains a synthetic resin and the above graphene sheet.

A state in which the present invention is a method for producing a graphene sheet composition, comprising: (a) a step of supplying a solvent containing graphite to a supercritical processing field; and (b) supplying the supercritical processing field to the supercritical processing field. a step of bringing the solvent into a supercritical state; and (c) returning the solvent in the supercritical state to a non-supercritical state, and performing the flow of the solvent in a continuous flow manner in the steps (a) to (c), The steps (a) to (c) are repeated a plurality of times continuously and/or discontinuously.

In the same manner as in the present invention, in the apparatus for producing a graphene sheet composition, there are: (a) means for supplying a solvent containing graphite to a supercritical treatment field; and (b) supplying to the supercritical treatment field. a means for the solvent to be in a supercritical state; and (c) means for returning the solvent in the supercritical state to a non-supercritical state, and the means (a) to (c) are performed by continuously flowing the solvent.

That is, the present invention provides the following invention.

(1) A graphene sheet composition obtained by treating graphite in a supercritical fluid by containing graphene as a main component in a range of 30% or more and less than 100%.

(2) The graphene sheet composition according to the above item (1), which contains at least 7 layers of graphene sheets of 15% or less.

(3) A negative electrode active material for a lithium ion secondary battery, which comprises the graphene sheet composition according to the above (1).

(4) A negative electrode for a lithium ion secondary battery, which comprises the negative electrode active material for a lithium ion secondary battery according to the above (3).

(5) A lithium ion secondary battery characterized by having the negative electrode for a lithium ion secondary battery according to the above (4).

(6) A battery pack characterized by having the lithium ion secondary battery according to the above item (5).

(7) A negative electrode active material for a lithium ion secondary battery, comprising the graphene sheet composition according to the above (1), and metal particles capable of adsorbing and desorbing lithium ions.

(8) The negative electrode active material for a lithium ion secondary battery according to the above (7), wherein the metal particles contain one or more selected from the group consisting of aluminum, lanthanum and tin.

(9) A negative electrode for a lithium ion secondary battery, which comprises the negative electrode active material for a lithium ion secondary battery according to the above (7).

(10) A lithium ion secondary battery characterized by having the negative electrode for a lithium ion secondary battery according to the above (9).

(11) A battery pack characterized by having lithium ions as in the above item (10) Secondary battery.

(12) A conductive auxiliary characterized by comprising the graphene sheet composition according to the above item (1).

(13) An electrode comprising the conductive auxiliary agent according to the above item (12).

(14) A battery characterized by having the electrode of the above item (13).

(15) A resin composite material comprising the graphene sheet composition according to the above (1), and a synthetic resin.

(16) A method for producing a graphene sheet composition, comprising: (a) a step of supplying a solvent containing graphite to a supercritical treatment field; and (b) a solvent supplied to the supercritical treatment field a step of supercritical state; and (c) a step of returning the solvent in a supercritical state to a non-supercritical state, wherein in the steps (a) to (c), the solvent flows in a continuous flow manner, and The above steps (a) to (c) are repeated plural times continuously and/or discontinuously.

(17) The method for producing a graphene sheet composition according to the above item (16), wherein the steps (b) and/or (c) are carried out in a state where vibration is applied.

(18) The method for producing a graphene sheet composition according to the above item (16), wherein the number of times of repeating the steps (a) to (c) continuously and/or discontinuously is 10 or more and 100 or less.

(19) A device for manufacturing a graphene sheet composition characterized by There are: (a) means for supplying a solvent containing graphite to a supercritical treatment field; (b) means for causing a solvent supplied to the supercritical treatment field to become a supercritical state; and (c) making the supercritical state The solvent returns to a non-supercritical state, and the above-mentioned means (a) to (c) perform the flow of the solvent in a continuous flow manner.

(20) The apparatus for producing a graphene sheet composition according to the above item (19), wherein the means (b) and/or (c) are means for applying vibration.

According to the state of the present invention, a graphene sheet composition containing graphene as a main component is provided.

According to the same aspect of the present invention, it is possible to provide a negative electrode active material for a lithium ion secondary battery which can improve the discharge capacity and rapid charge and discharge characteristics of a lithium ion secondary battery.

According to the state of the present invention, it is possible to provide a conductive auxiliary agent capable of improving the discharge capacity and rapid charge and discharge characteristics of a lithium ion secondary battery.

According to the state of the present invention, a resin composite material excellent in electrical conductivity can be provided.

According to the same aspect of the present invention, a method for producing a graphene sheet composition capable of producing graphene-containing materials in a short time can be provided. A graphene composition composed of a main component.

According to the same aspect of the invention, it is possible to provide a device for producing a graphene sheet composition which is capable of producing a graphene sheet composition in a short time.

100‧‧‧Manufacturing device for graphene sheet composition

110‧‧‧Materials Department

115‧‧‧ storage container

120‧‧‧Solvent-dispersed graphite

125‧‧‧Pipe

130‧‧‧ pump

150‧‧‧Supercritical Processing Department

155‧‧‧Supercritical processor

160‧‧‧Vibration means

165‧‧‧Pipe

168‧‧‧Cooling trough

170‧‧‧Switching valve

172‧‧‧Pipe

174‧‧‧Pipe

180‧‧‧Recycling Department

185‧‧‧ container

[Fig. 1] is a view schematically showing an example of a method for producing a graphene sheet composition.

[Fig. 2] is a view schematically showing an example of a manufacturing apparatus of a graphene sheet composition.

[Fig. 3] is a perspective view showing an example of a lithium ion secondary battery.

[Fig. 4] An example of a TEM photograph of the graphene sheet composition of Example 3.

[Fig. 5] A graph showing the results of evaluation of the number of laminations of the graphene sheet compositions of Examples 1 to 4.

Next, the form for carrying out the invention will be described with reference to the drawings.

(graphene sheet composition, method for producing the same, and manufacturing apparatus)

A method for producing a graphene sheet composition, comprising: (a) a step of supplying a solvent containing graphite to a supercritical processing field; and (b) supplying the same to the supercritical processing field; The step of supercritical treatment of the solvent in the supercritical state; and (c) the step of returning the solvent in the supercritical state to a non-supercritical state. At this time, in the steps (a) to (c), the solvent is continuously flowed, and the steps (a) to (c) are repeated continuously and/or discontinuously. Thereby, the graphene sheet composition having a large content of graphene can be produced in a short time compared to the production method by the conventional batch method.

Further, in the present specification and the patent application, a laminate in which N layers of graphene is laminated is referred to as an N-layer graphene sheet. However, N is an integer from 2 to 20.

Further, in the present specification and the patent application, a composition containing graphene and/or N-layer graphene sheets is referred to as a graphene sheet composition.

Further, the non-supercritical state refers to, for example, a state in which a liquid or a gas is formed at a normal temperature or a normal pressure at a pressure higher than a normal pressure at a normal temperature.

At this time, the steps (b) and/or (c) are preferably carried out in a state where vibration is applied.

In the method for producing a graphene sheet composition, the graphite of the raw material may be partially or completely peeled off in the supercritical fluid by the step (b) to form a graphene sheet composition.

Further, in the method for producing a graphene sheet composition, the steps (a) to (c) are repeated a plurality of times continuously and/or discontinuously.

Further, repeating the steps (a) to (c) continuously means that after the steps (a) to (c) are performed, the next step (a) to (c) is performed. Step. On the other hand, repeating the steps (a) to (c) discontinuously means that the solvent containing the graphene sheet composition discharged from the supercritical treatment site after the steps (a) to (c) is performed ( After the dispersion liquid is temporarily introduced into the storage container, it is taken out from the storage container, and the next steps (a) to (c) are performed. That is, repeating the steps (a) to (c) discontinuously means repeating the steps of introducing the dispersion into the storage container after performing the steps (a) to (c), and removing the dispersion from the storage container. Take out and proceed to the next step (a) to (c). In addition, the raw material tank in which the graphite-containing solvent is stored before the steps (a) to (c) may be used in combination with the storage container introduced after the steps (a) to (c), and repeated. One (a) to (c) steps.

