# US 12,113,219 B2 · Reduced graphene oxide-graphite composite material, method for producing same, and lithium ion secondary battery using same

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- Number: US 12,113,219 B2
- Document ID: US12113219B2
- Status: Granted
- Kind: B2
- Application number: 17/421,361
- Filed: 2020-01-08
- Published: 2021-12-23
- Granted: 2024-10-08
- Earliest claimed: 2019-01-09
- Assignees: NEC Corporation
- Applicants: NEC Corporation
- Inventors: Katsumi Maeda
- Web page: https://patentgrep.com/patent/US12113219B2

## CPC

- H01M 4/587: for inserting or intercalating light metals
- H01M 10/052: Li-accumulators
- C01B 32/198: Graphene oxide
- C01B 32/20: Graphite
- C01B 32/21: After-treatment
- H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
- H01M 10/0566: Liquid materials
- H01M 2004/027: {Negative electrodes}
- H01M 2220/30: Batteries in portable systems, e.g. mobile phone, laptop
- H01M 2300/0017: Non-aqueous electrolytes
- Y02E 60/10: Energy storage using batteries
- Y02P 20/133: Renewable energy sources, e.g. sunlight
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

An object of the present invention is to provide a reduced graphene oxide-graphite composite material capable of improving battery characteristics such as the charge and discharge efficiency and the capacity retention ratio of a lithium ion secondary battery, and a method for producing the same. The present invention relates to a reduced graphene oxide-graphite composite material in which a reduced graphene oxide and a graphite are formed into a composite, wherein the functional group ratio (C—O/C═O) between C—O bond and C═O bond is 3 to 6 as obtained from a C1s spectrum based on surface analysis measured by X-ray photoelectron spectroscopy (XPS).

## Claims

### Claim 1

A reduced graphene oxide-graphite composite material in which a reduced graphene oxide and a graphite are formed into a composite, wherein a functional group ratio (C—O/C═O) between C—O bond and C═O bond is 3 to 6 as obtained from a C1s spectrum based on surface analysis as measured by X-ray photoelectron spectroscopy (XPS), and a mass ratio of the reduced graphene oxide and the graphite in the reduced graphene oxide-graphite composite is 90:10 to 20:80.

### Claim 2 (depends on 1)

A lithium ion secondary battery comprising a positive electrode comprising a positive electrode active material capable of absorbing and desorbing lithium ions, a negative electrode comprising a negative electrode active material capable of absorbing and desorbing lithium ions, and a nonaqueous electrolyte solution, wherein the negative electrode active material comprises the reduced graphene oxide-graphite composite material according to claim 1.

### Claim 3 (depends on 2)

The lithium ion secondary battery according to claim 2, wherein a content of the reduced graphene oxide-graphite composite material in the negative electrode active material is 10% by mass or more.

### Claim 4 (depends on 1)

The reduced graphene oxide-graphite composite material according to claim 1, wherein a mass ratio of the reduced graphene oxide and the graphite in the reduced graphene oxide-graphite composite material is 80:20 to 40:60.

### Claim 5 (depends on 1)

The reduced graphene oxide-graphite composite material according to claim 1, wherein an XRD spectrum of the reduced graphene oxide-graphite composite material has a peak (1) at a diffraction angle (2θ) of 26° to 27° and a peak (2) at a diffraction angle (2θ) of 25° to 27°, and a ratio of a peak intensity of the peak (2) to a peak intensity of the peak (1) is 0.1 or higher and 0.8 or lower.

### Claim 6 (depends on 2)

The lithium ion secondary battery according to claim 2, wherein a mass ratio of the reduced graphene oxide and the graphite in the reduced graphene oxide-graphite composite material is 80:20 to 40:60.

### Claim 7 (depends on 2)

The lithium ion secondary battery according to claim 2, wherein an XRD spectrum of the reduced graphene oxide-graphite composite material has a peak (1) at a diffraction angle (2θ) of 26° to 27° and a peak (2) at a diffraction angle (2θ) of 25° to 27°, and a ratio of a peak intensity of the peak (2) to a peak intensity of the peak (1) is 0.1 or higher and 0.8 or lower.