BATTERY EMPLOYING SAME

Cross-Reference to Related Applications

[0001] The present application is related to and claims priority benefits from U.S. patent application Serial No. 15/677,797 filed on August 15, 2017, entitled "Battery Separator Membrane and Battery Employing Same". The '797 application claims priority benefits, in turn, from U.S. provisional patent application Serial No. 62/492,946 filed on May 1, 2017, entitled "Rechargeable Battery".

[0002] The present application is also related to U.S. patent application Serial No. 15/090,477 filed on April 4, 2016 (now U.S. Patent No. 9,580,824 issued on February 28, 2017), entitled "Ion-Conducting Membranes". The '477 application is, in turn, a continuation-in-part of U.S. patent application Serial No. 14/704,935 filed on May 5, 2015 (now U.S. Patent No. 9,370,773 issued on June 21, 2016), entitled "Ion-Conducting Membranes". The '935 application was, in turn, a continuation-in-part of International Application No.

PCT/US2015/14328, filed on February 3, 2015 (published as International Publication No. WO 2016/064440 Al on April 28, 2016), entitled "Electrolyzer and Membranes". The '328 international application claimed priority benefits, in turn, from U.S. provisional patent application Serial No. 62/066,823, filed on October 21, 2014.

[0003] The '935 application was also a continuation-in-part of International Application No. PCT/US2015/26507, filed on April 17, 2015 (published as International Publication No. WO 2016/064447 Al on April 28, 2016), entitled "Electrolyzer and Membranes". The '507 international application also claimed priority benefits, in turn, from U.S. provisional patent application Serial No. 62/066,823 filed October 21, 2014.

[0004] This application is also related to U.S. patent application Serial No. 14/035,935, filed on September 24, 2013 (now U.S. Patent No. 9,370,773 issued on June 21, 2016), entitled "Devices and Processes for Carbon Dioxide

Conversion into Useful Fuels and Chemicals"; U.S. patent application Serial No. 12/830,338, filed on July 4, 2010 (published as U.S. Patent Application Publication No. US 2011/0237830 Al on September 29, 2011), entitled "Novel Catalyst Mixtures"; International application No. PCT/2011/030098 filed on March 25, 2011 (published as International Publication No. WO 2011/120021 on September 29, 2011), entitled "Novel Catalyst Mixtures"; U.S. patent application Serial No. 13/174,365, filed on June 30, 2011 (now U.S. Patent No. 9,566,574 issued on February 14, 2017), entitled "Novel Catalyst Mixtures"; International application No. PCT/US2011/042809, filed on July 1, 2011 (published as International Publication No. WO 2012/006240 Al on January 12, 2012), entitled "Novel Catalyst Mixtures"; U.S. patent application Serial No. 13/530,058, filed on June 21, 2012 (published as U.S. Patent Application Publication No. US 2013/0015064 Al on January 17, 2013), entitled "Sensors for Carbon Dioxide and Other End Uses"; International application No.

PCT/US2012/043651, filed on June 22, 2012 (published as International Publication No. WO 2012/177952 A2 on December 27, 2012), entitled "Low Cost Carbon Dioxide Sensors"; and U.S. patent application Serial No.

13/445,887, filed on April 12, 2012 (now U.S. Patent No. 9,012,345 issued on April 21, 2015), entitled "Electrocatalysts for Carbon Dioxide Conversion". Field of the Invention

[0005] The present invention relates to separator membranes for

electrochemical devices. In particular, the present invention relates to separator membranes for batteries and the resultant battery.

Background of the Invention

[0006] Secondary lithium ion batteries now power most portable electronic devices, but lithium is highly flammable and lithium ion batteries need replacement more frequently than is ordinarily desirable. Many alternate battery chemistries and designs have been proposed, but they have inherent

shortcomings.

[0007] Conventional alkaline batteries have been in use for many years. Alkaline batteries have reasonable energy densities, but they are difficult to recharge once fully discharged, due to zinc crossover during discharge and hydrogen formation during the recharging process.