As described above, in the method for producing a graphene sheet composition, the non-super is performed under the low temperature/low pressure from the step (b) (the supercritical state at high temperature and high pressure) to the step (c) in a short time. Pressurization/opening in a critical state can effectively produce a graphene sheet composition as compared with a conventional production method in a closed container (batch type). For example, in Example 3 in which 12 repeated treatments were carried out in about 16 minutes, since the supercritical treatment field of, for example, 420 ° C and 12 MPa was rapidly opened to normal temperature/normal pressure, it was short-time compared with the batch type. Repeated heating/cooling is performed abruptly. As a result, the peeling effect of graphite is improved. Here, in the batch type, it takes 120 hours to carry out 12 times of about 1 hour/batch processing.

Hereinafter, each step will be described in detail using FIG. 1 .

(Step S110)

First, a solvent containing graphite is prepared.

Although graphite is not specifically limited, natural graphite, artificial graphite, etc. are mentioned.

Natural graphite is classified into flaky graphite, scaly graphite, earthy graphite, etc. depending on its properties.

Artificial graphite can be fired into petroleum heavy oil, carbon heavy oil, petroleum coal char, coal coke, and pitch carbon fiber at 1500~3200 °C in a non-oxidizing environment. Manufacturing. In this case, baking may be performed in the presence of a graphitization catalyst such as a boron compound.

The properties of the purity and crystallinity of graphite are not particularly limited.

Further, in the present specification and the patent application, the particle diameter of the particles means the primary particle diameter.

In addition, the primary particle diameter d of the particles can be determined by the BET method after the specific surface area, by the formula S=6/ρd

Calculated by conversion. Here, the specific surface area of the S-based particles and the density of the ρ-based particles.

In the present specification and the scope of the patent application, the solvent means a liquid or a gas at a normal temperature and a normal pressure which can be a supercritical fluid.

The solvent is not particularly limited, and examples thereof include water, alcohols, ethers, esters, ketones, hydrocarbons, dimethyl hydrazine, and N,N'-dimethyl methacrylate. Liquids such as guanamine, N,N'-dimethylacetamide, 1-methyl-2-pyrrolidone, carbon dioxide, nitrogen, oxygen, helium, argon, ammonia, nitrogen monoxide, lower alkanes, alkenes, etc. Gas. Among them, preferred are water, methanol, ethanol, dimethyl ether, N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), and carbon dioxide.

The particle diameter (average particle diameter) of the graphite as a raw material is usually 0.1 to 100 μm, preferably 1 to 50 μm.

The concentration of graphite in the solvent containing graphite is usually 0.1 to 100 mg/mL, preferably 1 to 10 mg/mL.

Next, the prepared graphite-containing solvent is supplied to a supercritical treatment field (for example, a reaction tube) for supercritical treatment of graphite. At this time, the solvent containing graphite may be temporarily stored in the raw material tank, and the solvent containing graphite may be supplied from the raw material tank to the supercritical processing field using, for example, a pump.

The rate at which the solvent containing graphite is supplied to the supercritical treatment field is usually from 1 to 1000 mL/min, preferably from 5 to 100 mL/min.

(Step S120)

Next, in the supercritical treatment field, the graphite is subjected to supercritical treatment in an environment in which the solvent becomes a supercritical state.

For example, in the case where the solvent is ethanol, the critical temperature is 241 ° C and the critical pressure is 6.1 MPa. Therefore, the supercritical treatment system has a temperature of 241 ° C or higher and a pressure of 6.1 MPa or more, for example, a temperature of 420 ° C and a pressure of 12 MPa.

In the case where the solvent is methanol, the supercritical treatment field system temperature is 240 ° C or higher and the pressure is 8.1 MPa or more.

In the case where the solvent is water, the supercritical treatment field temperature is 374 ° C or higher and the pressure is 22.1 MPa or more.

As described above, the temperature and pressure of the supercritical treatment field are set by the critical temperature and critical pressure of the solvent used.

The time during which the solvent is maintained in the supercritical state, that is, the time during which the graphite remains in the supercritical fluid, is typically from 0.5 seconds to 10 minutes.

By treating the graphite in a supercritical fluid, at least a portion of the graphite, the interlayer bonding thereof is cut off and separated into layers. Thereby, it is peeled off into the graphene sheet composition containing graphene.

At this time, vibration can be applied to the supercritical processing field as needed. Thereby, more graphene can be produced.

The method of applying vibration to the supercritical processing field is not particularly limited, and examples thereof include a method of applying mechanical vibration to a supercritical processing field, a method of applying vibration to a supercritical processing field by ultrasonic waves, and the like.

In the method of applying vibration to a supercritical processing field by ultrasonic waves, vibration can be easily applied to the supercritical processing field by the cavitation effect of the ultrasonic wave, the effect of the vibration acceleration, the effect of the straight flow, and the like. .

(Step S130)

Second, the solvent that becomes the supercritical state returns to the non-supercritical state. Thereafter, the solvent containing the graphene sheet composition is discharged from the supercritical processing field.

Non-supercritical state, usually from room temperature to the boiling point of the solvent, and at atmospheric pressure.

In the non-supercritical state, vibration can also be applied as needed. Thereby, more graphene can be produced.

In the non-supercritical state, the method of applying vibration is not particularly limited, but the same method as the method of applying vibration to the supercritical processing field can be used.

Next, the solvent (dispersion liquid) containing the graphene sheet composition discharged from the supercritical treatment site is continuously supplied to the supercritical treatment field continuously, and the second supercritical treatment is performed. Thereafter, after the solvent which has become the supercritical state returns to the non-supercritical state again, the solvent containing the graphene sheet composition is discharged from the supercritical treatment field.

(Step S140)

Hereinafter, steps (a) to (c) are repeated.

The number of times of steps (a) to (c) is repeated, and is usually 2 or more, preferably 10 or more, and more preferably 30 or more.

At this time, in order to manufacture a desired graphene sheet composition, the number of times of repeating steps (a) to (c) is arbitrarily set. If the number of times of repeating steps (a) to (c) is extremely large, the time required for the manufacture of the graphene sheet composition becomes long, and the manufacturing cost is increased. Therefore, the number of times of steps (a) to (c) is repeated, preferably 100 times or less.

The graphene sheet composition can be produced by the above steps.

If the flow rate is, for example, 10 ml/min for ethanol, 10 mg/min for graphite, 420 °C for supercritical treatment, 12 MPa for supercritical treatment, and short for supercritical fluid in supercritical treatment. The conditions for treating the graphite were repeated 12 times (a) to (c), and the graphene content in the graphene sheet composition was 35%. Further, when the steps (a) to (c) are repeated 48 times, the content of graphene is 90% or more.

Further, the content of each component in the graphene sheet composition is based on the type of the supercritical fluid, (a) the flow rate of the solvent containing the graphite to the heat treatment field, the input amount of the graphite, the temperature of the supercritical treatment field, The pressure of the supercritical treatment field, the time during which the graphite stays in the supercritical treatment field, the presence or absence of the storage container, the storage amount of the storage container, and the like may be arbitrarily designed.

As described above, in the method for producing a graphene sheet composition, a graphene sheet composition containing graphene as a main component can be produced.

In addition, in the specification and the patent application, the content [%] of graphene or N-layer graphene sheets in the graphene sheet composition means that the number of graphene or N-layer graphene sheets is relative to The ratio of the total number of graphene and graphene sheets [%] measured by the man-scattering spectrometry and based on the position of the 2D-Band (for the position measurement of 2D-Band, etc., refer to Chem. Eur. J. 2010, 16 , p6488-6494).

If the position of 2D-Band is less than 2685cm ^-1 , it corresponds to graphene, if it is 2685cm ^-1 or more and less than 2695cm ^-1 , it corresponds to 2~3 layers of graphene sheets, if it is 2695cm ^-1 or more 2705 cm ^-1 corresponds to 4 to 6 layers of graphene sheets, and if 2705 cm ^-1 or more, it corresponds to 7 or more layers of graphene sheets.

