# US 10,122,047 B2 · Nonaqueous electrolyte secondary battery

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- Number: US 10,122,047 B2
- Document ID: US10122047B2
- Status: Granted
- Kind: B2
- Application number: 14/661,249
- Filed: 2015-03-18
- Published: 2015-10-01
- Granted: 2018-11-06
- Earliest claimed: 2014-03-26
- Assignees: Toyota Jidosha Kabushiki Kaisha
- Applicants: Toyota Jidosha Kabushiki Kaisha
- Inventors: Yutaka Oyama
- Web page: https://patentgrep.com/patent/US10122047B2

## CPC

- H01M 10/0568: characterised by the solutes
- H01M 4/583: Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M 10/052: Li-accumulators
- H01M 2010/4292: {Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode}
- H01M 2300/0025: Organic electrolyte
- H01M 2300/0045: Room temperature molten salts comprising at least one organic ion
- Y02E 60/10: Energy storage using batteries
- Y02T 10/70: Energy storage systems for electromobility, e.g. batteries
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A nonaqueous electrolyte secondary battery proposed herein is configured such that a positive-electrode active material layer includes graphite particles and a gas generant. Further, an electrolyte solution includes an α solute. Here, a relationship between an upper limit electric potential X of a positive electrode in a predetermined normal use area, an electric potential Y at which an amount of the α solute in the electrolyte solution begins to decrease due to the graphite particles, and an electric potential Z at which the gas generant begins to generate gas is X<Y<Z.

## Claims

### Claim 1

A nonaqueous electrolyte secondary battery comprising:
a battery outer case;
an electrode body accommodated in the battery outer case, where the electrode body includes a positive current collector and a positive-electrode active material layer held by the positive current collector, the positive-electrode active material layer includes graphite particles and a gas generant in a solid content, and the gas generant is cyclohexylbenzene; and
an electrolyte solution accommodated in the battery outer case, where the electrolyte solution includes an α solute, and the α solute is selected from the group consisting of imidazolium salt, pyridinium salt, and pyrrolidinium salt,
wherein the nonaqueous electrolyte secondary is configured such that an electrical potentials relationship of X<Y<Z is satisfied when the nonaqueous electrolyte secondary is in use, where X is an upper limit electric potential of a positive electrode in a predetermined normal use area, Y is an electric potential at which an amount of the α solute in the electrolyte solution begins to decrease due to the graphite particles, Z is an electric potential at which the gas generant begins to generate gas, the electric potentials are based on an equilibrium potential (vs. Li/Li+) of metallic lithium, and X is from 3.9 to 4.3 V;
an amount of the gas generant in the nonaqueous electrolyte secondary battery is equal to or larger than 3.0 wt % and less than 7.0 wt % relative to the electrolyte solution; and
the positive-electrode active material layer includes at least one third of the gas generant included in the nonaqueous electrolyte secondary battery.

### Claim 2 (depends on 1)

The nonaqueous electrolyte secondary battery according to claim 1, wherein
the electric potential Y is an electric potential within a range from an electric potential lower than the electric potential Z by 0.05 V to an electric potential lower than the electric potential Z by 0.35 V.

### Claim 3 (depends on 1)

The nonaqueous electrolyte secondary battery according to claim 1, wherein
a mass ratio of the graphite particles included in the positive-electrode active material layer is larger than a mass ratio of the gas generant included in the positive-electrode active material layer.

### Claim 4 (depends on 1)

The nonaqueous electrolyte secondary battery according to claim 1, wherein
the graphite particles are flake graphite.

### Claim 5 (depends on 1)

The nonaqueous electrolyte secondary battery according to claim 1, wherein
the α solute is an ionic liquid including a cation having a planar structure insertable between layers of the graphite particles.

### Claim 6 (depends on 1)

The nonaqueous electrolyte secondary battery according to claim 1, wherein
an additive amount of the α solute in the electrolyte solution is less than 5 mol/L.

### Claim 7

A nonaqueous electrolyte secondary battery comprising:
a battery outer case;
an electrode body accommodated in the battery outer case, where the electrode body includes a positive current collector and a positive-electrode active material layer held by the positive current collector, the positive-electrode active material layer includes graphite particles and a gas generant in a solid content, and the gas generant is cyclohexylbenzene; and
an electrolyte solution accommodated in the battery outer case, where the electrolyte solution includes an α solute, and the α solute is selected from the group consisting of imidazolium salt, pyridinium salt, and pyrrolidinium salt,
wherein the nonaqueous electrolyte secondary is configured such that an electrical potentials relationship of X<Y<Z is satisfied when the nonaqueous electrolyte secondary is in use, where X is an upper limit electric potential of a positive electrode in a predetermined normal use area, Y is an electric potential at which an amount of the α solute in the electrolyte solution begins to decrease due to the graphite particles, Z is an electric potential at which the gas generant begins to generate gas, the electric potentials are based on an equilibrium potential (vs. Li/Li+) of metallic lithium, and X is 3.9 to 4.3 V; and
an additive amount of the α solute in the electrolyte solution is less than 5 mol/L.

### Claim 8 (depends on 7)

The nonaqueous electrolyte secondary battery according to claim 7, wherein
the electric potential Y is an electric potential within a range from an electric potential lower than the electric potential Z by 0.05 V to an electric potential lower than the electric potential Z by 0.35 V.

### Claim 9 (depends on 7)

The nonaqueous electrolyte secondary battery according to claim 7, wherein
a mass ratio of the graphite particles included in the positive-electrode active material layer is larger than a mass ratio of the gas generant included in the positive-electrode active material layer.

### Claim 10 (depends on 7)

The nonaqueous electrolyte secondary battery according to claim 7, wherein
the graphite particles are flake graphite.

### Claim 11 (depends on 7)

The nonaqueous electrolyte secondary battery according to claim 7, wherein
the α solute is an ionic liquid including a cation having a planar structure insertable between layers of the graphite particles.

### Claim 12 (depends on 7)

The nonaqueous electrolyte secondary battery according to claim 7, wherein
an amount of the gas generant in the nonaqueous electrolyte secondary battery is equal to or larger than 3.0 wt % and less than 7.0 wt % relative to the electrolyte solution.

### Claim 13 (depends on 7)

The nonaqueous electrolyte secondary battery according to claim 7, wherein
the positive-electrode active material layer includes at least one third of the gas generant included in the nonaqueous electrolyte secondary battery.