WO2014087992A1 - 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, an assembled battery, a resin composite material, a method for producing a graphene sheet composition, and a graphene sheet The present invention relates to an apparatus for producing a composition.

Graphene has attracted attention as a carbon material. Perfect graphene consists only of a collection of hexagonal cells, and its electron mobility is surprisingly high at 15000 cm ² V ^-1 S ^-1 at room temperature, with excellent thermal and chemical stability, and a large specific surface area. Due to its features, it is expected to develop many applications such as next-generation electronic materials and power storage applications.

However, if pentagonal or heptagonal cells exist in a set of hexagonal cells, lattice defects occur, and the characteristics expected of graphene cannot be sufficiently extracted. From this point of view, there is a demand for complete graphene consisting only of a set of hexagonal cells.

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

On the other hand, lithium-ion secondary batteries for power storage use have high capacity and can be reduced in size and weight, so they are installed in mobile devices such as mobile phones and notebook computers. These portable devices are required to have higher performance of lithium ion secondary batteries in accordance with higher performance, higher functionality, and expanded applications. Here, the carbon material used as the negative electrode active material of the lithium ion secondary battery is generally roughly divided into a graphite-based carbon material and an amorphous-based carbon material. The graphite-based carbon material has an advantage that the energy density per unit volume is higher than that of the amorphous carbon material. Therefore, in a lithium ion secondary battery for portable equipment that is compact but requires a large charge / discharge capacity, a graphite-based carbon material is generally used as the negative electrode active material.

Graphite has a theoretical discharge capacity value of 372 mAh / g. However, in an actual lithium ion secondary battery, a SEI (solid electrolyte interface) film is formed when lithium ions are inserted for the first time, so that the discharge capacity is 300 mAh. / G only.

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

Recently, as an alternative material for graphite, a metal capable of inserting and extracting lithium ions such as silicon, tin, aluminum, tungsten, etc., which has a high discharge capacity, or an alloy material thereof has been used as a negative electrode active material. For example, in silicon, the theoretical value of discharge capacity is 4199 mAh / g, and in tin, the theoretical value of discharge capacity is 994 mAh / g.

However, these metal / alloy materials have a large volume change rate when lithium ions are inserted, for example, silicon is 4.0 times and tin is 3.6 times, and the volume change rate of graphite is 1. Very large for 1x. In addition, such metal / alloy materials have a large volume change due to the insertion / desorption of lithium ions. Separation occurs at the interface between the material and the current collector, or the metal / alloy material itself is destroyed. For this reason, there is a problem that the discharge capacity is drastically reduced and the cycle characteristics of the lithium ion secondary battery are extremely poor.

Therefore, it has been proposed to mix carbon materials such as graphite and these metal / alloy materials, or to coat them with metal or carbon that does not occlude / release lithium ions.

However, there are problems that irreversible capacity is large, cycle stability is poor, and practical battery cycle performance cannot be satisfied.

Patent Document 2 discloses a negative electrode composite compound for a lithium ion battery mainly composed of nanographene platelets. At this time, the negative electrode composite compound for a lithium ion battery includes a) particles or coatings having a micrometer or nanometer size capable of absorbing and desorbing lithium ions, and b) a plurality of graphene plates having a nanometer size. Prepare with a lett. The graphene platelet is a single-layer graphene sheet or a layer formed by stacking graphene sheets and has a thickness of 100 nm or less. Further, at least the particles or coating are physically or chemically bound to at least one of the graphene platelets. The amount of graphene platelets is 2 to 90% by mass, and the amount of particles or coating is 98 to 10% by mass.

Patent Document 3 discloses a resin composition containing a synthetic resin and exfoliated graphite. At this time, exfoliated graphite is a laminate of graphene sheets, the number of laminations is 150 layers or less, and the aspect ratio is 20 or more.

JP 2009-151956 A Special table 2011-503804 gazette JP 2012-77286 A

2009 Annual Report of National Institute of Advanced Industrial Science and Technology, p. 692

However, the method for producing a graphene sheet of Non-Patent Document 1 is a batch type (batch 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.

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

Also, there is a problem that the conductivity of the resin composition of Patent Document 3 is insufficient.

An object of one embodiment of the present invention is to provide a graphene sheet composition containing graphene as a main component.

An object of one embodiment of the present invention is to provide a negative electrode active material for a lithium ion secondary battery that can improve the discharge capacity and rapid charge / discharge characteristics of the lithium ion secondary battery.

An object of one embodiment of the present invention is to provide a conductive additive capable of improving the discharge capacity and rapid charge / discharge characteristics of a lithium ion secondary battery.

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

An object of one embodiment of the present invention is to provide a method for producing a graphene sheet composition capable of producing a graphene sheet composition containing graphene as a main component in a short time.

An object of one embodiment of the present invention is to provide a graphene sheet composition manufacturing method and a manufacturing apparatus capable of manufacturing a graphene sheet composition in a short time.

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

One embodiment of the present invention includes the above graphene sheet composition in a negative electrode active material for a lithium ion secondary battery.

One embodiment of the present invention includes, in a negative electrode active material for a lithium ion secondary battery, the above graphene sheet composition and metal particles capable of inserting and extracting lithium ions.

One embodiment of the present invention includes the above graphene sheet composition in a conductive additive.

One embodiment of the present invention includes a synthetic resin and the above graphene sheet in a resin composite material.

One embodiment of 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 site; and (b) a solvent supplied to the supercritical processing site. A step of bringing the solvent into a supercritical state; and (c) a step of returning the solvent in the supercritical state to a non-supercritical state. In the steps (a) to (c), the flow of the solvent is a continuous flow system. The steps (a) to (c) are repeated a plurality of times continuously and / or discontinuously.

One aspect of the present invention is an apparatus for producing a graphene sheet composition, wherein (a) a means for supplying a solvent containing graphite to a supercritical processing field, and (b) a supercritical solvent supplied to the supercritical processing field. And (c) means for returning the solvent in the supercritical state to a non-supercritical state, and the means (a) to (c) perform the flow of the solvent in a continuous flow system. .