For example, a graphene sheet composition is placed on a sample substrate, and a position of 2D-Band at 30 points is measured by Raman scattering spectrometry, and a graphene sheet is used when the position of 2D-Band at 9 or more points is less than 2685 cm ^-1 . The content of graphene in the composition is 30% or more.

Further, when the position of 2D-Band at 9 o'clock is 2685 cm ^-1 or more and less than 2695 cm ^-1 , the content of the 2 to 3 layers of graphene sheets in the graphene sheet composition is 30%.

Further, when the position of 2D-Band below 3 points exceeds 2705 cm ^-1 , the content of 7 or more graphene sheets in the graphene sheet composition is 10% or less.

In addition, the measurement points of the Raman scattering spectrometry can be increased to 60 points, 100 points, and the like.

The graphene sheet composition contains graphene as a main component in a range of 30% or more and less than 100%, and other components other than graphene further contain 2 to 3 layers of graphene sheets and 4 to 6 layers. One or more components selected from the group consisting of graphene sheets and 7 or more graphene sheets.

Further, in the present specification and the patent application, the inclusion of graphene as a main component means that the content of graphene is more than the content of each layer of graphene sheets of 2 to 20 layers.

Here, the content of graphene and each layer of graphite of 2 to 20 layers The content of the ene sheet was determined by measuring the thickness [nm] of any 30 parts of the graphene sheet composition by using an SPM (Scanning Probe Microscope) method.

Further, the measurement portion of the thickness of the graphene sheet composition may be increased to 60 parts, 100 parts, or the like.

The median diameter (D50) of the graphene and graphene sheets depends on the type of graphite (crystallinity, crystallite size, particle diameter, etc.) of the raw material, but is usually several μm to several nm, preferably 1 μm to 5 nm. More preferably, it is 200 nm to 10 nm.

Further, the median diameter (D50) of the graphene and graphene sheets can be measured using a well-known laser diffraction method.

The graphene sheet composition is a graphite stripper having a laminate of more than 20 layers of graphite or graphene separated by a separation method by centrifugation or a floating density separation method in a specific dispersion medium. Purification is carried out.

Fig. 2 is a view schematically showing an example of a manufacturing apparatus of a graphene sheet composition.

The manufacturing apparatus 100 of the graphene sheet composition is provided with the raw material part 110, the supercritical processing part 150, and the collection part 180.

The raw material portion 110 stores a portion containing a solvent of graphite which is a raw material of the graphene sheet composition. The raw material portion 110 includes a storage container 115 in which a solvent 120 (dispersion liquid) is accommodated, and the solvent 120 (dispersion liquid) is dispersed with graphite.

The supercritical processing unit 150 is made by making the solvent supercritical The portion where the graphite is subjected to supercritical treatment. The supercritical processing unit 150 is a supercritical processor 155 having heat resistance and pressure resistance. Further, the supercritical processing unit 150 has a vibration means 160. The vibration means 160 is configured to apply vibration to the supercritical processor 155. However, the vibration means 160 may be omitted.

A pipe 125 is provided between the raw material unit 110 and the supercritical processing unit 150, and the pipe 125 connects the storage container 115 to the supercritical processor 155. A pump 130 is provided in the piping 125.

The recovery unit 180 is a portion that recovers the solvent containing the graphene sheet composition after the supercritical treatment unit 150 is supercritically treated. The collection unit 180 is provided with a container 185. A liquid for cooling is accommodated in the container 185.

A pipe 165 is connected to the outlet side of the supercritical processing unit 150, and the pipe 165 is configured to pass through the inside of the cooling tank 168. The cooling bath 168 cools the temperature of the solvent containing the graphene sheet composition after the supercritical treatment to, for example, room temperature. At this time, a pressure reducing valve is provided in front of or behind the cooling groove 168.

A pipe 172 is connected to the recovery unit 180. A switching valve 170 is connected between the pipe 165 passing through the cooling tank 168 and the pipe 172. The switching valve 170 is also connected to a pipe 174 connected to the storage container 115.

The switching valve 170 is switchable to the side of the raw material part 110 via the pipe 174 and the side of the collecting part 180 via the pipe 172. Here, the solvent containing the graphene sheet composition to be discharged is repeatedly introduced into the pipe 125 via the pipe 174, and the process is repeated and sent to the pump 130. Repeat steps (a) to (c) continuously.

When the graphene sheet composition is produced using the apparatus 100 for producing a graphene sheet composition, first, the solvent 120 in which the graphite is dispersed in the storage container 115 is supplied to the supercritical processor 155 by the pump 130. The flow rate of the graphite-dispersed solvent 120 supplied to the supercritical processor 155 is, for example, 10 mL/min.

The supercritical processor 155 is set to a temperature and pressure as if the solvent were in a supercritical state. Therefore, the solvent supplied to the supercritical processor 155 rapidly becomes a supercritical state. By the action of the solvent in the supercritical state, at least a part of the graphite, the interlayer bonding thereof is cut, and is peeled off into a graphene-containing graphene sheet composition.

This phenomenon is promoted by the vibration caused by the vibration means 160.

Further, the flow rate in the supercritical processor 155 in which the graphite solvent 120 is dispersed is, for example, 10 mL/min.

Next, the solvent after the supercritical treatment returns to a non-supercritical state, and the solvent containing the graphene sheet composition is discharged from the supercritical processor 155 via the pipe 165. The discharged solvent containing the graphene sheet composition is rapidly cooled to room temperature in the cooling bath 168 through the pipe 165.

Next, the discharged solvent containing the graphene sheet composition is passed through the switching valve 170 and flows through the pipe 174 to return to the storage container 115. Thereafter, the above-described supercritical treatment can be repeated again without repeating the steps (a) to (c). Repeat the supercritical treatment each time, Increase the amount of graphene formed in the solvent.

After the supercritical treatment is repeated only a desired number of times, the solvent containing the graphene sheet composition discharged from the supercritical processor 155 is supplied to the piping 172 by the switching valve 170. Thereby, the solvent containing the graphene sheet composition is recovered by the container 185 of the recovery unit 180 via the pipe 172.

By such a method, for example, a graphene sheet composition containing graphene as a main component can be produced.

The content of graphene in the graphene sheet composition is usually 10% or more, preferably 30% or more and less than 100%.

In addition, the graphene sheet composition preferably contains graphene in a range of 30% or more and less than 100% in consideration of a negative electrode active material for a lithium ion secondary battery, a conductive auxiliary agent, and a resin composite material to be described later. As a main component. A graphene sheet composition obtained by treating graphite in a supercritical fluid.

The content of graphene in the graphene sheet composition is more preferably 50% or more and less than 100%, particularly preferably 70% or more and less than 100%. If the content of graphene in the graphene sheet composition is less than 10%, the characteristics of graphene cannot be exhibited in the graphene sheet composition.

The graphene sheet composition may contain, for example, 30% or more of graphene as a main component, and optionally a material containing 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets. .

2 to 3 layers of graphene sheets in the graphene sheet composition, The content of the graphene sheets of 4 to 6 layers and/or the graphene sheets of 7 or more layers is usually 70% or less, preferably 50% or less, more preferably 30% or less.

The graphene sheet composition preferably has a small number of laminations and a large content of graphene sheets.

The content of the graphene sheets of 7 or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, still more preferably 2% or less, and particularly preferably 0%. When the content of the graphene sheets of 7 or more layers exceeds 15% in the graphene sheet composition, the characteristics of graphene cannot be exhibited.

Further, the apparatus 100 for manufacturing a graphene sheet composition is merely an example, and a graphene sheet composition can be produced by using a device for producing a graphene sheet composition having another structure.

(First embodiment of lithium ion secondary battery)

The negative electrode active material contains a graphene sheet composition, and the graphene sheet composition contains graphene as a main component in a range of 30% or more and less than 100%. A graphene sheet composition obtained by treating graphite in a supercritical fluid.

The content of graphene in the graphene sheet composition is preferably 50% or more and less than 100%, more preferably 70% or more and less than 100%. When the content of graphene in the graphene sheet composition is less than 30%, the storage performance due to graphene having low defects and high crystallinity cannot be obtained, and the discharge capacity and rapid charge and discharge of the lithium ion secondary battery are lowered. characteristic.

