Methods of making separators for lithium ion batteries

Patent metadata

Field	Value
Publication number	US-10056590-B2
Application number	US-201615253052-A
Country	US
Kind code	B2
Filing date	Aug 31, 2016
Priority date	Aug 31, 2016
Publication date	Aug 21, 2018
Grant date	Aug 21, 2018

Abstract

Methods for producing a battery separator are provided. The methods include applying a liquid precursor material to a substrate to generate a coating layer on the substrate. The liquid precursor material includes a polymer, and a first solvent. The methods also include precipitating the polymer from the liquid precursor material in the coating layer to form a polymer membrane, and drying the polymer membrane to generate a battery separator.

First claim

What is claimed is:

1. A method of producing a battery separator, the method comprising:
applying a liquid precursor material to a substrate to generate a coating layer on the substrate, wherein the liquid precursor material comprises:
a polymer having a cohesive energy of greater than or equal to about 100,000 J/mol, a melting temperature of greater than or equal to about 300° C., a glass transition of greater than or equal to about 200° C., and a molecular weight of greater than or equal to about 10,000 g/mol; and
a first solvent;

precipitating the polymer from the liquid precursor material in the coating layer to form a polymer membrane; and
drying the polymer membrane to generate the battery separator.

2. The method according to claim 1 , wherein the polymer is poly(m-phenyl ene-isophthalamide), poly(p-phenylene-terephthalamide, polyimide, polysulfone, or a combination thereof.

3. The method according to claim 1 , wherein the first solvent is N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dimethylformamide (DMF) and optionally contains CaCl 2 , LiCl, or both CaCl 2 and LiCl.

4. The method according to claim 1 , wherein the liquid precursor material further comprises a second solvent selected from the group consisting of acetonitrile, tetrahydrofuran (THF), ethyl acetate, and combinations thereof, and the method further comprises, after the applying and before the precipitating, evaporating the second solvent.

5. The method according to claim 4 , wherein the liquid precursor material further comprises a non-solvent comprising water, acetone, alcohol, or a combination thereof, and wherein the precipitating the polymer from the liquid precursor material in the coating layer is performed by the evaporating the second solvent.

6. The method according to claim 1 , wherein the polymer has a concentration of greater than or equal to about 5% to less than or equal to about 40% by weight based on the first solvent.

7. The method according to claim 1 , wherein the substrate is a solid film substrate and the method further comprises:
separating the solid film substrate from the polymer membrane during or after the precipitating the polymer from the liquid precursor material.

8. The method according to claim 1 , wherein the substrate is a woven fiber mat, a non-woven fiber mat, polyolefin separator or a polyolefin porous membrane, and the applying a liquid precursor material to the substrate comprises applying a liquid precursor material to one side or two opposing sides of the substrate.

9. The method according to claim 1 , wherein the battery separator has a uniform distribution of pores, the pores having an average diameter of less than or equal to about 10 μm, and wherein the battery separator has a porosity of from greater than or equal to about 20% to less than or equal to about 80%.

10. The method according to claim 1 , wherein the applying a liquid precursor material to a substrate to generate a coating layer on the substrate is performed by die coating or spray coating.

11. The method according to claim 1 , wherein the precipitating a polymer from the liquid precursor material in the coating layer is performed by conditioning the coating layer in a controlled environment having a humidity of greater than or equal to about 50% to less than or equal to about 100% and a temperature of greater than or equal to about 20° C. to less than or equal to about 50° C.

12. A method of producing a battery separator, the method comprising:
applying a liquid precursor material to a solid film substrate to generate a coating layer on the solid film substrate, wherein the liquid precursor material comprises:
a polymer having a cohesive energy of greater than or equal to about 100,000 J/mol; a melting temperature of greater than or equal to about 300° C., a glass transition of greater than or equal to about 200° C., and a molecular weight of greater than or equal to about 10,000 g/mol;
a first solvent; and
a second solvent having a higher volatility than the first solvent;

evaporating a portion of the second solvent;
precipitating the polymer from the liquid precursor material in the coating layer to form a polymer membrane;
rinsing the polymer membrane to remove the first solvent and any residual second solvent; and
removing the solid film substrate from the polymer membrane, wherein the polymer membrane is the battery separator.

13. The method according to claim 12 , wherein the liquid precursor material further comprises ceramic particles, wherein the ceramic particles are nano-sized silica particles, micron-sized alumina particles, sub-micron-sized alumina particles or a combination thereof.

14. The method according to claim 12 , wherein the film substrate is a metal foil or a polyethylene terephthalate (PET) thin film.

15. The method according to claim 12 , wherein the battery separator has a shrinkage after being exposed to about 120° C. for 1 hour of less than or equal to about 5%.

16. A method of producing a battery separator, the method comprising:
applying a liquid precursor material to at least one side of a substrate to generate at least one coating layer on the substrate, wherein the substrate is a porous mechanical reinforcement selected from the group consisting of a woven fiber mat, a non-woven fiber mat, a polyolefin separator, and a polyolefin porous membrane, and the liquid precursor material comprises:
a polymer having a cohesive energy of greater than about 100,000 J/mol; a melting temperature of greater than about 300° C., a glass transition of about 200° C., and a molecular weight of greater than about 10,000 g/mol;
a first solvent; and
a second solvent having a higher volatility than the first solvent;

evaporating a portion of the second solvent;
precipitating the polymer from the liquid precursor material in the at least one coating layer to form at least one polymer laminate layer; and
rinsing the at least one polymer laminate layer to remove the first solvent and any residual second solvent and to thereby form the battery separator comprising the substrate and the at least one polymer laminate layer.

17. The method according to claim 16 , wherein the first solvent is N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), or dimethylformamide (DMF) and the liquid precursor material further comprises:
a non-solvent selected from the group consisting of water, acetone, alcohol, and combinations thereof, and
wherein the precipitating is performed during the evaporating the second solvent.

18. The method according to claim 16 , wherein the battery separator has a tensile strength of greater than or equal to about 15 MPa.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Huang Xiaosong
• Ellison Nicole D

Classifications

• B29C41/02 Primary

  for making articles of definite length, i.e. discrete articles · CPC title

• H01M50/451

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

• H01M50/494

  Tensile strength · CPC title

• H01M50/417

  Polyolefins · CPC title

• H01M50/491

  Porosity · CPC title