That is, the present invention provides the following inventions.
(1) containing graphene as a main component in a range of 30% to less than 100%,
A graphene sheet composition obtained by treating graphite in a supercritical fluid.
(2) The graphene sheet composition as described in (1) above, comprising 7 or more layers of graphene sheets at 15% or less.
(3) A negative electrode active material for a lithium ion secondary battery, comprising the graphene sheet composition according to (1) above.
(4) A negative electrode for a lithium ion secondary battery comprising the negative electrode active material for a lithium ion secondary battery as described in (3) above.
(5) A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to (4) above.
(6) A battery pack comprising the lithium ion secondary battery according to (5) above.
(7) A negative electrode active material for a lithium ion secondary battery, comprising the graphene sheet composition according to (1) above and metal particles capable of inserting and extracting lithium ions.
(8) The negative electrode active material for a lithium ion secondary battery according to (7), wherein the metal particles include one or more selected from the group consisting of aluminum, silicon, and tin.
(9) A negative electrode for a lithium ion secondary battery comprising the negative electrode active material for a lithium ion secondary battery as described in (7) above.
(10) A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to (9) above.
(11) A battery pack comprising the lithium ion secondary battery according to (10).
(12) A conductive additive comprising the graphene sheet composition described in (1) above.
(13) An electrode comprising the conductive additive according to (12).
(14) A battery comprising the electrode according to (13).
(15) A resin composite material comprising the graphene sheet composition according to (1) above and a synthetic resin.
(16) (a) supplying a solvent containing graphite to a supercritical processing plant;
(B) bringing the solvent supplied to the supercritical processing plant into a supercritical state;
(C) having a step of returning the solvent in the supercritical state to a non-supercritical state;
In the steps (a) to (c), the solvent is flowed in a continuous flow system,
A method for producing a graphene sheet composition, wherein the steps (a) to (c) are repeated a plurality of times continuously and / or discontinuously.
(17) The method for producing a graphene sheet composition according to (16), wherein the step (b) and / or (c) is performed in a state where vibration is applied.
(18) The graphene sheet composition as described in (16) above, wherein the number of times of repeating the steps (a) to (c) continuously and / or discontinuously is 10 or more and 100 or less Manufacturing method.
(19) (a) means for supplying a solvent containing graphite to a supercritical processing station;
(B) means for bringing the solvent supplied to the supercritical processing plant into a supercritical state;
(C) a means for returning the supercritical solvent to a non-supercritical state;
The apparatus (a) to (c) is an apparatus for producing a graphene sheet composition, wherein the solvent is flowed in a continuous flow system.
(20) The apparatus for producing a graphene sheet composition as described in (19) above, wherein the means (b) and / or (c) has means for applying vibration.

According to one embodiment of the present invention, a graphene sheet composition containing graphene as a main component can be provided.

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

According to one embodiment of the present invention, a conductive additive that can improve the discharge capacity and rapid charge / discharge characteristics of a lithium ion secondary battery can be provided.

According to one embodiment of the present invention, a resin composite material having excellent conductivity can be provided.

According to one embodiment of the present invention, a method for producing a graphene sheet composition capable of producing a graphene sheet composition containing graphene as a main component in a short time can be provided.

According to one embodiment of the present invention, a graphene sheet composition manufacturing apparatus capable of manufacturing a graphene sheet composition in a short time can be provided.

It is a figure which shows roughly an example of the manufacturing method of a graphene sheet composition. It is a figure which shows roughly an example of the manufacturing apparatus of a graphene sheet composition. It is a perspective view which shows an example of a lithium ion secondary battery. 4 is an example of a TEM photograph of the graphene sheet composition of Example 3. It is a figure which shows the evaluation result of the lamination | stacking number of the graphene sheet composition of Examples 1-4.

Next, an embodiment for carrying out the present invention will be described with reference to the drawings.

(Graphene sheet composition and production method and production apparatus thereof)
The method for producing a graphene sheet composition includes (a) a step of supplying a solvent containing graphite to a supercritical processing field, (b) a step of bringing the solvent supplied to the supercritical processing field into a supercritical state, and (c And (b) returning the supercritical solvent to a non-supercritical state. At this time, in the steps (a) to (c), the solvent flow is performed in a continuous flow system, and the steps (a) to (c) are repeated a plurality of times continuously or / and discontinuously. Thereby, compared with the manufacturing method performed by the conventional batch system, the graphene sheet composition with much content of graphene can be manufactured in a short time.

Note that in the present specification and claims, a stacked body in which N layers of graphene are stacked is referred to as an N-layer graphene sheet. N is an integer of 2 to 20.

In the present specification and claims, a composition containing graphene and / or an N-layer graphene sheet is referred to as a graphene sheet composition.

Also, the non-supercritical state refers to, for example, a state that becomes a liquid or a gas at room temperature and normal pressure or at a temperature higher than normal pressure at room temperature.

At this time, the step (b) and / or (c) is preferably performed in a state where vibration is applied.

In the method for producing a graphene sheet composition, the raw material graphite can be partially or completely exfoliated in the supercritical fluid by the step (b) to produce a graphene sheet composition.

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

Note that the steps (a) to (c) are continuously repeated means that the following steps (a) to (c) are performed after the steps (a) to (c) are performed. Means. On the other hand, the steps (a) to (c) are discontinuously repeated means that the solvent containing the graphene sheet composition discharged from the supercritical processing plant after the steps (a) to (c) ( This means that after the dispersion liquid is temporarily guided to the storage container, it is pumped from the storage container and the following steps (a) to (c) are performed. That is, the steps (a) to (c) are discontinuously repeated means that the steps (a) to (c) are performed and then the dispersion is guided to the storage container. And the following steps (a) to (c) are repeated. Further, before performing the steps (a) to (c), the raw material tank storing the solvent containing graphite is used in combination with a storage container that is guided after the steps (a) to (c). The steps (a) to (c) may be repeated.

Thus, in the method for producing a graphene sheet composition, from the step (b) (supercritical state under high temperature and high pressure) to the non-supercritical state under low temperature and low pressure from the step (c) for a short time, By repeatedly pressurizing and releasing, a graphene sheet composition can be effectively generated as compared with a production method performed in a conventional closed container (batch type). For example, in Example 3 in which twelve repetitive treatments are carried out in about 16 minutes, for example, in order to open rapidly from a supercritical treatment site at 420 ° C. and 12 MPa at normal temperature and normal pressure, Heating and cooling can be repeated quickly and rapidly. As a result, the graphite peeling effect is enhanced. Here, in the batch method, if approximately 1 hour / batch processing is performed 12 times, 120 hours are required.

Hereinafter, each step will be described in detail with reference to FIG.

(Process S110)
First, a solvent containing graphite is prepared.

The graphite is not particularly limited, and examples thereof include natural graphite and artificial graphite.

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

Artificial graphite can be produced by firing petroleum heavy oil, coal heavy oil, petroleum coke, coal coke, and pitch carbon fiber at 1500 to 3200 ° C. in a non-oxidizing atmosphere. . At this time, you may bake in presence of graphitization catalysts, such as a boron compound.

Properties of graphite such as purity and crystallinity are not particularly limited.

In the present specification and claims, the particle diameter means the primary particle diameter.

The primary particle diameter d of the particles is determined by the formula S = 6 / ρd after measuring the specific surface area by the BET method.
Can be obtained by conversion. Here, S is the specific surface area of the particles, and ρ is the density of the particles.

In the present specification and claims, the term “solvent” means a liquid or gas that can be converted into a supercritical fluid under normal temperature and normal pressure.