The negative electrode active material may further contain a carbon material as needed in order to obtain a desired charge/discharge capacity or battery characteristics.

The carbon material is not particularly limited, and examples thereof include graphite materials such as artificial graphite, thermally decomposed graphite, expanded graphite, natural graphite, scaly graphite, and flaky graphite, easily graphitizable carbon, non-graphitizable carbon, and glassy A carbonaceous material such as carbon, amorphous carbon, or low-temperature fired carbon, which is not developed.

The content of the graphene sheet composition in the negative electrode active material is usually 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more.

In addition, when the negative electrode active material further contains a carbon material, the content of the carbon material in the negative electrode active material is usually 70% by mass or less, preferably 50% by mass or less.

The graphene sheet composition may contain, for example, 30% or more of graphene as a main component, and further optionally arbitrarily contains 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets. s material.

The content of the graphene sheet of 2 to 3 layers, the graphene sheet of 4 to 6 layers, and/or the graphene sheet of 7 or more layers in the graphene sheet composition is usually 70% or less, preferably 50% or less. More preferably 30% or less.

The graphene sheet composition preferably has a small number of laminations and a large content of graphene sheets.

More than 7 layers of graphene sheets in the graphene sheet composition The content is usually 15% or less, preferably 10% or less, more preferably 5% or less, still more preferably 2% or less, and particularly preferably 0%. When the content of the graphene sheets of 7 or more layers in the graphene sheet composition exceeds 15%, the high adsorptivity/release property of the graphene in the anode active material with lithium ions is lowered, and the lithium ion secondary battery is lowered. Discharge capacity and rapid charge and discharge characteristics.

The graphene sheet composition can be produced by the above-described method for producing a graphene sheet composition.

The graphene and the graphene sheet (graphene sheet composition) produced by the method for producing a graphene sheet composition described above are manufactured without passing through graphite oxide, and therefore have a structure having few defects of a pentagon or a heptagonal cell. And excellent in electrochemical stability.

Further, the graphene sheet composition contains graphene in an amount of 30% or more and less than 100%, and contains an N-layer graphene sheet, and therefore can be suitably used as a negative electrode active material.

The lithium ion secondary battery is formed into various shapes such as a cylindrical shape, an angular shape, a button type, or a sheet type, including, for example, a positive electrode, an electrolytic solution, a separator, and a negative electrode.

The negative electrode constituting the lithium ion secondary battery has a current collector and a negative electrode layer covering the current collector.

The negative electrode layer contains a negative electrode active material, a conductive auxiliary material, and a secondary material.

The current collector is not particularly limited, and examples thereof include a nickel foil, a copper foil, a nickel mesh, and a copper mesh.

The negative electrode layer can be formed, for example, by applying a paste in which a negative electrode active material, a conductive auxiliary material, a binder, and a solvent are kneaded to a current collector, followed by drying.

The solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), isopropyl alcohol, and water.

Here, when a binder using water as a solvent is used, it is preferred to use a tackifier in combination.

The amount of the solvent added is adjusted to be as good as the paste is applied to the current collector.

The coating method of the paste is not particularly limited.

The thickness of the negative electrode layer is usually 50 to 200 μm. When the thickness of the negative electrode layer becomes too large, the negative electrode sheet cannot be accommodated in the standardized battery container.

The thickness of the negative electrode layer can be adjusted by the amount of the paste applied.

Further, the thickness of the negative electrode layer can be adjusted by press molding after drying the paste.

Examples of the method of performing press molding include a roll press method, a press method, and the like.

The pressure at the time of press molding is usually from about 100 to about 300 MPa (about 1 to 3 ton/cm ² ).

The conductive auxiliary agent is not particularly limited as long as it can impart conductivity and electrode stability to the negative electrode (a buffering action for volume change of adsorption and desorption of lithium ions), and examples thereof include gas phase carbon fibers (for example, VGCF (made by Showa Denko KK), conductive carbon (for example, DENKA BLACK (manufactured by Electric Chemical Industry Co., Ltd.), Super C65, Super C45, KS6L (above, TIMCAL)).

The mass ratio of the conductive auxiliary agent for the negative electrode active material is usually 0.1 to 1.

The material to be subsequently used is not particularly limited, and examples thereof include polyethylene, polypropylene, ethylene propylene terpolymer, butadiene rubber, styrene butadiene rubber, butyl rubber, acrylic rubber, and polymers having a large ion conductivity. Compounds, etc.

Examples of the polymer compound having a large ion conductivity include polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphosphazene, and polyacrylonitrile.

The mass ratio of the binder of the negative electrode active material is usually 0.005 to 1.

On the other hand, the positive electrode constituting the lithium ion secondary battery has a current collector and a positive electrode layer covering the current collector.

The current collector is not particularly limited, and examples thereof include a nickel foil, an iron foil, a stainless steel foil, a titanium foil, and an aluminum foil.

The positive electrode layer, for example, contains a positive electrode active material, a conductive auxiliary material, and a secondary material.

The positive electrode active material is not particularly limited, and examples thereof include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , V ₂ O ₅ , TiS, and MoS.

The spacer is not particularly limited, but it can be cited as: A non-woven fabric, a fabric, a microporous film containing an olefin such as an olefin or a polypropylene as a main component, or the like.

Further, a polymer electrolyte or the like can also be used as the spacer.

The electrolyte, for example, a solution in which an electrolyte is dissolved in an aprotic solvent.

The aprotic solvent is not particularly limited, and examples thereof include propylene carbonate, ethylene carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, and dioxolane. (dioxolane), 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethylhydrazine, dioxane, 1,2-dimethoxyB Alkane, cyclobutyl hydrazine, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl carbonate Butyl ester, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, diethylene glycol, dimethyl ether, etc. may be used in combination of two or more.

The electrolyte system is not particularly limited as long as it is a lithium salt, and examples thereof include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, and LiC ₄ F ₉ SO. ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _2x+1 SO ₂ ) (C _y F _2y+1 SO ₂ ) (however, x, y are natural numbers), LiCl, LiI, etc. Use two or more.

It is also possible to add a small amount of a substance which is decomposed at the time of initial charging in the electrolytic solution.

The substance to be decomposed at the time of initial charge is not particularly limited, and examples thereof include a carbonic acid extending vinyl ester, a biphenyl group, and a propane sultone.

The content of the substance which is decomposed at the time of initial charge in the electrolytic solution is usually 0.01 to 5% by mass.

Fig. 3 shows an example of a lithium ion secondary battery.

The lithium ion secondary battery 1 is called a cylindrical type, and has a sheet-shaped negative electrode 2, a sheet-like positive electrode 3, a spacer 4 disposed between the negative electrode 2 and the positive electrode 3, and an impregnated negative electrode 2 and a positive electrode 3. The electrolyte of the spacer 4, the cylindrical battery container 5, and the sealing member 6 that seals the battery container 5. In the lithium ion secondary battery 1, the negative electrode 2, the positive electrode 3, and the separator 4 are stacked, and are housed in the battery container 5 in a state in which they are wound.

A battery comprising a plurality of lithium ion secondary batteries 1 is particularly referred to as a battery pack. The battery pack is configured by connecting two or more lithium ion secondary batteries in series and/or in parallel. Thereby, the capacity and voltage of the battery pack can be freely adjusted.

Lithium-ion secondary batteries are used in lighting power sources, machinery, and agricultural equipment for residential power sources such as buildings, houses, and tents, fluorescent lamps, LEDs, organic ELs, street lamps, indoor lighting, and signal conditioners. Power supply for power supply, furniture, toys, accessories, power supplies for mobile phones, mobile appliances, mobile phones, mobile phones, mobile phones, mobile phones, mobile phones, mobile phones, mobile phones, mobile phones, mobile phones, mobile phones, etc. Use for outdoor power supplies, teaching materials, flower making, objects, power supplies for heart rate adjusters, power supplies for heating and coolers with peltier elements, etc. for kanbans, cooling boxes, outdoor generators, etc. .

