# US 11,444,306 B2 · Composite membranes for flow batteries

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- Number: US 11,444,306 B2
- Document ID: US11444306B2
- Status: Granted
- Kind: B2
- Application number: 17/099,096
- Filed: 2020-11-16
- Published: 2021-07-08
- Granted: 2022-09-13
- Earliest claimed: 2016-02-26
- Assignees: Case Western Reserve University
- Applicants: Case Western Reserve University
- Inventors: Jesse S. Wainright; Gary E. Wnek; Enoch A. Nagelli; Robert Savinell
- Web page: https://patentgrep.com/patent/US11444306B2

## CPC

- H01M 8/188: {by recharging of redox couples containing fluids; Redox flow type batteries}
- H01B 1/122: {Ionic conductors}
- H01M 4/8657: {layered}
- H01M 2300/0091: in the form of mixtures
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01B: CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES (selection for magnetic properties H01F1/00; waveguides H01P {; printed circuits H05K})
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A composite membrane for use in flow batteries is contemplated. The membrane comprises a hydrogel, such as poly(vinyl alcohol), applied to a polymeric microporous film substrate. This composite is interposed between two half cells of a flow battery. The resulting membrane and system, as well as corresponding methods for making the membrane and making and operating the system itself, provide unexpectedly good performance at a significant cost advantage over currently known systems.

## Claims

### Claim 1

A flow battery system comprising:
a positive electrolyte flowing through a positive reaction chamber and a negative electrolyte flowing through a negative reaction chamber, wherein at least one of the positive electrolyte and the negative electrolyte consists of an aqueous solution;
a non-ionomeric membrane comprising hydrogel impregnated into pores of a microporous polymeric substrate, said non-ionomeric membrane: (i) physically separating the positive reaction chamber from the negative reaction chamber so as to prevent any flow of fluid through the pores; (ii) being ionically conductive but resistant to hydraulic crossover; and (iii) not containing any sulfonate or carboxylate ionic groups; and
wherein the hydrogel consists of poly(vinyl alcohol).

### Claim 2 (depends on 1)

The flow battery according to claim 1, wherein the poly(vinyl alcohol) is semi-crystalline and at least 95 wt. % hydrolyzed.

### Claim 3 (depends on 1)

The flow battery according to claim 1, wherein at least one of the positive and negative electrolytes comprise a multi-valent ionic species.

### Claim 4 (depends on 1)

The flow battery according to claim 1, wherein the hydrogel effectively blocks all pores of the microporous polymeric substrate.

### Claim 5 (depends on 1)

The flow battery according to claim 1, wherein the microporous polymeric substrate consists of polyethylene, polypropylene, or combinations thereof.

### Claim 6 (depends on 1)

The flow battery according to claim 1, wherein the polymeric substrate has a void volume between 30% and 80%.

### Claim 7 (depends on 1)

The flow battery according to claim 1, wherein the polymeric substrate has a thickness of between 25 and 200 micrometers prior to being impregnated by the hydrogel.

### Claim 8 (depends on 1)

The flow battery according to claim 1, wherein the aqueous solution has a pH of less than 3.0.

### Claim 9 (depends on 1)

The flow battery according to claim 1, wherein the hydrogel is hydrolyzed and crosslinked.

### Claim 10 (depends on 1)

The flow battery according to claim 1, wherein both the positive and the negative electrolytes comprise separate aqueous solutions.

### Claim 11 (depends on 1)

The flow battery according to claim 1, wherein the non-ionomeric membrane has a conductivity greater than 0.01 S/cm relative to a 1M HCl solution.

### Claim 12 (depends on 1)

The flow battery according to claim 1, wherein the non-ionomeric membrane has a normalized hydraulic permeability of less than or equal to 9×10−12 cm2/cm.

### Claim 13 (depends on 1)

The flow battery according to claim 1, wherein the hydrogel is deposited on at least one side of the substrate at a thickness of 0.1 to 25 micrometers.

### Claim 14 (depends on 1)

The flow battery according to claim 1, wherein the hydrogel is hydrolyzed and has a purity of at least 99 wt. %.

### Claim 15 (depends on 1)

The flow battery according to claim 1, wherein the positive and negative electrolytes each comprise a multi-valent ionic species selected from ferric or ferrous ions.