[0008] In Lin et al., Science, 349, Issue 6255, pp. 1529-1532 (2015), a new battery is described with chemistry that avoids hydrogen formation. Lin's battery is limited, however, by the use of a separator membrane that has high resistance (approximately 0.895 ohm-cm ² at room temperature).

[0009] In Parker et al, Science 356, Issue 6336, pp. 415-418 (2017), a new battery is described that can be discharged to 40% capacity and recharged. However, zinc crossover occurs at higher discharge, limiting performance.

Summary of the Invention

[0010] Shortcomings of existing batteries are overcome by the use of a battery separator comprising an anion- conducting polymeric composition comprising a copolymer of styrene and vinylbenzyl-R _s , where R _s is a positively charged cyclic amine group.

[0011] In the foregoing improved battery separator, the ion-conducting polymeric composition preferably comprises a terpolymer of styrene, vinylbenzyl-Rs and vinylbenzyl-R _x , in which R _s is a positively charged cyclic amine group, R _x is at least one constituent selected from the group consisting of CI, OH and a reaction product between an OH or a CI and a species other than a cyclic amine or a simple amine, the total weight of the vinylbenzyl-R _x groups is greater than 0. 3% of the total weight of the membrane, and the total weight of the vinylbenzyl-Rs groups is 15% or more of the total weight of the membrane.

[0012] In one embodiment of the foregoing battery, R _s is selected from the group consisting of imidazoliums, pyridiniums, pyrazoliums, pyrrolidiniums, pyrroliums, pyrimidiums, piperidiniums, indoliums, and triaziniums, preferably imidazoliums and pyridiniums.

[0013] In another embodiment of the polymeric composition, R _s is an imidazolium. The imidazolium is preferably an alkylimidazolium, more preferably tetramethylimidazolium.

[0014] In another embodiment of the polymeric composition, R _s is a pyridinium. The pyridinium is preferably an alkylpyridinium, more preferably pentamethylpyridinium.

[0015] In another embodiment of the polymeric composition, the polymer has a molecular weight between 1000 and 10,000,000 atomic units (A.U.) preferably between 10,000 and 1,000,000 A.U., most preferably between 25,000 and 250,000 A.U.

[0016] In another embodiment, the polymeric composition is in the form of a membrane. The membrane has a preferred thickness of from 10 to 300 micrometers.

[0017] In another embodiment, the polymeric composition is crosslinked.

[0018] In another embodiment, the polymeric composition further comprises at least one constituent selected from the group consisting of:

(a) a linear or substituted polyolefm;

(b) a polymer comprising uncharged cyclic amine groups;

(c) a polymer comprising at least one of a phenylene group and a phenyl group;

(d) a polyamide; and

(e) the reaction product of a constituent having two carbon-carbon double bonds.

[0019] In another embodiment, the polyolefm comprises at least one of polyethylene, polypropylene and/or polytetrafluoroethylene. The polymer comprising uncharged cyclic amine groups is preferably polybenzimidazole. The polymer comprising at least one of a phenylene group and a phenyl group is preferably polyphenylene oxide. The constituent having two carbon-carbon double bonds is preferably divinyl benzene or butadiene. The preferred polyamide constituent is polybenzimidazole.

[0020] In another embodiment, the polymeric membrane further comprises a porous layer, wherein the pores are between 0.5 and 3 nm in diameter.

[0021] In another embodiment, the foregoing battery also comprises at least one d-block element from the periodic table. The d-block element is preferably selected from the group of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Cd, and Hg. The d-block element can be bonded to organic ligands.

[0022] In another embodiment, the polymeric membrane further comprises a clay.

[0023] In another embodiment, the polymeric membrane further comprises a zeolite.

[0024] In another embodiment, the polymeric membrane further comprises a metal oxide.

[0025] In another embodiment, the polymeric membrane further comprises a nano-filtration or ultrafiltration membrane.

[0026] In another embodiment, the polymeric membrane further comprises alternate layers of:

(a) organic molecules or polymers comprised of anionic groups; and

(b) organic molecules or polymers comprised of cationic groups.

[0027] In another embodiment, the polymeric membrane further comprises molecules or polymers than can chelate metal ions.

[0028] In another embodiment, the polymeric membrane further comprises molecules or polymers having carboxylate ligands.