(Second embodiment of lithium ion secondary battery)

The second embodiment of the lithium ion secondary battery is the same as the first embodiment of the lithium ion secondary battery except for the negative electrode active material.

The negative electrode active material contains a graphene sheet composition and metal particles capable of adsorbing and desorbing lithium ions, and the graphene sheet composition contains graphene as a main component in a range of 30% or more and less than 100%. A graphene sheet composition obtained by treating graphite in a supercritical fluid.

The content of graphene in the graphene sheet composition is preferably 50% or more and less than 100%, more preferably 70% or more and less than 100%. If the content of graphene in the graphene sheet composition is less than 30%, the storage performance due to graphene with low defects and high crystallinity and the accompanying adsorption and desorption of lithium ions by metal particles cannot be obtained. The stress relaxation effect of the volume change caused by the expansion and contraction of the charge and discharge process reduces the discharge capacity and the rapid charge and discharge characteristics of the lithium ion secondary battery. That is, the stress relaxation effect of the large volume change of the metal particles capable of adsorbing and desorbing lithium ions is reduced by the inclusion of the plurality of graphenes (or sandwiching), thereby causing absorption due to the charging and discharging cycle. The effect of internal stress, strain, and the like due to volume expansion/contraction of the large negative electrode active material which occurs in the middle is reduced.

The negative electrode active material can adjust the composition of the graphene sheet at an arbitrary content in order to obtain a desired charge and discharge capacity or battery characteristics. It is used as a material and a metal particle capable of adsorbing and desorbing lithium ions.

Further, the negative electrode active material may further contain a carbon material as needed in order to obtain a desired charge/discharge capacity or battery characteristics.

The carbon material is not particularly limited, and examples thereof include graphite materials such as artificial graphite, thermally decomposed graphite, expanded graphite, natural graphite, scaly graphite, and flaky graphite, easily graphitizable carbon, non-graphitizable carbon, and glassy A carbonaceous material such as carbon, amorphous carbon (carbon), or low-temperature fired carbon, which is not developed.

The content of the graphene sheet composition in the negative electrode active material is usually 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more.

The content of the metal particles in the negative electrode active material is usually from 1 to 70% by mass, preferably from 10 to 70% by mass, and more preferably from 30 to 70% by mass.

In addition, when the negative electrode active material further contains a carbon material, the content of the carbon material in the negative electrode active material is usually 70% by mass or less, preferably 50% by mass or less.

The graphene sheet composition may contain, for example, 30% or more of graphene as a main component, and further optionally arbitrarily contains 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets. s material.

2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and/or 7 or more layers of graphene sheets in the graphene sheet composition The amount is usually less than 70%, preferably less than 50%, more preferably less than 30%.

The graphene sheet composition preferably has a small number of laminations and a large content of graphene sheets.

The content of the graphene sheets of 7 or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, still more preferably 2% or less, and particularly preferably 0%. When the content of the graphene sheets of 7 or more layers in the graphene sheet composition exceeds 15%, the high adsorptivity/release property of the graphene in the anode active material with lithium ions is lowered, and the lithium ion is reduced twice. The discharge capacity and rapid charge and discharge characteristics of the battery.

The graphene sheet composition can be produced by the above-described method for producing a graphene sheet composition.

Since graphene and graphene sheets produced by the method for producing a graphene sheet composition described above are produced without passing through graphite oxide, they have a structure having few defects of pentagonal or heptagonal cells, and are excellent in electrochemical stability.

In addition, the graphene sheet composition contains graphene in a range of 30% or more and less than 100%, and contains an N-layer graphene sheet. Therefore, it can be suitably used as a negative electrode active material.

The material constituting the metal particles capable of adsorbing and desorbing lithium ions is not particularly limited as long as it is a metal capable of adsorbing and desorbing lithium ions, and examples thereof include cerium (Si), aluminum (Al), tin (Sn), and cerium ( Ge), bismuth (Sb), bismuth (Bi), zinc (Zn), or the like may be used in combination of two or more. Among them, Jia is bismuth (Si), aluminum (Al), and tin (Sn).

The metal particles capable of adsorbing and desorbing lithium ions are particles containing a metal element and contain an alloy. Further, the metal particles capable of adsorbing and desorbing lithium ions may partially contain oxides, nitrides, carbides, phosphides, and sulfides. Further, in the metal particles capable of adsorbing and desorbing lithium ions, a solid solution containing a metal element, a eutectic mixture, and an intermetallic compound are also contained.

The particle diameter of the metal particles capable of adsorbing and desorbing lithium ions is usually 0.01 to 100 μm, preferably 0.03 to 10 μm.

Further, in the specification and the patent application, the particle diameter of the metal particles means the primary particle diameter.

The metal particles are not particularly limited as long as they are in the form of particles, and examples thereof include a pulverized product containing a metal element and spherical particles containing a metal element.

The mass ratio of the metal particles capable of adsorbing and desorbing lithium ions to the graphene sheet composition is usually 0.01 to 1, preferably 0.1 to 1. If the mass ratio of the metal particles capable of adsorbing and desorbing lithium ions to the graphene sheet composition is less than 0.01, the effect of adding metal particles having a high discharge capacity may not be exhibited, and if it exceeds 1, the graphene may be present. The composition cannot alleviate the volume change or the strain and stress in the negative electrode layer accompanying the large expansion/contraction in the adsorption and desorption of lithium ions.

(conductive additive)

Conductive additive containing graphene sheet composition, graphene sheet group The adult system contains graphene as a main component in a range of 30% or more and less than 100%. A graphene sheet composition obtained by treating graphite in a supercritical fluid.

The content of graphene in the graphene sheet composition is preferably 50% or more and less than 100%, more preferably 70% or more and less than 100%. If the content of graphene in the graphene sheet composition is less than 30%, the conductivity due to graphene with low defects and high crystallinity cannot be obtained, and the discharge capacity and rapid charge and discharge of the lithium ion secondary battery are lowered. characteristic.

The conductive auxiliary agent may further contain a known carbon material such as carbon black as needed in order to obtain a desired charge/discharge capacity or battery characteristics.

The content of the graphene sheet composition in the conductive auxiliary agent is usually 30% by mass or more, preferably 50% by mass or more, and more preferably 70% by mass or more.

Further, when the conductive auxiliary agent further contains a carbon material other than the graphene sheet composition, the content of the carbon material in the conductive auxiliary agent is usually 70% by mass or less, preferably 50% by mass or less, more preferably 30% by mass. %the following.

The graphene sheet composition may contain, for example, 30% or more of graphene as a main component, and further optionally arbitrarily contains 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets. s material.

2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and/or 7 or more layers of graphene sheets in the graphene sheet composition The amount is usually 70% or less, preferably 50% or less, more preferably 30% or less.

The graphene sheet composition preferably has a small number of laminations and a large content of graphene sheets.

The content of the graphene sheets of 7 or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, still more preferably 2% or less, and particularly preferably 0%. When the content of the graphene sheets of 7 or more layers in the graphene sheet composition exceeds 15%, the conductivity of the graphene in the conductive auxiliary agent is lowered, and when it is applied to the negative electrode of the lithium ion secondary battery, there is a discharge. The capacity and rapid charge and discharge characteristics are reduced.

The graphene sheet composition contains graphene in an amount of 30% or more and less than 100%, and contains N-layer graphene sheets, and therefore can be suitably used as a conductive auxiliary.

Further, the conductive auxiliary agent can be applied to an electrode of a battery such as a lithium ion secondary battery.

When the conductive auxiliary agent is applied to the negative electrode of the lithium ion secondary battery, the mass ratio of the conductive auxiliary agent to the negative electrode active material is usually 0.1 to 1.

(resin composite)

The resin composite material contains a graphene sheet composition, a synthetic resin, and a graphene sheet composition containing graphene as a main component in a range of 30% or more and less than 100%. Graphene sheet composition, in the super It is obtained by treating graphite in a boundary fluid.

The content of graphene in the graphene sheet composition is preferably 50% or more and less than 100%, more preferably 70% or more and less than 100%. If the content of graphene in the graphene sheet composition is less than 30%, the high conductivity of graphene having low defects and high crystallinity cannot be obtained, and the conductivity of the resin composite material is lowered.