The solvent is not particularly limited, but water, alcohols, ethers, esters, ketones, hydrocarbons, dimethyl sulfoxide, N, N′-dimethylformamide, N, N′-dimethylacetamide, 1-methyl- Examples thereof include liquids such as 2-pyrrolidone, and gases such as carbon dioxide, nitrogen, oxygen, helium, argon, ammonia, nitrous oxide, lower alkanes, and alkenes. Of these, water, methanol, ethanol, dimethyl ether, N, N-dimethylformamide (DMF), 1-methyl-2-pyrrolidone (NMP), and carbon dioxide are preferable.

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

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

Next, the prepared solvent containing graphite is supplied to a supercritical processing place (for example, a reaction tube) for supercritically processing the graphite. In this case, 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 plant using, for example, a pump.

The rate at which the solvent containing graphite is supplied to the supercritical processing site is usually 1 to 1000 mL / min, and preferably 5 to 100 mL / min.

(Process S120)
Next, in the supercritical processing field, the graphite is supercritically processed in an environment where the solvent is in a supercritical state.

For example, when the solvent is ethanol, the critical temperature is 241 ° C. and the critical pressure is 6.1 MPa. For this reason, the supercritical processing field has a temperature of 241 ° C. or higher and a pressure of 6.1 MPa or higher, for example, a temperature of 420 ° C. and a pressure of 12 MPa.

When the solvent is methanol, similarly, the supercritical processing place has a temperature of 240 ° C. or higher and a pressure of 8.1 MPa or higher.

When the solvent is water, similarly, the supercritical processing field has a temperature of 374 ° C. or higher and a pressure of 22.1 MPa or higher.

As described above, the temperature and pressure of the supercritical processing field are set according to the critical temperature and critical pressure of the solvent used.

The time for keeping the solvent in the supercritical state, that is, the time for the graphite to stay in the supercritical fluid is usually 0.5 seconds to 10 minutes.

By treating graphite in a supercritical fluid, at least a part of the graphite is separated into layers by breaking the bond between layers. Thereby, it peels in the graphene sheet composition containing a graphene.

At this time, vibration may be applied to the supercritical processing field as necessary. Thereby, more graphene can be produced | generated.

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

In the method of applying vibration to the supercritical processing field using ultrasonic waves, it is possible to easily apply vibration to the supercritical processing field due to the effects of ultrasonic cavitation, vibration acceleration, straight flow, and the like.

(Step S130)
Next, after the solvent in the supercritical state is returned to the non-supercritical state, the solvent containing the graphene sheet composition is discharged from the supercritical processing site.

The non-supercritical state is usually from room temperature to the boiling point of the solvent and atmospheric pressure.

In the non-supercritical state, vibration may be applied as necessary. Thereby, more graphene can be produced | generated.

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

Next, the solvent (dispersion liquid) containing the graphene sheet composition discharged from the supercritical processing plant is continuously supplied again to the supercritical processing plant, and the second supercritical processing is performed. Thereafter, after the solvent brought into the supercritical state is returned again to the non-supercritical state, the solvent containing the graphene sheet composition is discharged from the supercritical processing place.

(Process S140)
Thereafter, the steps (a) to (c) are repeated.

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

At this time, in order to produce a desired graphene sheet composition, the number of times of repeating the steps (a) to (c) is arbitrarily set. If the number of times of repeating the steps (a) to (c) is extremely large, the time required for producing the graphene sheet composition becomes long and the production cost increases. For this reason, the number of times of repeating steps (a) to (c) is preferably 100 times or less.

Through the above steps, a graphene sheet composition can be generated.

For example, the flow rate of ethanol is 10 ml / min, the input amount of graphite is 10 mg / min, the temperature of the supercritical processing field is 420 ° C., the pressure of the supercritical processing field is 12 MPa, and the graphite in the supercritical processing field is in the supercritical fluid. When the steps (a) to (c) are repeated 12 times under the conditions of processing in a short time, the graphene content in the graphene sheet composition is 35%. Further, when the steps (a) to (c) are repeated 48 times, the graphene content is 90% or more.

The content of each component in the graphene sheet composition is the kind of supercritical fluid, the flow rate at which the solvent containing graphite of (a) is supplied to the heat treatment field, the input amount of graphite, the temperature of the supercritical treatment field, It is designed arbitrarily depending on conditions such as the pressure in the critical processing field, the time that graphite stays in the supercritical processing field, whether or not the storage container is used, and the amount of storage in the storage container.

Thus, in the method for producing a graphene sheet composition, a graphene sheet composition containing graphene as a main component can be generated.

In the present specification and claims, the content [%] of the graphene or the N-layer graphene sheet in the graphene sheet composition is estimated from the position of 2D-Band as measured by Raman scattering spectroscopy. This means the ratio [%] of the number of graphene or N-layer graphene sheets with respect to the total number of graphene and graphene sheets (refer to Chem. Eur. J. 2010, 16, p6488-6494 for 2D-Band position measurement etc.) .

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

For example, when a graphene sheet composition is placed on a sample substrate, 30 positions of 2D-Band are measured by Raman scattering spectroscopy, and 9 or more positions of 2D-Band are less than 2585 cm ⁻¹ , The content of graphene in the sheet composition is 30% or more.

In addition, when the 9-point 2D-Band position is 2685 cm ⁻¹ or more and less than 2695 cm ⁻¹ , the content of the 2 to 3 graphene sheets in the graphene sheet composition is 30%.

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

In addition, the measurement points of Raman scattering spectroscopy may 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% to less than 100%, and other components other than graphene are 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 layers or more of graphene It further includes one or more components selected from the group consisting of sheets.

In the present specification and claims, the term “containing graphene as a main component” means that the content of graphene is higher than the content of graphene sheets in each of 2 to 20 layers.

Here, the content of the graphene and the content of the graphene sheet of each of 2 to 20 layers are determined by using the SPM (scanning probe microscope) method to determine the thickness [nm] at any 30 positions of the graphene sheet composition. It is obtained by measuring.

In addition, you may increase the measurement location of the thickness of a graphene sheet composition to 60 places, 100 places, etc.

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

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

The graphene sheet composition can be purified by separating and removing the graphite exfoliated material having more than 20 layers of graphite and graphene by a separation method by centrifugation or a floating density separation method in a specific dispersion medium. it can.

FIG. 2 schematically shows an example of an apparatus for producing a graphene sheet composition.

The graphene sheet composition manufacturing apparatus 100 includes a raw material unit 110, a supercritical processing unit 150, and a recovery unit 180.

The raw material part 110 is a part for storing a solvent containing graphite as a raw material of the graphene sheet composition. The raw material unit 110 includes a storage container 115, and the storage container 115 contains a solvent 120 (dispersion liquid) in which graphite is dispersed.