[0029] In another embodiment, the polymeric membrane further comprises a cation exchange ionomer. The cation exchange ionomer preferably comprises perfluorosulfonic acid.

[0030] In another embodiment, the polymeric membrane further comprises a reverse osmosis membrane. [0031] In another embodiment the polymeric membrane comprises a polymerized positively charged cyclic amine surfactant.

[0032] Preferably, the positively charged cyclic amine surfactant is of the form: where:

Ri9- and -R21- are bifunctional groups comprising positively charged cyclic amines;

R20- is a bifunctional group selected from linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls; and

R ₁₈ and R22 are each independently selected from linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls wherein each of the mono functional groups R ₁₈ and R22 contain at least one unreacted double bond.

[0033] Preferably R^ and R21 are positively charged cyclic amines other than imidazoliums.

[0034] Preferably R ₁₈ , R20, and R22 contain no more than 20 carbon atoms.

[0035] In another embodiment, the battery separator comprises a polymerized positively charged cyclic amine surfactant . Preferably, the positively charged cyclic amine surfactant is of the form: where:

Ri9 and R21 are positively charged cyclic amines;

R20 is selected from linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls, but not polymers; and

R ₁₈ and R22 are independently selected from linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls containing an unreacted double bond.

[0036] The positively charged cyclic amines are preferably not imidazoliums. Ri8, R20, and R22 preferably contain no more than 20 carbon atoms.

Brief Description of the Drawing

[0037] FIG. 1 is a schematic diagram that broadly depicts a battery design.

Detailed Description of Illustrative Embodimentf s)

[0038] It is understood that the process is not limited to the particular methodology, protocols and reagents described herein, as these can vary as persons familiar with the technology involved here will recognize. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to limit the scope of the process. It also is to be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to "a linker" is a reference to one or more linkers and equivalents thereof known to those skilled in the art. Similarly, the phrase "and/or" is used to indicate one or both stated cases can occur, for example, A and/or B includes (A and B) and (A or B).

[0039] Unless defined otherwise, technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the process pertains. The embodiments of the process and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and/or illustrated in the

accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one embodiment can be employed with other

embodiments as the skilled artisan would recognize, even if not explicitly stated herein.

[0040] Any numerical value ranges recited herein include all values from the lower value to the upper value in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value. As an example, if it is stated that the concentration of a component or value of a process variable such as, for example, size, angle size, pressure, time and the like, is, for example, from 1 to 98, specifically from 20 to 80, more specifically from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32, and the like, are expressly enumerated in this specification. For values that are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value are to be treated in a similar manner.

[0041] Moreover, provided immediately below is a "Definitions" section, where certain terms related to the process are defined specifically. Particular methods, devices, and materials are described, although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the process.

Definitions

[0042] The term "polymer electrolyte membrane" refers to both cation exchange membranes, which generally comprise polymers having multiple covalently attached negatively charged groups, and anion exchange membranes, which generally comprise polymers having multiple covalently attached positively charged groups. Typical cation exchange membranes include proton conducting membranes, such as the perfluorosulfonic acid polymer available under the trade designation "NAFION" from E. I. du Pont de Nemours and Company (DuPont) of Wilmington, DE.

[0043] The term "anion exchange battery" as used here refers to a battery with an anion exchange membrane separating the anode from the cathode.

[0044] The term "faradaic efficiency" as used here refers to the fraction of the electrons applied to the cell that participate desired reactions.

[0045] The term "Hydrogen Evolution Reaction" also called "HER" as used here refers to the electrochemical reaction 2H ⁺ + 2e ^~ → H ₂ .

[0046] The term "Millipore water" is water that is produced by a Millipore filtration system with a resistivity of at least 18. 2 megaohm-cm.

[0047] The term "imidazolium" as used here refers to a positively charged ligand containing an imidazole group. This includes a bare imidazole or a substituted imidazole. Ligands of the form: where Ri- R ₅ are each independently selected from hydrogen, halides, linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, heteroalkylaryls, and polymers thereof, such as the vinyl benzyl copolymers described herein, are specifically included.

