Nonaqueous electrolyte secondary battery

Patent metadata

Field	Value
Publication number	US-10122047-B2
Application number	US-201514661249-A
Country	US
Kind code	B2
Filing date	Mar 18, 2015
Priority date	Mar 26, 2014
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

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.

First claim

What is claimed is:

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.

2. 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.

3. 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.

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

5. 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.

6. 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.

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.

8. 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.

9. 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.

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

11. 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.

12. 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.

13. 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.

Assignees

• Toyota Motor Co Ltd

Inventors

• Oyama Yutaka

Classifications

• H01M2300/0025

  Organic electrolyte · CPC title

• H01M10/0568 Primary

  characterised by the solutes · CPC title

• H01M2010/4292

  Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode · CPC title

• H01M10/052 Primary

  Li-accumulators · CPC title

• H01M4/583

  Carbonaceous material, e.g. graphite-intercalation compounds or CFx · CPC title