Method for producing a lithium ion secondary battery

Patent metadata

Field	Value
Publication number	US-10770746-B2
Application number	US-201515544623-A
Country	US
Kind code	B2
Filing date	Mar 19, 2015
Priority date	Mar 19, 2015
Publication date	Sep 8, 2020
Grant date	Sep 8, 2020

Abstract

A method for producing a lithium ion secondary battery in which a positive electrode, a heat-resistant insulating layer provided separator having a heat-resistant insulating layer formed of oxide particles on one surface of a resin porous substrate, and a negative electrode are laminated on one another, and a nonaqueous electrolyte is impregnated in the heat-resistant insulating layer provided separator, includes drying the heat-resistant insulating layer provided separator before laminating so that the water content in the heat-resistant insulating layer provided separator remains in a predetermined range. In the drying, the water content in the heat-resistant insulating layer provided separator is decreased to the predetermined range by controlling the dew point and maintaining the predetermined range after reaching the predetermined range of water content.

First claim

The invention claimed is:

1. A method for producing a lithium ion secondary battery in which a positive electrode, a heat-resistant insulating layer provided separator having a heat-resistant insulating layer formed of oxide particles on one surface of a resin porous substrate, and a negative electrode are laminated on one another, and a nonaqueous electrolyte is impregnated in the heat-resistant insulating layer provided separator, comprising:
drying the heat-resistant insulating layer provided separator before laminating so that a water content in the heat-resistant insulating layer provided separator remains in a predetermined range,
wherein, in the drying, the water content in the heat-resistant insulating layer provided separator is decreased to the predetermined range by controlling a dew point and maintaining the predetermined range after reaching the predetermined range of the water content, and
wherein, in the drying, the heat-resistant insulating layer provided separator is dried by setting the dew point so as to attain a water content decrease rate such that a shape of the heat-resistant insulating layer provided separator after the drying defined by a length ratio Y that is a ratio of a length of the resin porous substrate to a length of the heat-resistant insulating layer satisfies an equation:
1−4π X≤Y≤ 1+4π X,

wherein D represents a thickness of the separator, L represents a length of the separator, and X represents a ratio (D/L) of the thickness D to the length L of the separator,
wherein, in the drying, the water content is decreased such that a water decrease rate ((1−W)/T) satisfies an equation:
((1− W )/ T )≤1.2, and

wherein W is a water content ratio W=w2/w1, T is a drying time of 0.5 hour, w1 is a water content before starting the drying, and w2 is a water content that is measured when T elapses after starting the drying.

2. The method for producing a lithium ion secondary battery according to claim 1 , wherein, in the drying step, the heat-resistant insulating layer provided separator is dried such that the water content to remain in the predetermined range is controlled to satisfy an equation:
0.4≤ W< 1.

3. The method for producing a lithium ion secondary battery according to claim 1 , wherein the lithium ion secondary battery comprises a ratio of a battery cell area to rated capacity is 5 cm 2 /Ah or more, and the rated capacity is at least 3 Ah or more.

Assignees

• Envision Aesc Japan Ltd

Inventors

• Matsuzaki Ikuma
• Miyatake Kazuki
• Matsumoto Keisuke
• Nagano Kodai

Classifications

• H01M50/443

  Particulate material · CPC title

• H01M50/451 Primary

  comprising layers of only organic material and layers containing inorganic material · CPC title

• Y02P70/50

  Manufacturing or production processes characterised by the final manufactured product · CPC title

• H01M10/058

  Construction or manufacture · CPC title

• H01M10/052 Primary

  Li-accumulators · CPC title