[0048] The term "pyridinium" as used here refers to a positively charged ligand containing a pyridine group. This includes a bare pyridine or a

substituted pyridine. Ligands of the form:

where R ₆ -Rii are each independently selected from hydrogen, halides, linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, heteroalkylaryls, and polymers thereof, such as the vinyl benzyl copolymers described herein, are specifically included.

[0049] The term "phosphonium" as used here refers to a positively charged ligand containing phosphorus. This includes substituted phosphorus. Ligands of the form:

P ⁺ (R ₁₂ Ri3Ri ₄ Ri5), where R ₁₂ -Ri5 are each independently selected from hydrogen, halides, linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, heteroalkylaryls, and polymers thereof, such as the vinyl benzyl copolymers described herein, are specifically included.

[0050] The term "positively charged cyclic amine" as used here refers to a positively charged ligand containing a cyclic amine. This specifically includes imidazoliums, pyridiniums, pyrazoliums, pyrrolidiniums, pyrroliums,

pyrimidiums, piperidiniums, indoliums, triaziniums, and polymers thereof, such as the vinyl benzyl copolymers described herein.

[0051] The term "surfactant" as use here is a molecule with a hydrophilic head group and a hydrophobic tail

[0052] The term "positively charged cyclic amine surfactant" as used here refers to a surfactant whose head group contains a positively charged cyclic amine.

[0053] The term "polymerizable positively charged cyclic amine surfactant" as used here refers to a positively charged cyclic amine surfactant whose tail group or groups contain double bonds or other groups that can be polymerized.

[0054] The term "simple amine" refers to a species of the form: where R½, R17 and R ₁₈ are each independently selected from hydrogen, linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls, but not polymers.

[0055] The term "PIM" as used here refers to a polymer with intrinsic microporosity. [0056] The term "clay" or "clay mineral" as used here refers to materials comprised of hydrous aluminum phyllo silicates.

[0057] The term "MOF" as used here refers to a metal-organic framework.

[0058] The term "d-block element" as used here refers to one or more of the following: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg.

[0059] The term "nano-filtration membrane" as used here refers to a membrane with 1 nm to 50 nm diameter pores that pass through the membrane.

[0060] The term "reverse osmosis membrane" as used here refers to a membrane designed for reverse osmosis. It is a semipermeable membrane that uses pore sizes smaller than 1 nm to remove ions, molecules and larger molecules from water and other solvents.

[0061] The term "PSTMIM Solution" as referred here refers to a solution prepared as described in Specific Example 1.

Specific Description

[0062] FIG. 1 illustrates a simple alkaline battery. The battery consists of an anode 100, a cathode 101 and a membrane electrolyte 102 interposed

therebetween. The anode is typically zinc, copper or silver. The cathode is typically a metal oxide or hydroxide such as MnO ₂ or NiOOH. During discharge the following reactions occur on the anode

Zn(s)→ Zn (aq) + 2e (1)

Zn ²⁺ (aq) + 4OH (aq)→ Zn(OH) ₄ ² (aq) (2)

while the following reaction occurs on the cathode: 2MnO ₂ (s) + H ₂ O(l) + 2e ^" → Mn ₂ O ₃ (s) + 2OFT(aq) (3)

There is also a reaction that can occur either on the anode or the cathode:

Zn(OH) ₄ ² (aq)→ ZnO(s) + H ₂ O(l) + 2OH (aq) (4)

[0063] Zinc dissolves into the KOH solution during reaction 1, and quickly reacts with hydroxides to form a dissolved complex. Some of the Zn(OH) ₄ ² complexes react on the anode, to produce a zinc oxide precipitate, but some of the Zn(OH) ₄ ² complexes diffuse through the membrane 102 and are deposited on the cathode 101 during discharge.

[0064] Recharging the battery requires the reactions to be run in reverse to redeposit metallic zinc on the anode and re-oxidize the Mn ₂ O ₃ on the cathode. The zinc that is still in the anode can be efficiently converted back to metallic zinc. Dendrite formation should be limited, and technology exists to do so. The zinc on the cathode, though, is difficult to regenerate. Running at net is required for reducing conditions to dissolve the zinc oxide on the cathode. Running at net is also required for oxidizing conditions to re-oxidize the Mn ₂ O ₃ on the cathode. This presents a problem because the zinc cannot be reduced and Mn ₂ O ₃ cannot be oxidized at the same time.