The supercritical processing unit 150 is a part that supercritically processes graphite by bringing the solvent into a supercritical state. The supercritical processing unit 150 includes a heat and pressure resistant supercritical processor 155. In addition, the supercritical processing unit 150 includes a vibration unit 160. The vibration means 160 is configured to apply vibration to the supercritical processor 155. However, the vibration means 160 may be omitted.

Between the raw material unit 110 and the supercritical processing unit 150, a pipe 125 that connects the storage container 115 and the supercritical processing unit 155 is provided. A pump 130 is installed in the pipe 125.

The recovery unit 180 is a part that recovers the solvent containing the graphene sheet composition after being supercritically processed by the supercritical processing unit 150. The collection unit 180 includes a container 185. A cooling liquid may be accommodated in the container 185.

A pipe 165 is connected to the outlet side of the supercritical processing section 150, and the pipe 165 is configured to pass through 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 installed immediately before or after the cooling bath 168.

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

The switching valve 170 can be switched between the raw material part 110 side via the pipe 174 and the recovery part 180 side via the pipe 172. Here, the process of (a) to (c) is continuously performed by repeating the process of repeatedly sending the solvent containing the discharged graphene sheet composition to the pipe 125 through the pipe 174 and sending it to the pump 130. Can be repeated.

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

The supercritical processor 155 is set to a temperature and pressure at which the solvent is in a supercritical state. For this reason, the solvent supplied into the supercritical processor 155 quickly enters a supercritical state. Due to the action of the solvent in a supercritical state, at least a part of the graphite is cut off between the layers and peeled off into the graphene sheet composition containing graphene.

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

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

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

Next, the solvent containing the discharged graphene sheet composition is circulated to the pipe 174 by the switching valve 170 and returned to the storage container 115. Thereafter, the supercritical processing described above is repeated again, and the steps (a) to (c) can be repeated discontinuously. Each time the supercritical process is repeated, the content of graphene generated in the solvent increases.

After the supercritical process is repeated a desired number of times, the solvent containing the graphene sheet composition discharged from the supercritical processor 155 is supplied to the pipe 172 by the switching valve 170. Thereby, the solvent containing the graphene sheet composition is recovered in 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, and preferably 30% or more and less than 100%.

In addition, the graphene sheet composition contains graphene as a main component in a range of 30% or more and less than 100% in consideration of application to a negative electrode active material for lithium ion secondary batteries, a conductive additive, and a resin composite material described later. It is preferable. The graphene sheet composition is 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%, and particularly preferably 70% or more and less than 100%. If the graphene content in the graphene sheet composition is less than 10%, the features of graphene are not utilized in the graphene sheet composition.

As the graphene sheet composition, for example, a material containing 30% or more of graphene as a main component, and further including 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets is arbitrarily selected. be able to.

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 and 50% or less. Preferably, it is more preferably 30% or less.

The graphene sheet composition preferably has a high content of graphene sheets with a small number of layers.

The content of the graphene sheet of seven or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, and 2% or less. Is more preferable and 0% is particularly preferable. In the graphene sheet composition, if the content of seven or more layers of graphene sheets exceeds 15%, the features of graphene are not utilized.

In addition, the graphene sheet composition manufacturing apparatus 100 is merely an example, and a graphene sheet composition may be manufactured using a graphene sheet composition manufacturing apparatus having another configuration.

(First embodiment of lithium ion secondary battery)
The negative electrode active material includes a graphene sheet composition, and the graphene sheet composition includes graphene as a main component in a range of 30% to less than 100%. The graphene sheet composition is 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%, and 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 of low-definition and highly crystalline graphene cannot be obtained, and the discharge capacity and rapid charge / discharge characteristics of the lithium ion secondary battery are deteriorated. .

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

The carbon material is not particularly limited, but graphite materials such as artificial graphite, pyrolytic graphite, expanded graphite, natural graphite, scaly graphite, scaly graphite, graphitizable carbon, non-graphitizable carbon, glassy carbon, Examples thereof include carbonaceous materials with undeveloped crystals such as amorphous carbon and low-temperature calcined charcoal.

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, and preferably 50% by mass or less.

As the graphene sheet composition, for example, a material containing 30% or more of graphene as a main component, and further including 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets is arbitrarily selected. be able to.

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 and 50% or less. Preferably, it is more preferably 30% or less.

The graphene sheet composition preferably has a high content of graphene sheets with a small number of layers.

The content of the graphene sheet of seven or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, and 2% or less. Is more preferable and 0% is particularly preferable. When the content of the graphene sheet of 7 layers or more in the graphene sheet composition exceeds 15%, the high occlusion / release properties with respect to lithium ions possessed by the graphene in the negative electrode active material are reduced, and the lithium ion secondary battery The discharge capacity and rapid charge / discharge characteristics may be reduced.

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

Graphene and graphene sheet (graphene sheet composition) manufactured by the above-described method for manufacturing a graphene sheet composition are manufactured without going through graphite oxide, so that there are few defects such as pentagonal and heptagonal cells. And has excellent electrochemical stability.

The graphene sheet composition can be preferably used as a negative electrode active material because it contains graphene in a range of 30% to less than 100% and also includes an N-layer graphene sheet.

A lithium ion secondary battery includes, for example, a positive electrode, an electrolytic solution, a separator, and a negative electrode, and is processed into various shapes such as a cylindrical shape, a square shape, a coin shape, and a sheet shape.

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 includes a negative electrode active material, a conductive additive, and a binder.

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

The negative electrode layer can be formed by, for example, applying a negative electrode active material, a conductive additive, a binder, and a paste kneaded with a solvent to a current collector and then drying the paste.

Examples of the solvent include, but are not limited to, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), isopropanol, and water.

Here, when a binder using water as a solvent is used, it is preferable to use a thickener together.

The amount of the solvent added is adjusted so that the viscosity of the paste is easy to apply to the current collector.

The method for applying the paste is not particularly limited.

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

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

Also, the thickness of the negative electrode layer can be adjusted by drying the paste and then performing pressure molding.

Examples of the pressure forming method include a roll pressing method and a press pressing method.

The pressure at the time of pressure molding is usually 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 provide the negative electrode with conductivity and electrode stability (buffering action against volume change in insertion and extraction of lithium ions). Examples thereof include fibers (for example, VGCF (manufactured by Showa Denko)), conductive carbon (for example, Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.), Super C65, Super C45, KS6L (manufactured by TIMCAL)).

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

The binder is not particularly limited, and examples thereof include polyethylene, polypropylene, ethylene propylene terpolymer, butadiene rubber, styrene butadiene rubber, butyl rubber, acrylic rubber, and a polymer compound having high ionic conductivity.

Examples of the polymer compound having a high ionic conductivity include polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphasphazene, polyacrylonitrile and the like.

The mass ratio of the binder to 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 nickel foil, iron foil, stainless steel foil, titanium foil, and aluminum foil.

The positive electrode layer includes, for example, a positive electrode active material, a conductive additive, and a binder.

