# US 9,520,595 B2 · Negative electrode for lithium-ion secondary cell and method for manufacturing same

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- Number: US 9,520,595 B2
- Document ID: US9520595B2
- Status: Granted
- Kind: B2
- Application number: 14/439,063
- Filed: 2013-10-23
- Published: 2015-10-29
- Granted: 2016-12-13
- Earliest claimed: 2012-10-29
- Assignees: Sango Co., Ltd.; City of Nagoya
- Applicants: SANGO Co., Ltd.; City of Nagoya
- Inventors: Kouichi Izuhara; Makoto Daifuku; Yasushi Miyata
- Web page: https://patentgrep.com/patent/US9520595B2

## CPC

- H01M 4/587: for inserting or intercalating light metals
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01B 32/182: Graphene
- H01M 4/0428: {Chemical vapour deposition}
- H01M 4/133: Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M 4/1393: of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M 4/661: {Metal or alloys, e.g. alloy coatings (H01M4/669 take precedence)}
- H01M 10/0525: Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
- Y02E 60/10: Energy storage using batteries
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- 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

A negative electrode for a lithium-ion secondary cell is configured in a novel manner, having a charge-discharge capacity, as determined per unit weight of the carbon used in the electrode, that is markedly higher than the theoretical capacity of graphite, and having a surface that is stabilized against repeated charging and discharging. A negative electrode for a lithium-ion secondary cell in which a carbon layer obtained by building up and growing a graphene sheet is formed on the surface of a substrate comprising an iron-based metal, the carbon layer being formed in a diagonal direction in relation to the substrate, and the carbon layer being used as the surface of the negative electrode. As measured using an argon laser having a wavelength of 532 nm, the Raman spectrum of the graphite that constitutes the carbon nanochip layer has a g/d ratio of 0.30-0.80.

## Claims

### Claim 1

A negative electrode for a lithium-ion secondary cell, the negative electrode comprising: a substrate formed of an iron-based metal; and graphene sheets grown on the substrate to stand in directions oblique to a surface of the substrate to form a carbon layer, wherein the carbon layer is used as a negative electrode surface.

### Claim 2 (depends on 1)

The negative electrode for a lithium-ion secondary cell according to claim 1, wherein the carbon layer consists of a carbon nanochips layer formed from graphene sheets grown slantingly from the surface of the substrate in various directions.

### Claim 3 (depends on 2)

The negative electrode for a lithium-ion secondary cell according to claim 2, wherein the coverage of the substrate surface by the carbon nanochips layer is 100%.

### Claim 4 (depends on 1)

The negative electrode for a lithium-ion secondary cell according to claim 1, wherein the iron-based metal includes pure iron, carbon steel, stainless steel, or an iron alloy.

### Claim 5 (depends on 1)

The negative electrode for a lithium-ion secondary cell according to claim 1, wherein in a Raman spectrum of graphite forming the carbon nanochips layer measured using an argon laser having a wavelength of 532 nm, g/d is in a range of 0.30 to 0.80, wherein g represents the peak intensity of a g band at approximately 1,600 cm−1 caused by in-plane hexagonal lattice vibration of carbon atoms, and d represents the peak intensity of a d band at approximately 1,360 cm−1 which indicates a graphite defect.

### Claim 6 (depends on 1)

The negative electrode for a lithium-ion secondary cell according to claim 1, wherein the carbon nanochips layer is a layer formed by a plasma CVD method using a methane-hydrogen mixed gas as a raw material.

### Claim 7 (depends on 1)

A lithium-ion secondary cell assembled by directly bringing a carbon nanochips layer of the negative electrode for a lithium-ion secondary cell according to claim 1 as a negative electrode surface into contact with an electrolytic solution for a lithium-ion secondary cell.

### Claim 8 (depends on 1)

A method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 1, the method comprising the steps of: setting the substrate in a chamber; and forming on the substrate a carbon nanochips layer composed of graphene sheets independently grown from a negative electrode substrate surface slantingly in irregular directions by a plasma CVD method using a mixed gas containing hydrogen and methane under the conditions in which a flow rate ratio of H2/CH4 is set to 1/5 to 2/1, a process pressure in the chamber is set to 6.7 to 66.7 Pa, substrate temperature is set to 650° C. to 850° C., a DC bias voltage is set to −200 to 0 V, and a growth time is set to 15 minutes to 2 hours.

### Claim 9 (depends on 8)

The method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 8, further comprising, before the plasma CVD method is performed, a step of performing oxygen cleaning of the inside of the chamber by generating plasma in the chamber in the presence of oxygen.

### Claim 10 (depends on 9)

The method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 9, wherein the oxygen cleaning is performed before or after the substrate is set in the chamber.

### Claim 11 (depends on 2)

A lithium-ion secondary cell assembled by directly bringing a carbon nanochips layer of the negative electrode for a lithium-ion secondary cell according to claim 2 as a negative electrode surface into contact with an electrolytic solution for a lithium-ion secondary cell.

### Claim 12 (depends on 3)

A lithium-ion secondary cell assembled by directly bringing a carbon nanochips layer of the negative electrode for a lithium-ion secondary cell according to claim 3 as a negative electrode surface into contact with an electrolytic solution for a lithium-ion secondary cell.

### Claim 13 (depends on 4)

A lithium-ion secondary cell assembled by directly bringing a carbon nanochips layer of the negative electrode for a lithium-ion secondary cell according to claim 4 as a negative electrode surface into contact with an electrolytic solution for a lithium-ion secondary cell.

### Claim 14 (depends on 5)

A lithium-ion secondary cell assembled by directly bringing a carbon nanochips layer of the negative electrode for a lithium-ion secondary cell according to claim 5 as a negative electrode surface into contact with an electrolytic solution for a lithium-ion secondary cell.

### Claim 15 (depends on 6)

A lithium-ion secondary cell assembled by directly bringing a carbon nanochips layer of the negative electrode for a lithium-ion secondary cell according to claim 6 as a negative electrode surface into contact with an electrolytic solution for a lithium-ion secondary cell.

### Claim 16 (depends on 8)

A method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 8, wherein the carbon layer consists of a carbon nanochips layer formed from graphene sheets grown slantingly from the surface of the substrate in various directions.

### Claim 17 (depends on 8)

A method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 8, wherein the coverage of the substrate surface by the carbon nanochips layer is 100%.

### Claim 18 (depends on 8)

A method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 8, wherein the iron-based metal includes pure iron, carbon steel, stainless steel, or an iron alloy.

### Claim 19 (depends on 8)

A method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 8, wherein in a Raman spectrum of graphite forming the carbon nanochips layer measured using an argon laser having a wavelength of 532 nm, g/d is in a range of 0.30 to 0.80, wherein g represents the peak intensity of a g band at approximately 1,600 cm−1 caused by in-plane hexagonal lattice vibration of carbon atoms, and d represents the peak intensity of a d band at approximately 1,360 cm−1 which indicates a graphite defect.

### Claim 20 (depends on 8)

A method for manufacturing the negative electrode for a lithium-ion secondary cell according to claim 8, wherein the carbon nanochips layer is a layer formed by a plasma CVD method using a methane-hydrogen mixed gas as a raw material.