The content of the graphene sheet composition in the resin composite material is usually from 0.1 to 95% by mass, preferably from 1 to 70% by mass, more preferably from 5 to 50% by mass. When the content of the graphene sheet composition in the resin composite material is less than 0.1% by mass, the electrical conductivity or thermal conductivity of the resin composite material is lowered, and the practical use range is extremely limited.

The graphene sheet composition may contain graphene as a main component in a range of 30% or more and less than 100%, and further optionally include 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 layers. The material of the above graphene sheet.

The content of 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and/or 7 or more layers of graphene sheets in the graphene sheet composition is usually 70% or less, preferably 50% or less, and more preferably Good is less than 30%.

The graphene sheet composition preferably has a small number of laminations and a large content of graphene sheets.

The content of the graphene sheets of 7 or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, still more preferably 2% or less, and particularly preferably 0%. Graphene sheet group When the content of the graphene sheets of 7 or more layers in the product exceeds 15%, the conductivity of the resin composite material may be lowered.

The graphene sheet composition can be produced by the above-described method for producing a graphene sheet composition.

Since graphene and graphene sheets produced by the method for producing a graphene sheet composition described above are produced without passing through graphite oxide, they have a structure having few defects of pentagonal or heptagonal cells, and can impart high conductivity.

In addition, the graphene sheet composition contains graphene as a main component in a range of 30% or more and less than 100%, and contains an N-layer graphene sheet, and therefore, it can be suitably used as a carbon material filler for a resin composite material. .

The synthetic resin is not particularly limited, but is agglomerated with polyethylene, polypropylene, an ethylene-α-olefin copolymer, a propylene-α-olefin copolymer, an ethylene-vinyl acetate copolymer, and an ethylene-methyl methacrylate copolymer. An olefin-based resin, a graft-modified polyolefin resin such as polyethylene, a polypropylene or an ethylene-propylene copolymer modified by grafting an unsaturated dicarboxylic acid or an anhydride thereof, polystyrene or an AS resin, A styrene resin such as ABS resin, a vinyl chloride resin such as polyvinyl chloride or polyvinylidene chloride, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, or a poly a polyether resin such as acetal or polyphenylene ether; an acrylic resin such as polymethyl methacrylate or polymethacrylate; a fluorine resin such as polyvinylidene fluoride; polycarbonate or polyphenylene sulfide; A thermoplastic resin such as polyfluorene, polyether oxime or polyether ether ketone may be used in combination of two or more kinds. Among them, a polyacetal tree is preferred Fat, polyphenylene ether, polycarbonate, ABS resin.

The resin composite material may further contain additives such as a softener (plasticizer), a foaming agent, a crosslinking agent, a coloring agent, an antioxidant, a dispersing agent, a flame retardant, an ultraviolet ray inhibitor, a lubricant, and the like, as needed.

The method for producing the resin composite material is not particularly limited, and examples thereof include a method of uniformly mixing a synthetic resin and a graphene sheet composition in a well-known mixer.

Further, the resin composite material can be produced by forming a master batch containing a graphene sheet composition and a synthetic resin, and then molding it using a mixer.

The mixer is not particularly limited, and examples thereof include a single-axis extruder, a twin-shaft extruder, a Banbury mixer, a Henschel mixer, a PLASTOMILL, a roll forming machine, and the like. .

The resin composite material can be applied to a conductive material for electromagnetic wave shielding, a conductive connecting material, an outer casing material such as various electronic parts, and various industrial products.

Further, the resin composite material can be used for various industrial products and the like which require anisotropy of conductivity or thermal conductivity. For example, by mixing (kneading) a synthetic resin such as a binder resin, an adhesive/adhesive agent, and a graphene sheet composition, it can be used as an anisotropic conductive sheet, an anisotropic conductive film, an anisotropic conductive coating, or a different material. It is used for an anisotropic conductive material such as a conductive adhesive, an anisotropic conductive adhesive, an anisotropic conductive paste, or an anisotropic conductive ink. Anisotropic conductive materials, generally speaking, are suitable for electronic computers such as personal computers, personal digital assistants, mobile phones, LCD TVs, etc. The plurality of adjacent substrates are connected to each other, or small electronic components such as semiconductor elements are electrically connected to the substrate. Further, the anisotropic conductive material is pressed by being sandwiched between the opposing substrates or the electrode terminals, and is applied to all of the anisotropic conductors or the heat conductors.

The method for producing the anisotropic conductive material is not particularly limited, and examples thereof include adding a graphene sheet composition at an arbitrary concentration to an insulating binder resin or an insulating adhesive/adhesive agent, and uniformly mixing and dispersing them. Method etc.

A method of producing a conductive anisotropic sheet or a conductive anisotropic film will be described as an example. The insulating adhesive resin or the insulating adhesive/adhesive is heated and melted or dissolved in an organic solvent, and after having fluidity, the graphene sheet composition is introduced and uniformly mixed, and when necessary, fluidity is required. The graphene sheet composition is oriented. Thereafter, the binder resin or the adhesive/adhesive is hardened. Further, an anisotropic conductive sheet can be produced by an extrusion method, and an anisotropic conductive film can be produced by a calender molding method or a casting method.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the invention is not limited to the examples. In addition, parts means parts by mass.

(Example 1)

A device for manufacturing a graphene sheet composition of a continuous flow method (refer to Fig. 1), and manufacturing a graphene sheet composition under the following conditions Things.

First, a graphite dispersion containing graphite (manufactured by Aldrich Co., Ltd.) having a particle diameter of 20 μm or less dispersed in a concentration of 1 mg/ml in ethanol for a supercritical fluid is prepared in a storage container 115, and the pump 130 is used at 10 ml/min. The flow rate supplies the graphite dispersion to the supercritical processor 155. The supercritical condition in the supercritical processor 155 is 420 ° C, 12 MPa, and the residence time of the dispersion in the supercritical processor 155 (the time from the inlet to the time of discharge from the outlet) is set to about 1.3 minutes. Let the liquid flow. Ultrasonic vibration is applied from the outside to the supercritical processor 155. The ethanol dispersion discharged from the supercritical processor 155 is cooled to room temperature and atmospheric pressure in the cooling tank 168 via the pipe 165, and then continuously supplied to the supercritical processor 155 under the same conditions using the pump 130. At this time, the discharged ethanol dispersion is stored in the storage tank 115 in a specific amount, and the solvent is supplied to the supercritical processor 155 discontinuously. The number of repetitions of supplying the solvent to the supercritical processor 155 was set to three times. At this time, the time required for the supercritical treatment is 4 minutes.

The dispersion liquid subjected to the supercritical treatment was sent to a vessel 185, and the solvent was distilled off, followed by vacuum drying to obtain a powdery graphene sheet composition. Further, before the solvent was distilled off, centrifugation was carried out under specific conditions to separate and remove the graphite exfoliate in which the number of layers of graphite or graphene of the raw material exceeded 20 layers. Graphene sheet composition, no graphene is detected, 2 to 3 layers of graphene sheets are 15%, 4 to 6 layers of graphene sheets are 60%, and 7 or more layers of graphene sheets are present. It is 25%.

(Example 2)

A powdery graphene sheet composition was obtained in the same manner as in Example 1 except that the number of supercritical treatments was changed to six. At this time, the time required for the supercritical treatment is 8 minutes. Graphene sheet composition, no graphene was detected, and the content of graphene sheets of 2 to 3 layers was 45%, and the content of graphene sheets of 4 to 6 layers was 35%, and graphene sheets of 7 or more layers were used. The content is 20%.

(Example 3)

A powdery graphene sheet composition was obtained in the same manner as in Example 1 except that the number of supercritical treatments was changed to 12 times. At this time, the time required for the supercritical treatment is 16 minutes. Graphene sheet composition, graphene content is 35%, and 2-3 layers of graphene sheets are 30%, 4-6 layers of graphene sheets are 21%, and 7 or more layers of graphene The content of the flakes was 14%.