[0065] In principle, the amount of zinc that is deposited on the cathode can be limited by tailoring the separator membrane appropriately. For example, if the membrane were designed to prevent or impede the transport of Zn(OH) ₄ ² , yet permit the hydroxides to pass through the membrane, the deposition of ZnO on the cathode could be avoided, so the battery could be regenerated.

[0066] Care is required because if the membrane resistance for hydroxyl transport is too high, the battery will not be efficient. But in principle a proper separator membrane would allow a regeneratable alkaline battery to be produced.

[0067] In this application, separator membrane compositions are disclosed that exhibit low resistance for hydroxyl transport, and yet limit the transport of copper and zinc ions through the membrane.

Specific Example 1 : Production of an improved membrane for an alkaline battery

PSTMIM polymer solution preparation

[0068] The first step is to produce a polymer solution that will be referred to as a PSTMIM Polymer solution.

[0069] Step 1: Monomer purification. Inhibitor- free vinyl benzyl chloride (VBC) was prepared by adding a volume V of VBC (Dow Chemical, Midland, MI), and a volume equal to V/4 of 0.5 wt% aqueous sodium hydroxide (Sigma Aldrich, St. Louis, MO) into a separatory funnel. This was followed by agitating the funnel to mix the water and VBC, keeping the mixture still until it formed organic and inorganic layers, and then subsequently decanting the VBC. The process was repeated until the water layer did not show visible color change, which was about five times. The procedure was repeated using deionized water instead of sodium hydroxide solution until the water layer pH was neutral. Washed VBC was placed into a freezer overnight before weighing, to convert residual water to mainly ice, and the ice was then separated from the VBC by decantation.

[0070] Step 2: Preparation of inhibitor styrene. Inhibitor-free styrene was prepared by feeding styrene (Sigma Aldrich, St. Louis, MO) through a 60-mL syringe packed with Sigma- Aldrich 311340 Inhibitor remover. [0071] Step 3: Synthesis of copolymer. Poly(vinylbenzyl chloride-co- styrene) was then synthesized by heating a solution of inhibitor-free styrene (689 g, 6.62 mol) and vinylbenzyl chloride (573 g, 3.75 mol) in chlorobenzene (999 g) at 60 ± 2°C in a heating mantle for 24 hours under nitrogen gas with AIBN (a, a'-Azoisobutyronitrile) (Sigma Aldrich, St. Louis, MO) (11.85 g, 0.94 wt% based on the total monomers weight) as initiator. The copolymer, poly(VBC-co-St), was precipitated in methanol, then washed thoroughly and dried at 60°C overnight.

[0072] Step 4: PSTMIM solution preparation. 1,2,4,5- tetramethylimidazole (172.8 g, 1.3914 mol), (TCI, Montgomeryville, PA) above-synthesized poly(VBC-co-St) (550 g), anhydrous methoxy-iso-propanol (MIP) (1600 g, Sigma- Aldrich), divinylbenzene (DVB) (Sigma Aldrich, St. Louis, MO) (22 g, 0.169 mol) and AIBN (0.22 g) were mixed under the protection of nitrogen flow. The mixture was stirred and heated to 65 °C for about 48 hours until viscosity reached around 800 cp. The resulting solution is referred to here as a "PSTMIM solution".

PSTMIM membrane preparation

[0073] The PSTMIM membranes were prepared by casting the PSTMIM polymer solutions prepared above directly onto a polyethylene terephthalate (PET) liner (LOPAREX LLC, Eden, NC). The thickness of the solution on the liner was controlled by a BKY (Geretsried, Germany) Automatic Film

Applicator with an adjustable doctor blade. The membranes were then dried in a vacuum oven with temperature increased to 70°C and held for 1 hour. After one more hour in the vacuum oven with temperature slowly decreased, the membrane was taken out of the oven and put inside a 1 M KOH (City

Chemicals, West Haven, CT) solution overnight, during which time the membrane fell from the liner. The KOH solution was changed twice. In that way, the "chloride form" anion exchange membranes were converted into the hydroxide form.

