Lithium secondary battery, power storage apparatus including lithium secondary battery and method of manufacturing lithium secondary battery

Patent metadata

Field	Value
Publication number	US-2016268608-A1
Application number	US-201514982321-A
Country	US
Kind code	A1
Filing date	Dec 29, 2015
Priority date	Jan 14, 2015
Publication date	Sep 15, 2016
Grant date	—

Abstract

A lithium secondary battery having a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is constituted by a positive electrode mixture layer containing a positive electrode active material, a binder, and a conductive agent being formed on a positive electrode collector, the negative electrode is constituted by a negative electrode mixture layer containing a negative electrode active material, the binder, and the conductive agent being formed on a negative electrode collector, and the conductive agent contained in both of the positive electrode mixture layer and the negative electrode mixture layer is a fibrous conductive agent or a mixture of the fibrous conductive agent and a particulate conductive agent and an aspect ratio of the fibrous conductive agent is 20 or more.

First claim

What is claimed is:

1 . A lithium secondary battery having a positive electrode, a negative electrode, and an electrolyte, wherein
the positive electrode is constituted by a positive electrode mixture layer containing a positive electrode active material, a binder, and a conductive agent being formed on a positive electrode collector, the negative electrode is constituted by a negative electrode mixture layer containing a negative electrode active material, the binder, and the conductive agent being formed on a negative electrode collector, a thickness of the positive electrode mixture layer is 40 μm or less, a percentage of voids of the positive electrode mixture layer is 40% or more and 55% or less, an average particle size of the positive electrode active material is 1 μm or more and 5 μm or less, a volume of the conductive agent in the positive electrode mixture layer is 10% or more and 40% or less of the volume of the binder, and the conductive agent contained in both of the positive electrode mixture layer and the negative electrode mixture layer is a fibrous conductive agent or a mixture of the fibrous conductive agent and a particulate conductive agent and an aspect ratio (radio of a diameter to a length of the fibrous conductive agent) of the fibrous conductive agent is 20 or more.

2 . The lithium secondary battery according to claim 1 , wherein
the percentage of voids of the negative electrode mixture layer is 30% or more and 55% or less, and the average particle size of the negative electrode active material is 1 μm or more and 5 μm or less.

3 . The lithium secondary battery according to claim 1 , wherein
the volume of the fibrous conductive agent contained in the conductive agent is 0.04% or more and 0.5% or less of the volume of the binder in each of the positive electrode mixture layer and the negative electrode mixture layer.

4 . The lithium secondary battery according to claim 1 , wherein
the fibrous conductive agent is at least one of a carbon nanotube and a carbon fiber, and a mass of the fibrous conductive agent is 0.1% or more of the positive electrode active material in the positive electrode mixture layer and 0.1% or more of the negative electrode active material in the negative electrode mixture layer.

5 . The lithium secondary battery according to claim 1 , wherein
the length of the fibrous conductive agent contained in the positive electrode mixture layer is larger than an average radius of the positive electrode active material, and the length of the fibrous conductive agent contained in the negative electrode mixture layer is larger than the average radius of the negative electrode active material.

6 . The lithium secondary battery according to claim 5 , wherein
the length of the fibrous conductive agent contained in the positive electrode mixture layer is smaller than double the average radius of the positive electrode active material, and the length of the fibrous conductive agent contained in the negative electrode mixture layer is smaller than double the average radius of the negative electrode active material.

7 . The lithium secondary battery according to claim 1 , wherein
the fibrous conductive agent couples a plurality of the positive electrode active materials therebetween and a plurality of the negative electrode active materials therebetween by constituting a self-organizing conductive network while being held by the binder in each of the positive electrode mixture layer and the negative electrode mixture layer.

8 . A power storage apparatus including a lithium secondary battery, wherein
the lithium secondary battery is the lithium secondary battery according to claim 1 .

9 . A method of manufacturing the lithium secondary battery according to claim 1 , comprising:
forming a positive electrode mixture layer containing a fibrous conductive agent on a positive electrode collector; forming a negative electrode mixture layer containing the fibrous conductive agent on a negative electrode collector; and holding the positive electrode collector on which the positive electrode mixture layer is formed and the negative electrode collector on which the positive electrode mixture layer is formed at 100° C. or more and 300° C. or less for a predetermined time.

Assignees

• Hitachi Ltd

Inventors

• Nishimura Etsuko
• Okumura Takefumi
• Takamori Yoshiyuki
• Noie Akihiko
• Araki Chieko
• Naoe Kazuaki
• Amasaki Shimpei

Classifications

• H01M4/13

  Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof · CPC title

• H01M4/131

  Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx · CPC title

• H01M10/058

  Construction or manufacture · CPC title

• H01M4/133

  Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx · CPC title

• H01M10/052

  Li-accumulators · CPC title