After measuring the thickness [nm] of any 30 parts of the graphene sheet composition by SPM (scanning probe microscope) Agilent 5500 (manufactured by TOYO TECHNICA Co., Ltd.), it was found that the graphene content was 2 to 20 layers of each layer of graphene. The content of the flakes is more.

Figure 4 is a TEM photograph showing a graphene sheet composition. According to Fig. 4, the end faces of graphene were observed.

(Example 4)

A powdery graphene sheet composition was obtained in the same manner as in Example 1 except that the number of supercritical treatments was 48. At this time, the time required for the supercritical treatment was 62 minutes. The graphene sheet composition had a graphene content of 90%, and the 2-3 layer graphene flakes had a content of 10%, and four or more graphene sheets were not detected.

After measuring the thickness [nm] of any 30 parts of the graphene sheet composition by SPM (scanning probe microscope) Agilent 5500 (manufactured by TOYO TECHNICA Co., Ltd.), it was found that the graphene content was respectively higher than that of the two layers of graphene sheets. The content and the content of the graphene flakes of the three layers are more.

(composition of graphene sheet composition)

The composition of the graphene sheet compositions of Examples 1 to 4 was measured using a laser Raman spectrophotometer (XploRA Raman microscope, manufactured by HORIBA Jobin Yvon) having an excitation wavelength of 532 nm, and was estimated based on the position of 2D-Band. At this time, the measurement point on the measurement substrate is set to 30 dots, and is arbitrarily selected.

Fig. 5 is a graph showing the results of evaluation of the compositions of the graphene sheet compositions of Examples 1 to 4.

(particle size distribution of graphene sheet composition)

After measuring the particle size distribution of the graphene sheet compositions obtained in Examples 1 to 4 using a laser diffraction apparatus Shimadzu SalD-700 (manufactured by Shimadzu Corporation), it was observed that the median diameter (D50) was in the range of several tens nm to 200 nm. range Nano particles.

(Production of lithium ion secondary battery 1-1)

Using the graphene sheet composition of Example 3 as a negative electrode active material, a lithium ion secondary battery 1-1 was produced by the following method.

First, 80 parts of a graphene sheet composition, 10 parts of polyvinylidene fluoride (commercial product) as an adhesive, and 10 parts of carbon black (commercial product) as a conductive auxiliary agent are weighed, and an appropriate amount of N is added thereto. Methyl-2-pyrrolidone (NMP) was stirred and mixed to prepare an electrode paste for a negative electrode.

Next, the negative electrode paste was applied onto a copper foil having a thickness of 20 μm at a thickness of about 100 μm by a doctor blade method, and then vacuum-dried at 80 ° C overnight to obtain a negative electrode layer. Further, the negative electrode layer was used by cutting a cylindrical shape having a diameter of 15 mm by a hand press. On the other hand, a lithium foil having a thickness of 0.5 mm was cut into a cylindrical shape having a diameter of 15 mm to obtain a positive electrode layer.

A porous film (commercial product) made of polypropylene having a thickness of 25 μm was prepared as a separator. Further, in an aprotic solvent in which 30% by volume of ethylene carbonate and 70% by volume of methyl ethyl carbonate were mixed, LiPF ₆ as an electrolyte was dissolved at a concentration of 1 mol/dm ³ to prepare an electrolytic solution.

Using a negative electrode layer, an electrolytic solution, a positive electrode layer, and a separator, a lithium ion secondary battery 1-1 of a 2032 type button cell having a diameter of 20 mm and a thickness of 3.2 mm was produced.

(Production of lithium ion secondary battery 1-2)

A lithium ion secondary battery 1-2 was produced in the same manner as in the production of the lithium ion secondary battery 1-1 except that graphite having a particle diameter of 20 μm or less (manufactured by Aldrich Co., Ltd.) was used as the negative electrode active material.

(Production of Lithium Ion Secondary Battery 1-3)

Graphite having a particle diameter of 20 μm or less (manufactured by Aldrich Co., Ltd.) is oxidized with concentrated sulfuric acid, sodium nitrate, and potassium permanganate according to the well-known Hummers method (US Pat. No. 2, 798, 878, July 9, 1957) at about 400. The obtained graphite oxide was subjected to heat treatment reduction in a non-oxidizing atmosphere at ° C to obtain a reduced body of powdered graphite oxide.

A lithium ion secondary battery 1-3 was produced in the same manner as in the production of the lithium ion secondary battery 1-1, except that the obtained reduced form of the graphite oxide was used as the negative electrode active material.

Next, using a lithium ion secondary battery 1-1 to 1-3, a charge and discharge test was performed at 25 °C.

(charge and discharge test)

The charge and discharge test was carried out by charging the battery potential from a stationary potential to a constant current of 20 mV and discharging it to 1.5 V at a constant current.

The current value was set to a nominal capacity value of 372 mAh/g, and the C rate was set to 0.1 C at the time of charge and discharge. However, 0.1C refers to charging a cell having a capacity having a nominal capacity value at a constant current, and then discharging it to become a current value at which charging and discharging are completed in 10 hours. Measure the first cycle of the battery The discharge capacity of the ring (initial discharge capacity). In addition, the C rate generally indicates the current value of charge and discharge of the battery, and is expressed by C rate = current value (A) / capacity (Ah). When the battery having a capacity of 1 Ah was charged and discharged at 1 A, it was expressed as 1 C, and when charged and discharged at 10 A, it was expressed as 10C.

In order to evaluate the rapid charge and discharge characteristics, the C rate was set to 1 C, 2 C, and 5 C in the same manner as described above, and the discharge capacity (initial discharge capacity) of the first cycle of the battery was measured at the C rate. The value obtained by dividing the discharge capacity of the first cycle of 1C, 2C, and 5C by the discharge capacity of 0.1 C was determined as the discharge capacity retention ratio.

Table 1 shows the evaluation results of the charge and discharge tests of the lithium ion secondary batteries 1-1 to 1-3.

According to Table 1, the lithium ion secondary battery 1-1 is excellent in primary discharge capacity and discharge capacity retention.

On the other hand, in the lithium ion secondary battery 1-2, since graphite is used as the negative electrode active material, the initial discharge capacity and the discharge capacity retention ratio are lowered.

Further, in the lithium ion secondary battery 1-3, since the reduced body using graphite oxide is used as the negative electrode active material, the initial discharge capacity and the discharge capacity retention ratio are lowered. Here, the reduced form of the graphite oxide remains even if a part of the reduced oxygen functional group is thermally treated, and is a defect other than the hexahedral structure accompanying the detachment of the oxygen functional group (hydroxy group, epoxy group, carboxyl group, etc.). There are many structures remaining, and therefore, the potential flat region of the charge and discharge curve is lacking.

(Production of lithium ion secondary battery 2-1)

Using the graphene sheet composition of Example 3 and ruthenium particles (manufactured by Aldrich Co., Ltd.) having a particle diameter of 100 nm or less as a negative electrode active material, a lithium ion secondary battery 2-1 was produced by the following method.

First, weighed 72 parts of a graphene sheet composition, 8 parts of cerium particles, 10 parts of polyvinylidene fluoride (commercial product) as an adhesive, and 10 parts of carbon black (commercial product) as a conductive auxiliary agent. An appropriate amount of N-methyl-2-pyrrolidone (NMP) was added thereto, and the mixture was stirred and mixed to prepare an electrode paste for a negative electrode.

Lithium ion secondary electricity was produced in the same manner as in the lithium ion secondary battery 1-1 except that the obtained electrode paste for a negative electrode was used. Pool 2-1.

(Production of lithium ion secondary battery 2-2)

A lithium ion secondary battery 2 was produced in the same manner as in the production of the lithium ion secondary battery 2-1 except that graphite having a particle diameter of 20 μm or less (manufactured by Aldrich Co., Ltd.) was used instead of the graphene sheet composition of Example 3. -2.

(Production of Lithium Ion Secondary Battery 2-3)

Graphite having a particle diameter of 20 μm or less (manufactured by Aldrich Co., Ltd.) is oxidized with concentrated sulfuric acid, sodium nitrate, and potassium permanganate according to the well-known Hummers method (US Pat. No. 2, 798, 878, July 9, 1957) at about 400. The obtained graphite oxide was subjected to heat treatment reduction in a non-oxidizing atmosphere at ° C to obtain a reduced body of powdered graphite oxide.