[0074] U.S. Patent Application Publication No. US 2017/0128930 Al discloses that membranes prepared in this way comprise a terpolymer of styrene, vinylbenzyl-R _s and vinylbenzyl-R _x , in which R _s is a positively charged cyclic amine group, and R _x is at least one constituent selected from the group consisting of CI, OH and a reaction product between an OH or a CI and an inorganic species or an organic species other than an amine.

[0075] Examples of inorganic species include metal ions in the starting materials. Example of the organic species include the alcohols used as solvents or otherwise added during the synthesis.

[0076] U.S. Patent Application Publication No. US 2017/0128930 Al also discloses that superior properties are obtained when the total weight of the vinylbenzyl-Rx groups is greater than 1% of the total weight of the terpolymer, and the total weight of the vinylbenzyl-R _s groups is 15% or more of the total weight of the terpolymer.

Membrane characterization

Membrane conductivity measurement

[0077] The through-plane conductivity of the membrane was tested by measuring the electrochemical impedance spectrum (EIS) of a 5 cm ² Fuel Cell Technologies (Albuquerque, NM) cell with a platinum catalyst cathode, an IrO ₂ catalyst anode and a membrane to be tested in between the cathode and the anode. [0078] A cathode was prepared as follows: 100 mg of Pt nanoparticles (Premion, Alpha Aesar) were suspended in 2 ml of isopropanol, 1 ml of deionized water and 0.2 ml of 5% dispersion of ionomer available under the trade designation NAFION (DuPont.) The mixture was ultrasonicated in a water bath for 10 minutes. The resulting cathode ink was spray coated onto a 5 cm x 5 cm section of Sigracet 39 BC carbon paper (SGL Group, Meitingen, Germany). The electrode was dried at 80°C for 20 minutes in an oven and cut into 4 pieces of 2.5 cm x 2.5 cm for testing. The catalyst loading was about 2 mg/cm ² .

[0079] An anode was prepared in a similar way but with IrO ₂ nanoparticles (Premion, Alfa Aesar,) instead of platinum nanoparticles. The catalyst ink was spray coated onto 6 cm x 6 cm stainless steel fiber cloth (AISI 316L-WNR, Bekaert, Zwevegem, Belgium.) The electrode was dried at 80°C for 20 minutes in an oven and cut into 4 pieces of 3 cm x 3 cm for testing. The actual loading was about 2 mg/cm ² .

[0080] The membrane prepared above was sandwiched between the Pt cathode and IrO ₂ anode as described above, and mounted into 5 cm ² fuel cell hardware (Fuel Cell Technologies, Albuquerque, NM), 1 M KC1 was pumped into the anode and cathode and the Electrochemical Impedance Spectrum of the cell was measured with a potentiostat coupled with a frequency analyzer (Solartron, 1287+1255B). The cell resistance was assumed to be the membrane resistance, neglecting the contributions of resistance from other components such as electrodes and cell hardware. The area specific resistance (R) was determined by the intersection of the EIS spectrum on the real axis.

[0081] Table 1 shows area specific resistances (ASR) that were measured as described above. Table 1

Specific resistances ( ASR) that were measured

^J Lin et al., Science, 349, Issue 6255, pp. 1529-1532 (2015).

[0082] It should be noted that the area specific resistance of the new

membranes is less than one-third of that of Lin et al. Consequently, the energy loss will be less. Leakage currents are also smaller, further improving the performance of the new membranes.