As the positive electrode active material is not particularly _{limited, LiMn 2 O 4, LiCoO 2} , LiNiO 2, LiFeO 2, V 2 O 5, TiS, MoS , or the like.

The separator is not particularly limited, and examples thereof include non-woven fabrics mainly composed of olefins such as polyethylene and polypropylene, cloths, microporous films, and combinations thereof.

Also, a polymer electrolyte or the like can be used as the separator.

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

The aprotic solvent is not particularly limited, but propylene carbonate, ethylene carbonate, butylene carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide. Dimethylacetamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl butyl carbonate, dipropyl carbonate, Diisopropyl carbonate, dibutyl carbonate, diethyl Glycol, dimethyl ether and the like, may be used in combination.

The electrolyte is not particularly limited as long as it is a lithium salt, but LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, 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 ) (where x and y are natural numbers), LiCl, LiI, and the like. Two or more kinds may be used in combination.

A small amount of a substance that decomposes during the first charge may be added to the electrolytic solution.

The substance that decomposes during the initial charge is not particularly limited, and examples include vinylene carbonate, biphenyl, propane sultone, and the like.

The content of the substance that decomposes during the 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 includes a sheet-like negative electrode 2, a sheet-like positive electrode 3, a separator 4 disposed between the negative electrode 2 and the positive electrode 3, a negative electrode 2, and a positive electrode 3. And an electrolytic solution impregnated in the separator 4, a cylindrical battery container 5, and a sealing member 6 that seals the battery container 5. The lithium ion secondary battery 1 is accommodated in a battery container 5 in a state where a negative electrode 2, a positive electrode 3, and a separator 4 are overlapped and wound.

A battery constructed by connecting a plurality of lithium ion secondary batteries 1 is particularly called an assembled battery. The assembled battery is configured by connecting two or more lithium ion secondary batteries in series and / or in parallel. Thereby, the capacity | capacitance and voltage of an assembled battery can be adjusted freely.

Lithium-ion rechargeable batteries are power supplies for buildings, houses, tents, etc., fluorescent lamps, LEDs, organic EL, street lights, indoor lighting, traffic lights, etc., machinery, agricultural equipment, beauty equipment, portable tools, Power supplies for vehicles, power supplies for mobile information terminals such as home appliances, electronic devices, mobile phones, power supplies for sanitary equipment such as bath and toilet products, furniture, toys, decorations, bulletin boards, cooler boxes, outdoor generators, etc. It is used by being mounted on various articles such as outdoor power supplies, teaching materials, artificial flowers, objects, power supplies for cardiac pacemakers, and power supplies for heating and cooling devices equipped with Peltier elements.

(Second embodiment of a lithium ion secondary battery)
The second embodiment of the lithium ion secondary battery has the same configuration as that of the first embodiment of the lithium ion secondary battery except for the negative electrode active material.

The negative electrode active material includes a graphene sheet composition and metal particles capable of inserting and extracting lithium ions, and the graphene sheet composition includes graphene as a main component in a range of 30% to less than 100%. The graphene sheet composition is 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%, and 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 capacity due to low defect and highly crystalline graphene and the volume accompanying expansion and contraction in the charge and discharge process in the insertion and extraction of lithium ions by metal particles The stress relaxation action to change cannot be obtained, and the discharge capacity and rapid charge / discharge characteristics of the lithium ion secondary battery are deteriorated. That is, the large volume change of the metal particles capable of occluding and desorbing lithium ions is reduced by the stress relaxation effect of inclusion (or sandwich) with multiple graphenes, and the large negative electrode activity generated during the charge / discharge cycle process is reduced. This reduces the effect of absorbing internal stress, strain, etc. due to the volume expansion / contraction of the substance.

In order to obtain a desired charge / discharge capacity and battery characteristics, the negative electrode active material can be used by adjusting the graphene sheet composition and metal particles capable of occluding and desorbing lithium ions with any content. .

In addition, the negative electrode active material may further contain a carbon material as necessary in order to obtain a desired charge / discharge capacity and battery characteristics.

The carbon material is not particularly limited, but graphite materials such as artificial graphite, pyrolytic graphite, expanded graphite, natural graphite, scaly graphite, scaly graphite, graphitizable carbon, non-graphitizable carbon, glassy carbon, Examples thereof include a carbonaceous material with an undeveloped crystal such as amorphous carbon (carbon) and low-temperature calcined charcoal.

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 1 to 70% by mass, preferably 10 to 70% by mass, and more preferably 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, and preferably 50% by mass or less.

As the graphene sheet composition, for example, a material containing 30% or more of graphene as a main component, and further including 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets is arbitrarily selected. be able to.

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 less than 70% and less than 50%. Preferably, it is less than 30%.

The graphene sheet composition preferably has a high content of graphene sheets with a small number of layers.

The content of the graphene sheet of seven or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, and 2% or less. Is more preferable and 0% is particularly preferable. When the content of the graphene sheet of 7 layers or more in the graphene sheet composition exceeds 15%, the high occlusion / release properties with respect to lithium ions possessed by the graphene in the negative electrode active material are reduced, and the lithium ion secondary battery The discharge capacity and rapid charge / discharge characteristics may be reduced.

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

Since the graphene and the graphene sheet manufactured by the above-described method for manufacturing a graphene sheet composition are manufactured without going through graphite oxide, they have a structure with few defects such as pentagonal and heptagonal cells, and electrochemical Excellent in mechanical stability.

The graphene sheet composition can be preferably used as a negative electrode active material because it contains graphene in a range of 30% to less than 100% and also includes an N-layer graphene sheet.

The material constituting the metal particles capable of occlusion and desorption of lithium ions is not particularly limited as long as it is a metal capable of occlusion and desorption of lithium ions, but silicon (Si), aluminum (Al), tin (Sn), germanium (Ge), antimony (Sb), bismuth (Bi), zinc (Zn), and the like may be used, and two or more of them may be used in combination. Among these, silicon (Si), aluminum (Al), and tin (Sn) are preferable.

The metal particles capable of occluding and desorbing lithium ions are particles containing metal elements and include alloys. The metal particles capable of inserting and extracting lithium ions may partially contain oxides, nitrides, carbides, phosphides, and sulfides. Furthermore, the metal particles capable of inserting and extracting lithium ions include solid solutions containing metal elements, eutectic mixtures, and intermetallic compounds.

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

In the present specification and claims, the particle size of the metal particles means the primary particle size.

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

The mass ratio of the metal particles capable of occluding and desorbing lithium ions with respect to the graphene sheet composition is usually from 0.01 to 1, and preferably from 0.1 to 1. If the mass ratio of the metal particles capable of occluding and desorbing lithium ions with respect 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 the ratio exceeds 1. In addition, the graphene sheet composition may not be able to relax the volume change accompanying the large expansion / contraction and the strain and stress in the negative electrode layer in the insertion and extraction of lithium ions.