A lithium ion secondary battery 2-3 was produced in the same manner as in the production of the lithium ion secondary battery 2-1 except that the obtained graphene oxide reduced body was used instead of the graphene sheet composition of Example 3.

Next, using a lithium ion secondary battery 2-1 to 2-3, a charge and discharge test was performed at 25 ° C in the same manner as described above.

Table 2 shows the evaluation results of the charge and discharge tests of lithium ion secondary batteries 2-1 to 2-3.

According to Table 2, the lithium ion secondary battery 2-1 is excellent in primary discharge capacity and discharge capacity retention.

On the other hand, in the lithium ion secondary battery 2-2, since graphite and ruthenium particles are used as the negative electrode active material, the initial discharge capacity and the discharge capacity retention ratio are lowered.

Further, in the lithium ion secondary battery 2-3, since the reduced body of the graphite oxide and the ruthenium particles are used as the negative electrode active material, the initial discharge capacity and the discharge capacity retention ratio are lowered. Here, the reduced form of the graphite oxide remains even if a part of the reduced oxygen functional group is thermally treated, and is a defect other than the hexahedral structure accompanying the detachment of the oxygen functional group (hydroxy group, epoxy group, carboxyl group, etc.). There are many structures remaining, and therefore, the potential flat region of the charge and discharge curve is lacking.

(Production of lithium ion secondary battery 3-1)

Using the graphene sheet composition of Example 3 as a conductive auxiliary agent, a lithium ion secondary battery 3-1 was produced by the following method.

First, 72 parts of graphite (manufactured by Aldrich Co., Ltd.) having a particle diameter of 20 μm or less and 8 parts of cerium particles, 10 parts of polyvinylidene fluoride (commercial product) as an adhesive, and a graphene sheet composition are weighed as a negative electrode active material. In 10 parts, an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added thereto, and the mixture was stirred and mixed to prepare an electrode paste for a negative electrode.

A lithium ion secondary battery 3-1 was produced in the same manner as the lithium ion secondary battery 1-1 except that the obtained electrode paste for a negative electrode was used.

Next, using a lithium ion secondary battery 3-1, a charge and discharge test was performed at 25 ° C in the same manner as described above. As a result, the initial discharge capacity of the lithium ion secondary battery 3-1 is equal to the initial discharge capacity of the lithium ion secondary battery 2-2, and the discharge capacity retention rate is improved, in particular, by about 5% at 2C. About 20% at 5C.

(production of tablet 1)

Using the graphene sheet composition of Example 3 as a carbon material filler, the flat plate 1 was produced by the following method.

First, a polyacetal resin DURACON M90 (manufactured by Polyplastics Co., Ltd.) as a synthetic resin was blended with a 10% by mass graphene sheet composition, and after dry blending using a star mixer, it was kneaded in a molten state using an extruder. A flat plate 1 of 100 mm × 100 mm × 2 mm was formed by injection molding. The flat plate 1 was cut to a width of 1 mm, and the resistance was measured by a 4-terminal needle method to be 1.2 × 10 ⁴ Ω.

(production of tablet 2)

A flat plate 2 was produced in the same manner as the flat plate 1 except that graphite having a particle diameter of 20 μm or less (manufactured by Aldrich Co., Ltd.) was used instead of the graphene sheet composition of Example 3. The flat plate 2 was cut out to a width of 1 mm, and the resistance was measured by a 4-terminal needle method to be 5.0 × 10 ⁶ Ω.

(production of tablet 3)

Graphite (manufactured by Aldrich Co., Ltd.) having a particle diameter of 20 μm or less, according to the week Known Hummers method (US Pat. No. 2, 798, 878, July 9, 1957), after oxidation with concentrated sulfuric acid, sodium nitrate and potassium permanganate, the obtained graphite oxide is subjected to heat treatment reduction in a non-oxidizing environment of about 400 ° C. A reduced body of powdered graphite oxide was obtained.

A flat plate 3 was produced in the same manner as the flat plate 1 except that the obtained graphite oxide reduced body was used instead of the graphene sheet composition of Example 3. The flat plate 3 was cut out to a width of 1 mm, and the resistance was measured by a 4-terminal needle method to be 5.7 × 10 ⁶ Ω.

Table 3 shows the evaluation results of the resistance of the plates 1 to 3.

According to Table 3, the conductivity of the flat plate 1 was excellent.

On the other hand, in the flat plate 2, since graphite is used as a carbon material filler, electrical conductivity is lowered.

Further, the flat plate 3 has a reduced conductivity because it uses a reduced body of graphite oxide as a carbon material filler. Here, the reduced form of the graphite oxide remains even if a part of the reduced oxygen functional group is thermally treated, and is a defect other than the hexahedral structure accompanying the detachment of the oxygen functional group (hydroxy group, epoxy group, carboxyl group, etc.). There are many structures remaining, and therefore, there is a lack of a potential flatness region of the charge and discharge curve.

This international application claims priority based on Japanese Patent Application Nos. 2012-265833, 2012-265834, 2012-265835, and 2012-265836, filed on Dec. 4, 2012, the Japanese Patent Application Nos. 2012-265833, 2012-265834, The entire contents of 2012-265835, 2012-265836 are used in this international application.

Claims (20)

A graphene sheet composition characterized by containing graphene as a main component in a range of 30% or more and less than 100%, and treating the graphite in a supercritical fluid. The graphene sheet composition of claim 1, which contains at least 7 layers of graphene sheets of 15% or less. A negative electrode active material for a lithium ion secondary battery, which comprises the graphene sheet composition of claim 1. A negative electrode for a lithium ion secondary battery, which comprises the negative electrode active material for a lithium ion secondary battery according to claim 3. A lithium ion secondary battery characterized by having the negative electrode for a lithium ion secondary battery according to claim 4. A battery pack characterized by having the lithium ion secondary battery as claimed in claim 5. A negative electrode active material for a lithium ion secondary battery, comprising the graphene sheet composition of claim 1 and metal particles capable of adsorbing and desorbing lithium ions. The negative electrode active material for a lithium ion secondary battery according to claim 7, wherein the metal particles contain one or more selected from the group consisting of aluminum, lanthanum and tin. A negative electrode for a lithium ion secondary battery, which comprises the negative electrode active material for a lithium ion secondary battery according to claim 7. A lithium ion secondary battery characterized by having the negative electrode for a lithium ion secondary battery according to claim 9. A battery pack characterized by having a lithium ion secondary battery as claimed in claim 10. A conductive auxiliary characterized by containing the graphene sheet composition of claim 1. An electrode characterized by containing a conductive additive as claimed in claim 12. A battery characterized by having an electrode as claimed in claim 13. A resin composite material comprising the graphene sheet composition of claim 1 and a synthetic resin. A method for producing a graphene sheet composition, comprising: (a) a step of supplying a solvent containing graphite to a supercritical treatment field; (b) causing a solvent supplied to the supercritical treatment field to be supercritical And (c) returning the solvent in the supercritical state to a non-supercritical state, and performing the flow of the solvent in a continuous flow manner in the steps (a) to (c), The steps (a) to (c) are repeated a plurality of times continuously and/or discontinuously. The method for producing a graphene sheet composition according to claim 16, wherein the steps (b) and/or (c) are carried out in a state where vibration is applied. A method of producing a graphene sheet composition according to claim 16, wherein the number of steps (a) to (c) is repeated continuously and/or discontinuously It is 10 times or more and 100 times or less. A device for producing a graphene sheet composition, comprising: (a) means for supplying a solvent containing graphite to a supercritical treatment field; (b) causing a solvent supplied to the supercritical treatment field to be supercritical And (c) means for returning the solvent in the supercritical state to a non-supercritical state, and the means (a) to (c) are performed by continuously flowing the solvent. The apparatus for producing a graphene sheet composition according to claim 19, wherein the means (b) and/or (c) have means for applying vibration.