Method For Manufacturing Crosslinked Structure-Containing Separator For Lithium Secondary Battery, Crosslinked Structure-Containing Separator For Lithium Secondary Battery Obtained Thereby, And Lithium Secondary Battery Including The Same

Patent metadata

Field	Value
Publication number	US-2024222787-A1
Application number	US-202218289206-A
Country	US
Kind code	A1
Filing date	May 9, 2022
Priority date	May 7, 2021
Publication date	Jul 4, 2024
Grant date	—

Abstract

The present disclosure relates to a method for manufacturing a crosslinked structure-containing separator for a lithium secondary battery, including the steps of: preparing a polyolefin porous support including a photoinitiator; and irradiating ultraviolet rays to the polyolefin porous support, wherein the polyolefin porous support has a BET specific surface area of 10-27 m 2 /g, and the content of the photoinitiator is 0.01-1.0 mg/m 2 based on the specific surface area of the polyolefin porous support. The present disclosure also relates to a crosslinked structure-containing separator for a lithium secondary battery obtained from the method, and a lithium secondary battery including the crosslinked structure-containing separator for a lithium secondary battery. The polyolefin porous support has a controlled BET specific surface area so that it may be crosslinked even with a small amount of photoinitiator.

First claim

1 . A method for manufacturing a crosslinked structure-containing separator for a lithium secondary battery, comprising:
preparing a polyolefin porous support comprising a photoinitiator; and irradiating ultraviolet rays to the polyolefin porous support, wherein the polyolefin porous support has a BET specific surface area of 10-27 m 2 /g, and a content of the photoinitiator is 0.01-1.0 mg/m 2 based on the specific surface area of the polyolefin porous support.

2 . The method according to claim 1 , wherein the preparing the polyolefin porous support comprises:
supplying polyolefin and a liquid diluting agent to an extruder; extruding a polyolefin composition from the extruder; passing the extruded polyolefin composition through a die and a cooling roll to mold and orient in the form of an oriented sheet; extracting the liquid diluting agent from the oriented sheet to obtain a preliminary porous support; thermally fixing the preliminary porous support to obtain the polyolefin porous support having the BET specific surface area of 10-27 m 2 /g; and coating and drying a photo-crosslinking composition including the photoinitiator and a solvent to the outer side of the polyolefin porous support.

3 . The method according to claim 2 , wherein the liquid diluting agent has a kinematic viscosity at 40° C. of 25-100 cSt.

4 . The method according to claim 2 , wherein the cooling roll has a temperature of 30-65° C.

5 . The method according to claim 2 , wherein the thermally fixing is carried out at a temperature of 125-132° C.

6 . The method according to claim 2 , wherein the photo-crosslinking composition is a photoinitiator solution comprising the photoinitiator and the solvent.

7 . (canceled)

8 . The method according to claim 2 , wherein the step of coating and drying the photo-crosslinking composition comprises:
coating a slurry comprising an inorganic filler, a first binder polymer and a dispersion medium on at least one surface of the polyolefin porous support, followed by drying, to form an inorganic composite porous layer; and applying a coating solution comprising a second binder polymer, the photoinitiator and the solvent to the top surface of the inorganic composite porous layer, followed by drying, to form a porous adhesive layer.

9 . The method according to claim 1 , wherein the photoinitiator comprises a Type 2 photoinitiator.

10 . The method according to claim 1 , wherein the photoinitiator comprises thioxanthone (TX), a thioxanthone derivative, benzophenone (BPO), a benzophenone derivative, or two or more of them.

11 . The method according to claim 1 , wherein the ultraviolet rays are irradiated at a dose of 10-2000 mJ/cm 2 .

12 . A crosslinked structure-containing separator for a lithium secondary battery obtained by the method as defined in claim 1 .

13 . A crosslinked structure-containing separator for a lithium secondary battery, comprising a crosslinked structure-containing polyolefin porous support having a crosslinked structure comprising polymer chains interconnected directly with one another, wherein the crosslinked structure-containing polyolefin porous support has a BET specific surface area of 10-27 m 2 /g.

14 . The crosslinked structure-containing separator according to claim 13 , wherein the crosslinked structure-containing polyolefin porous support has an average pore size of 30-80 nm.

15 . The crosslinked structure-containing separator according to claim 13 , wherein the crosslinked structure-containing polyolefin porous support has a porosity of 45-70%.

16 . The crosslinked structure-containing separator according to claim 13 , wherein the crosslinked structure-containing polyolefin porous support has a crosslinking degree of 10-45%.

17 . The crosslinked structure-containing separator according to claim 13 , further comprising an inorganic composite porous layer disposed on at least one surface of the crosslinked structure-containing polyolefin porous support, wherein the inorganic composite porous layer comprises an inorganic filler and a binder polymer.

18 . The crosslinked structure-containing separator according to claim 13 , further comprising:
an inorganic composite porous layer disposed on at least one surface of the crosslinked structure-containing polyolefin porous support, and a porous adhesive layer disposed on the inorganic composite porous layer, wherein the inorganic composite porous layer comprises an inorganic filler and a first binder polymer; and the porous adhesive layer comprises a second binder polymer.

19 . The crosslinked structure-containing separator according to claim 13 , which has a meltdown temperature of 160° C. or higher.

20 . The crosslinked structure-containing separator according to claim 13 , which has a shutdown temperature of 145° C. or less.

21 . A lithium secondary battery comprising a positive electrode, a negative electrode and a separator for a lithium secondary battery interposed between the positive electrode and the negative electrode, wherein the separator for a lithium secondary battery is the crosslinked structure-containing separator of claim 13 .

Assignees

• Lg Chemical Ltd

Inventors

• Lee Joo-Sung
• Mun Sung Cik
• Han Sung-Jae
• Kim Bong-Tae
• Jung Kil-An

Classifications

• H01M50/491

  Porosity · CPC title

• H01M50/446

  Composite material consisting of a mixture of organic and inorganic materials · CPC title

• H01M50/417

  Polyolefins · CPC title

• H01M50/451

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

• H01M50/489

  Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties · CPC title