Cu and Zn crossover measurements

[0083] The rate of crossover of Cu ²⁺ ions through the membrane was also measured. The following method was employed to measure the limiting current:

[0084] The membrane was sandwiched between one piece of stainless steel fiber felt (cathode) and one piece of Cu mesh (anode), and mounted in a 5 cm ² Fuel Cell Technologies (Albuquerque, NM) fuel cell hardware. A I M CuSO ₄ solution was prepared by dissolving CuSO ₄ (Sigma Aldrich, St. Louis, MO) in Millipore water. CuSO ₄ solution was fed to the anode flow field and de-ionized (DI) water was fed to the cathode flow field. The Cu ²⁺ crossed through the membrane from anode to cathode was reduced to Cu° at the cathode while the Cu anode dissolved into the anolyte to maintain constant concentration of Cu ²⁺ during the measurements. The current was limited by the permeability of Cu through the membrane. A linear sweep voltammogram (LSV) was conducted by scanning the potential from 0.05 to -0.3 V at 2 mV/s. The limiting current density appeared at -0.2 to -0.3 V. The limiting current density was used as a measure of Cu ²⁺ crossover through the membrane.

[0085] The rate of crossover of Zn ²⁺ ions through the membrane was also measured. The following method was employed to measure the limiting current:

[0086] The membrane was sandwiched between one piece of silver

membrane (cathode) and one piece of copper mesh (anode), and mounted in a 5 cm ² Fuel Cell Technologies fuel cell hardware. A I M ZnNO ₃ solution was prepared by dissolving ZnNO ₃ (Sigma Aldrich, St. Louis, MO) in Millipore water. ZnNO ₃ solution was fed to the anode flow field and DI water was fed to the cathode flow field. The Zn ²⁺ crossing through the membrane from anode to cathode was reduced to Zn° at the cathode. The current was limited by the permeability of Zn ²⁺ through the membrane. The linear sweep voltammogram (LSV) was conducted by scanning the potential from -1.0 to -1.5 V at 2 mV/s. The limiting current density appeared at -1.3 to -1.4 V.

[0087] Table 2 shows the results that were obtained. Notice that the limiting Cu ²⁺ current was only 10 mA/cm ² . This compares to hydroxide currents reported in co-owned U.S. patent application Serial No. 15/406,909 above of 1,000 mA/cm ² .

Table 2

Comparison of the properties of the membranes considered here Comparative Example 1: Amine coated Targray membrane

[0088] Measurements were also performed using an amine coated Targray (Kirkland, Canada) battery separator. Most battery separators have a high resistance in 1 M KOH. Conductivities as low as 0.1 mS/cm were measured with commercial battery separators. The ceramic coated porous polypropylene membrane was an exception. When a ceramic coated porous polypropylene separator was coated with an amine surfactant, reasonable conductivities were obtained for a few hours before the amine washed away.

[0089] In detail, a 25 μΜ thick ceramic coated porous polypropylene separator #SH624w22VVV (Targray, Montreal, Canada) membrane was soaked for two minutes in a solution containing 1 wt% BIO-SOFTR N-300 (Stephan Company, Northfield, IL). The other 99% of the solution was composed of 30% deionized water and 70% by weight isopropanol (Sigma Aldrich, St. Louis, MO). The membrane was subsequently dried in an oven at 60°C for 1 hour before use.

[0090] Next, the copper and zinc crossovers, and the membrane conductivity, were measured using the procedures in Specific Example 1.

[0091] A figure of merit (FOM) for a given membrane is defined as:

FOM =

(Membrane conductivity)(polypropylene crossover current)(polypropylene thickness) (Membrane crossover current) (Initial polypropylene conductivity)(membrane thickness)

Table 2 shows the figure of merit for several examples. Specific Example 2: Effect of membrane reinforcement

[0092] The objective of this example was to demonstrate that adding one constituent selected from the group consisting of:

(a) a linear or substituted polyolefm;

(b) a polymer comprising cyclic amine groups;

(c) a polymer comprising at least one of a phenylene group and a phenyl group; and

(d) a polyamide

to the membrane reduces the crossover of the membrane.

[0093] A membrane was prepared as follows:

[0094] Step 1. A PSTMIM solution was prepared as described in Specific Example 1.

[0095] Step 2. The PSTMIM solution was diluted to 20% solids with ethanol.

[0096] Step 3. A BKY (Geretsried, Germany) Automatic Film Applicator L was used to cast a thin film of the polymer solution onto a polypropylene backing sheet (Home Depot, Atlanta, GA) using a doctor blade. The solution was allowed to dry in ambient environment for 30 minutes to yield an

approximately 15 micrometer thick polymer film.