(Conductive aid)
A conductive support agent contains a graphene sheet composition, and a graphene sheet composition contains graphene as a main component in 30% or more and less than 100% of range. The graphene sheet composition is 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%, and more preferably 70% or more and less than 100%. When the content of graphene in the graphene sheet composition is less than 30%, conductivity due to low defect and high crystalline graphene cannot be obtained, and the discharge capacity and rapid charge / discharge characteristics of the lithium ion secondary battery are deteriorated. .

The conductive additive may further contain a known carbon material such as carbon black, if necessary, in order to obtain a desired charge / discharge capacity and battery characteristics.

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

Moreover, when a conductive support agent further contains other carbon materials other than a graphene sheet composition, content of the carbon material in a conductive support agent is 70 mass% or less normally, and may be 50 mass% or less. Preferably, it is 30% by mass or less.

As the graphene sheet composition, for example, a material containing 30% or more of graphene as a main component, and further including 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 or more layers of graphene sheets is arbitrarily selected. be able to.

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 and 50% or less. Preferably, it is more preferably 30% or less.

The graphene sheet composition preferably has a high content of graphene sheets with a small number of layers.

The content of the graphene sheet of seven or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, and 2% or less. Is more preferable and 0% is particularly preferable. When the content of the graphene sheet of seven or more layers in the graphene sheet composition exceeds 15%, the conductivity of the graphene in the conductive auxiliary agent decreases, and when applied to the negative electrode of a lithium ion secondary battery, The discharge capacity and rapid charge / discharge characteristics may deteriorate.

Since the graphene sheet composition contains graphene in a range of 30% or more and less than 100% and also includes an N-layer graphene sheet, it can be preferably used as a conductive aid.

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

When applying the conductive assistant to the negative electrode of a lithium ion secondary battery, the mass ratio of the conductive assistant to the negative electrode active material is usually 0.1 to 1.

(Resin composite material)
The resin composite material includes a graphene sheet composition and a synthetic resin, and the graphene sheet composition includes graphene as a main component in a range of 30% to less than 100%. The graphene sheet composition is 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%, and more preferably 70% or more and less than 100%. When the content of graphene in the graphene sheet composition is less than 30%, the contribution of the high conductivity of the low defect and highly crystalline graphene 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 0.1 to 95% by mass, preferably 1 to 70% by mass, and more preferably 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 conductivity, thermal conductivity, and the like of the resin composite material are lowered, and the practical use range is extremely limited.

As the graphene sheet composition, a material containing graphene as a main component in a range of 30% or more and less than 100% is arbitrarily selected from 2 to 3 layers of graphene sheets, 4 to 6 layers of graphene sheets, and 7 layers or more of graphene sheets Can be selected.

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 and 50% or less. Preferably, it is more preferably 30% or less.

The graphene sheet composition preferably has a high content of graphene sheets with a small number of layers.

The content of the graphene sheet of seven or more layers in the graphene sheet composition is usually 15% or less, preferably 10% or less, more preferably 5% or less, and 2% or less. Is more preferable and 0% is particularly preferable. When the content of seven or more graphene sheets in the graphene sheet composition 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 the graphene and the graphene sheet manufactured by the method for manufacturing a graphene sheet composition described above are manufactured without going through graphite oxide, they have a structure with few defects such as pentagonal and heptagonal cells, and have high conductivity. Sex can be imparted.

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

The synthetic resin is not particularly limited, but polyolefin such as polyethylene, polypropylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, etc. Resins, graft-modified polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers graft-modified with unsaturated dicarboxylic acid or anhydrides thereof, styrene resins such as polystyrene, AS resin, and ABS resin, polyvinyl chloride , Vinyl chloride resins such as polyvinylidene chloride, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyether resins such as polyacetal and polyphenylene ether, polymethyl methacrylate, polymer Examples include acrylic resins such as til acrylate, fluorine resins such as polyvinylidene fluoride, and thermoplastic resins such as polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, and polyether ether ketone. Good. Among these, polyacetal resin, polyphenylene ether, polycarbonate, and ABS resin are preferable.

The resin composite material further contains additives such as a softening agent (plasticizer), a foaming agent, a crosslinking agent, a colorant, an antioxidant, a dispersant, a flame retardant, an ultraviolet ray preventing agent, and a lubricant as necessary. Also good.

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

Further, the resin composite material may be manufactured by forming a masterbatch including the graphene sheet composition and the synthetic resin and then molding using a mixer.

The mixer is not particularly limited, and examples thereof include a single screw extruder, a twin screw extruder, a Banbury mixer, a Henschel mixer, a plast mill, and a roll molding machine.

Resin composite materials can be applied to conductive materials for electromagnetic shielding, conductive connection materials, housing materials such as various electronic components, various industrial products, and the like.

In addition, the resin composite material can be used for various industrial products that require anisotropy of electrical conductivity and thermal conductivity. For example, by mixing (kneading) a synthetic resin such as a binder resin, pressure-sensitive adhesive or adhesive and a graphene sheet composition, an anisotropic conductive sheet, an anisotropic conductive film, an anisotropic conductive paint, an anisotropic conductive property It can be used as an anisotropic conductive material such as an adhesive, an anisotropic conductive pressure-sensitive adhesive, an anisotropic conductive paste, and an anisotropic conductive ink. Anisotropic conductive materials are generally applied to electronic devices such as personal computers, personal digital assistance, mobile phones, liquid crystal televisions, etc., and electrically connect adjacent substrates, or small electronic components such as semiconductor elements. Is electrically bonded to the substrate. Further, the anisotropic conductive material is applied to anisotropic conductors and heat conductors by being sandwiched between opposing substrates and electrode terminals and crimped.

The method for producing the anisotropic conductive material is not particularly limited, but the graphene sheet composition is added at an arbitrary concentration in the insulating binder resin or in the insulating adhesive / adhesive, and mixed uniformly. Examples of the method include dispersion.

As an example, a method for producing a conductive anisotropic sheet and a conductive anisotropic film will be described. Insulating binder resin and insulating adhesive / adhesive are dissolved in heat-melting or organic solvent to give fluidity, and then the graphene sheet composition is added and mixed uniformly. In some cases, the graphene sheet composition is oriented as necessary. Thereafter, the binder resin, the pressure-sensitive adhesive / adhesive is cured. Moreover, an anisotropic conductive sheet can be manufactured by the extrusion method, and an anisotropic conductive film can be manufactured by the calendar method and the casting method.

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

(Example 1)
A graphene sheet composition was manufactured under the following conditions using a continuous flow graphene sheet composition manufacturing apparatus (see FIG. 1).

