# US 2020/0403202 A1 · Single-layer lithium ion battery separators exhibiting high low-shrinkage rates at high temperatures

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- Number: US 2020/0403202 A1
- Document ID: US20200403202A1
- Status: Published application
- Kind: A1
- Application number: 16/917,844
- Filed: 2020-06-30
- Published: 2020-12-24
- Earliest claimed: 2012-11-14
- Assignees: Dreamweaver International, Inc.
- Inventors: Brian G. Morin
- Web page: https://patentgrep.com/patent/US20200403202A1

## CPC

- H01M 50/44: Fibrous material
- D21H 13/02: Synthetic cellulose fibres
- D21H 13/10: Organic non-cellulose fibres
- D21H 13/24: Polyesters
- D21H 15/02: characterised by configuration
- D21H 21/52: Additives of definite length or shape
- D21H 27/00: Special paper not otherwise provided for, e.g. made by multi-step processes
- H01M 50/414: Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M 50/489: Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M 50/491: Porosity
- H01M 50/494: Tensile strength
- H01M 50/403: Manufacturing processes of separators, membranes or diaphragms
- Y02E 60/10: Energy storage using batteries
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- D21H: PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

An insulating (nonconductive) microporous polymeric battery separator comprised of a single layer of enmeshed microfibers and nanofibers is provided. Such a separator accords the ability to attune the porosity and pore size to any desired level through a single nonwoven fabric. Through a proper selection of materials as well as production processes, the resultant battery separator exhibits isotropic strengths, low shrinkage, high wettability levels, and pore sizes related directly to layer thickness. The overall production method is highly efficient and yields a combination of polymeric nanofibers within a polymeric microfiber matrix and/or onto such a substrate through high shear processing that is cost effective as well. The separator, a battery including such a separator, the method of manufacturing such a separator, and the method of utilizing such a separator within a battery device, are all encompassed within this invention.

## Claims

### Claim 1

A battery separator comprising fibers of length less than 2.54 cm (1 inch), such fibers comprising at least 5% of thermally stable fibers that have no melting point, glass transition temperature or thermal degradation below about 300° C., wherein said fibers are polymeric materials selected from the group consisting essentially of polyacrylonitriles, polyolefins, polyolefin copolymers, polyamides, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, polysulfone, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polymethyl pentene, polyphenylene sulfide, polyacetyl, polyurethane, aromatic polyamide, semi-aromatic polyamide, polypropylene terephthalate, polymethyl methacrylate, polystyrene, synthetic cellulosic polymers, polyaramids, and blends, mixtures and copolymers including said polymeric materials, wherein such battery separator exhibits no observable spectral reflectance of after application of a drop of an electrolyte on the surface thereof, wherein such battery separator has a mean flow pore size less than 2000 nm, wherein said separator allows for lithium ion transport with an electrolyte within a lithium ion battery, and wherein said separator exhibits an apparent density of at least 0.564 g/cm3.

### Claim 2 (depends on 1)

A battery separator of claim 1, said separator further comprised of a single layer of said fibers, and wherein said fiber layer includes enmeshed microfibers and nanofibers, and wherein said separator exhibits a porosity of no greater than 51%.

### Claim 3 (depends on 2)

The battery separator of claim 2, wherein said microfibers are entangled with one another; wherein said separator exhibits interstices between each entangled microfiber; and wherein said interstices include nanofibers present therein.

### Claim 4 (depends on 2)

The battery separator of claim 2 in which said microfibers comprise fibrillated microfibers.

### Claim 5 (depends on 2)

The battery separator of claim 2, wherein said microfibers have an average fiber diameter greater than 1000 nm.

### Claim 6 (depends on 2)

The battery separator of claim 2, wherein said microfibers have an average fiber diameter greater than 3000 nm.

### Claim 7 (depends on 2)

The battery separator of claim 2, wherein said nanofibers have an average fiber diameter less than 1000 nm.

### Claim 8 (depends on 2)

The battery separator of claim 2, wherein said nanofibers have an average fiber diameter less than 700 nm.

### Claim 9 (depends on 2)

The battery separator of claim 2 comprising nanofibers with a transverse aspect ratio greater than 1.5:1.

### Claim 10 (depends on 1)

The battery separator of claim 1 wherein said separator exhibits a tensile strength greater than 59 kg/cm2.