First, a graphite dispersion in which graphite having a particle size of 20 μm or less (manufactured by Aldrich) is dispersed in ethanol for supercritical fluid at a concentration of 1 mg / ml is prepared in a storage container 115, and 10 ml of graphite dispersion is prepared by a pump 130. It was supplied to the supercritical processor 155 at a flow rate of / min. The supercritical condition in the supercritical processor 155 is 420 ° C. and 12 MPa, and the residence time of the dispersion liquid in the supercritical processor 155 (the time from introduction from the inlet to discharge from the outlet) is about 1.3. The liquid flowed as minutes. Ultrasonic vibration was applied to the supercritical processor 155 from the outside. 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 again supplied to the supercritical processor 155 under the same conditions using the pump 130. Continued to supply. At this time, a predetermined amount of the discharged ethanol dispersion liquid was stored in the storage tank 115, and the supply of the solvent to the supercritical processor 155 was discontinuously repeated. The number of repetitions of supplying the solvent to the supercritical processor 155 was three. At this time, the time required for the supercritical processing was 4 minutes.

The dispersion liquid subjected to the supercritical treatment was sent to the container 185, and the solvent was distilled off, followed by vacuum drying to obtain a powdery graphene sheet composition. In addition, before distilling off the solvent, the exfoliated graphite in which the number of laminated layers of raw material graphite and graphene exceeded 20 layers was separated and removed by centrifuging under predetermined conditions. In the graphene sheet composition, graphene is not detected, the content of the graphene sheet of 2 to 3 layers is 15%, the content of the graphene sheet of 4 to 6 layers is 60%, and the graphene of 7 layers or more The sheet content was 25%.

(Example 2)
A powder graphene sheet composition was obtained in the same manner as in Example 1 except that the number of supercritical treatments was changed to 6. At this time, the time required for the supercritical processing was 8 minutes. In the graphene sheet composition, no graphene is detected, the content of the graphene sheet of 2 to 3 layers is 45%, the content of the graphene sheet of 4 to 6 layers is 35%, and the graphene of 7 layers or more The sheet content was 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 12. At this time, the time required for the supercritical processing was 16 minutes. The graphene sheet composition has a graphene content of 35%, a 2 to 3 layer graphene sheet content of 30%, a 4 to 6 layer graphene sheet content of 21%, and a 7 layer The content of the above graphene sheet was 14%.

Using an SPM (scanning probe microscope) Agilent 5500 (manufactured by Toyo Technica Co., Ltd.), when the thickness [nm] at any 30 locations of the graphene sheet composition was measured, the content of graphene was 2 to 20 layers. It was found that the content of the graphene sheet was larger than that of the graphene sheet.

FIG. 4 shows a TEM photograph of the graphene sheet composition. From FIG. 4, the end face of graphene was 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 processing was 62 minutes. In the graphene sheet composition, the content of graphene was 90%, the content of 2 to 3 layers of graphene sheets was 10%, and 4 or more layers of graphene sheets were not detected.

Using SPM (scanning probe microscope) Agilent 5500 (manufactured by Toyo Technica Co., Ltd.), when the thickness [nm] of any 30 locations of the graphene sheet composition was measured, the graphene content was two graphene sheets each It was found that the content was higher than that of the three-layer graphene sheet.

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

FIG. 5 shows the evaluation results of the composition of the graphene sheet compositions of Examples 1 to 4.

(Particle size distribution of graphene sheet composition)
When the particle size distribution of the graphene sheet compositions obtained in Examples 1 to 4 was measured using a laser diffraction apparatus Shimadzu SalD-700 (manufactured by Shimadzu Corporation), the median diameter (D50) was several tens nm to 200 nm. A range of nanoparticles was observed.

(Preparation of lithium ion secondary battery 1-1)
Using the graphene sheet composition of Example 3 as the 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 a binder, and 10 parts of carbon black (commercial product) as a conductive assistant were weighed, and an appropriate amount of N-methyl- 2-Pyrrolidone (NMP) was added and mixed by stirring to prepare a negative electrode paste.

Next, a negative electrode paste was applied on a copper foil having a thickness of 20 μm by a doctor blade method to a thickness of about 100 μm, and then vacuum-dried at 80 ° C. overnight to obtain a negative electrode layer. The negative electrode layer was cut out into a cylindrical shape having a diameter of 15 mm by 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 polypropylene porous film (commercial product) having a thickness of 25 μm was prepared as a separator. In addition, LiPF ₆ as an electrolyte was dissolved at a concentration of 1 mol / dm ³ in an aprotic solvent in which 30% by volume of ethylene carbonate and 70% by volume of methyl ethyl carbonate were mixed to prepare an electrolytic solution.

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

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

(Production of lithium ion secondary battery 1-3)
Graphite (manufactured by Aldrich) having a particle size of 20 μm or less was oxidized with concentrated sulfuric acid, sodium nitrate and potassium permanganate according to the known Hummers method (US Pat. No. 2,798,878, July 9, 1957). Thereafter, the obtained graphite oxide was heat-treated and reduced in a non-oxidizing atmosphere at about 400 ° C. to obtain a reduced form of powdered graphite oxide.

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

Next, a charge / discharge test was conducted at 25 ° C. using the lithium ion secondary batteries 1-1 to 1-3.

(Charge / discharge test)
The charge / discharge test was performed by charging the battery potential from the rest potential to 20 mV at a constant current, and then discharging to 1.5 V at a constant current.

The current value was set such that the nominal capacity value was 372 mAh / g and the C rate was 0.1 C during charging and discharging. However, 0.1 C is a current value at which charging and discharging are completed in 10 hours after a cell having a nominal capacity value is charged with a constant current and then discharged. The discharge capacity (initial discharge capacity) of the first cycle of the battery was measured. In addition, C rate generally represents the electric current value of charging / discharging of a battery, and is represented by C rate = electric current value (A) / capacity (Ah). When a battery having a capacity of 1 Ah is charged and discharged at 1 A, it is expressed as 10 C when charged and discharged at 1 C and 10 A.

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

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

　表１から、リチウムイオン二次電池１－１は、初回放電容量及び放電容量保持率が優れることがわかる。

From Table 1, it can be seen that the lithium ion secondary battery 1-1 is excellent in initial 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 rate are reduced.

In addition, since the lithium ion secondary battery 1-3 uses a reduced form of graphite oxide as the negative electrode active material, the initial discharge capacity and the discharge capacity retention rate are lowered. Here, the reduced form of graphite oxide has some oxygen functional groups remaining even after heat reduction, and defects other than the hexahedral structure due to elimination of oxygen functional groups (hydroxyl groups, epoxy groups, carboxy groups, etc.). Therefore, the potential flat region in the charge / discharge curve was poor.

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

First, 72 parts of a graphene sheet composition, 8 parts of silicon particles, 10 parts of polyvinylidene fluoride (commercial product) as a binder, and 10 parts of carbon black (commercial product) as a conductive additive are weighed, and an appropriate amount is obtained. N-methyl-2-pyrrolidone (NMP) was added and mixed by stirring to prepare an electrode paste for negative electrode.

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

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

(Preparation of lithium ion secondary battery 2-3)
Graphite (manufactured by Aldrich) having a particle size of 20 μm or less was oxidized with concentrated sulfuric acid, sodium nitrate and potassium permanganate according to the known Hummers method (US Pat. No. 2,798,878, July 9, 1957). Thereafter, the obtained graphite oxide was heat-treated and reduced in a non-oxidizing atmosphere at about 400 ° C. to obtain a reduced form of powdered graphite oxide.

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

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

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

　表２から、リチウムイオン二次電池２－１は、初回放電容量及び放電容量保持率が優れることがわかる。

From Table 2, it can be seen that the lithium ion secondary battery 2-1 is excellent in initial discharge capacity and discharge capacity retention.

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

In addition, since the lithium ion secondary battery 2-3 uses a graphite oxide reductant and silicon particles as the negative electrode active material, the initial discharge capacity and the discharge capacity retention rate are lowered. Here, the reduced form of graphite oxide has some oxygen functional groups remaining even after heat reduction, and defects other than the hexahedral structure due to elimination of oxygen functional groups (hydroxyl groups, epoxy groups, carboxy groups, etc.). Therefore, the potential flat region in the charge / discharge curve was poor.

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

First, 72 parts of graphite (manufactured by Aldrich) having a particle size of 20 μm or less as a negative electrode active material and 8 parts of silicon particles, 10 parts of polyvinylidene fluoride (commercial product) as a binder, and 10 parts of a graphene sheet composition are weighed. Then, an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added thereto and mixed by stirring to prepare an electrode paste for 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 negative electrode was used.

Next, a charge / discharge test was performed at 25 ° C. using the lithium ion secondary battery 3-1 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 that of the lithium ion secondary battery 2-2, and the discharge capacity retention rate is improved. It improved by about 20% at 5% and 5C.

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

First, 10% by mass of a graphene sheet composition is blended with polyacetal resin Duracon M90 (manufactured by Polyplastics Co., Ltd.) as a synthetic resin, dry blended using a planetary stirrer, and then melted using an extruder. The plate 1 having a size of 100 mm × 100 mm × 2 mm was injection molded with an injection molding machine. When cut out from the flat plate 1 to a width of 1 mm and measured by the four-end needle method, it was 1.2 × 10 ⁴ Ω.

(Preparation of flat plate 2)
A flat plate 2 was produced in the same manner as the flat plate 1 except that graphite (manufactured by Aldrich) having a particle size of 20 μm or less was used instead of the graphene sheet composition of Example 3. When cut out from the flat plate 2 to a width of 1 mm and measured by the four-end needle method, it was 5.0 × 10 ⁶ Ω.

(Preparation of flat plate 3)
Graphite (manufactured by Aldrich) having a particle size of 20 μm or less was oxidized with concentrated sulfuric acid, sodium nitrate and potassium permanganate according to the known Hummers method (US Pat. No. 2,798,878, July 9, 1957). Thereafter, the obtained graphite oxide was heat-treated and reduced in a non-oxidizing atmosphere at about 400 ° C. to obtain a reduced form of powdered graphite oxide.

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

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

　表３から、平板１の導電性が優れることがわかる。

From Table 3, it can be seen that the conductivity of the flat plate 1 is excellent.

On the other hand, the conductivity of the flat plate 2 is reduced because graphite is used as the carbon material filler.

Moreover, since the flat plate 3 uses a reduced form of graphite oxide as a carbon material filler, the conductivity decreases. Here, the reduced form of graphite oxide has some oxygen functional groups remaining even after heat reduction, and defects other than the hexahedral structure due to elimination of oxygen functional groups (hydroxyl groups, epoxy groups, carboxy groups, etc.). Therefore, the potential flatness region in the charge / discharge curve was poor.

This international application claims priority based on Japanese Patent Applications 2012-265833, 2012-265834, 2012-265835, 2012-265836 filed on Dec. 4, 2012. The entire contents of -265833, 2012-265834, 2012-265835, 2012-265836 are incorporated herein by reference.

DESCRIPTION OF SYMBOLS 100 Graphene sheet composition manufacturing apparatus 110 Raw material part 115 Storage container 120 Solvent in which graphite is dispersed 125 Pipe 130 Pump 150 Supercritical processing part 155 Supercritical processor 160 Vibrating means 165 Pipe 168 Cooling tank 170 Switching valve 172 Pipe 174 Piping 180 Recovery unit 185 Container

Claims (20)

Containing 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 graphene sheet composition according to claim 1, comprising 7 or more layers of graphene sheets at 15% or less. A negative electrode active material for a lithium ion secondary battery, comprising the graphene sheet composition according to claim 1. A negative electrode for a lithium ion secondary battery comprising the negative electrode active material for a lithium ion secondary battery according to claim 3. A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to claim 4. An assembled battery comprising the lithium ion secondary battery according to claim 5. A negative electrode active material for a lithium ion secondary battery comprising the graphene sheet composition according to claim 1 and metal particles capable of occluding and desorbing lithium ions. The negative electrode active material for a lithium ion secondary battery according to claim 7, wherein the metal particles include one or more selected from the group consisting of aluminum, silicon, and tin. A negative electrode for a lithium ion secondary battery comprising the negative electrode active material for a lithium ion secondary battery according to claim 7. A lithium ion secondary battery comprising the negative electrode for a lithium ion secondary battery according to claim 9. An assembled battery comprising the lithium ion secondary battery according to claim 10. A conductive additive comprising the graphene sheet composition according to claim 1. An electrode comprising the conductive additive according to claim 12. A battery comprising the electrode according to claim 13. A resin composite material comprising the graphene sheet composition according to claim 1 and a synthetic resin. (A) supplying a solvent containing graphite to a supercritical processing plant;
(B) bringing the solvent supplied to the supercritical processing plant into a supercritical state;
(C) having a step of returning the solvent in the supercritical state to a non-supercritical state;
In the steps (a) to (c), the solvent is flowed in a continuous flow system,
A method for producing a graphene sheet composition, wherein the steps (a) to (c) are repeated a plurality of times continuously and / or discontinuously. The method of producing a graphene sheet composition according to claim 16, wherein the step (b) and / or (c) is performed in a state where vibration is applied. The method for producing a graphene sheet composition according to claim 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. (A) means for supplying a solvent containing graphite to a supercritical processing station;
(B) means for bringing the solvent supplied to the supercritical processing plant into a supercritical state;
(C) a means for returning the supercritical solvent to a non-supercritical state;
The apparatus (a) to (c) is an apparatus for producing a graphene sheet composition, wherein the solvent is flowed in a continuous flow system. The apparatus for producing a graphene sheet composition according to claim 19, wherein the means (b) and / or (c) includes means for applying vibration.

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