[0097] Step 4. Next a 10 μπι thick porous expanded polytetrafluoroethylene (ePTFE) film (Philips Scientific Inc., Rock Hill, SC) was submerged for 30 minutes in a bath of ethanol to activate its surface for better wettability. (The porous ePTFE film was laid carefully taut over the deposited polymer film. The ePTFE film was also stretched in both x and y directions to fully open its pore structure as it was laid over the polymer film. [0098] Step 5. A 15 μπι layer of the PSTMIM polymer solution was deposited on top of the ePTFE. The polymer film was left to settle for 15 minutes in ambient conditions before the whole reinforced membrane was placed in an oven at 65°C for 60 minutes to improve adhesion of the polymer with the ePTFE. After the heating step, the membrane was then separated from the polypropylene backing sheet with the help of a razor blade and tweezers, and then activated as described in Specific Example 1.

[0099] Next, the copper and zinc crossovers and the conductivity were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0100] Many other support materials can be used. In general, the support material can be made of

(a) a linear or substituted polyolef n;

(b) a polymer comprising cyclic amine groups;

(c) a polymer comprising at least one of a phenylene group and a phenyl group; or

(d) a polyamide.

[0101] The support material can be simply added to the polymer solution as described in co-owned U.S. Patent No. 9,370,773. The support material can include a woven or non-woven material bonded or laminated to one side of the base material or ideally the support material can be sandwiched between an anion exchange polymer from both sides. Suitable woven materials can include, for example, scrims made of woven fibers of expanded porous

polytetrafluoroethylene (ePTFE); webs made of extruded or oriented

polypropylene or polypropylene netting or porous battery separators such as those supplied by Targray and Celgard.

Specific Example 3: Effects of crosslinking

[0102] The objective of this example was to demonstrate that adding crosslinks reduces the metal crossover of the membrane. In particular, membranes containing the reaction product of a constituent having two carbon- carbon double bonds are shown to have reduced crossover.

[0103] A Membrane was prepared as follows:

[0104] Step 1. Poly(vinylbenzyl chloride-co-styrene) was prepared as described in Specific Example 1.

[0105] Step 2. 1,2,4,5-tetramethylimidazole (3.30 g, 0.0266 mol), above- synthesized poly(VBC-co-St) (10 g), methoxy-iso-propanol (32 g, Sigma- Aldrich), divinylbenzene (DVB) (1.0 g, 0.0147 mol) and AIBN (0.008 g) were mixed under the protection of nitrogen flow. The mixture was stirred and heated to 75 °C for about 48 hours to obtain a crosslinked polymer solution containing the reaction product of a constituent having two carbon-carbon double bonds.

[0106] The crosslinked polymer solution was cast and activated followed the same procedure as in Specific Example 1 to yield a film for testing.

[0107] Next, the copper and zinc crossovers and the conductivity were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is similar to that of Specific Example 1.

[0108] Many other molecules could be used to crosslink the polymer.

Examples include (a) molecules with two or multiple carbon-carbon double bonds such as 1,3 -butadiene, isoprene, l,3,5~heptatriene, 1,3,5-trivinylbenzene, 1,3,5 -triethyl-2,4, 6-trivinylbenzene, 5 -methyl- 1 ,3 -cy clohexadiene, methylenebisacrylamide; (b) amines and diamines compounds, such as methylamine, ethylamine, Ν,Ν,Ν',Ν'-tetraacetylethylenediamine, 3(or 4),4'- diamino-biphenyl, 2,2'-diamino-biphenyl, 4,4'-oxydianiline, dipyridine; (c) azido compounds such as 2,6-bis(4-azidobenzylidene)cyclohexanone, 3-(4- azidophenyl)propionitrile or adipic acid dihydrazone; (d) halogenated or multiple halogenated compounds such as α,α'-dichloro-p-xylene, dibromo methylbenzene, tribromomethyl benzene; (e) dual functional compounds containing above functional groups, such as vinyl pyridine, vinyl imidazole, 3- azido-l-pronamine, 1 l-azido-3,6,9-trioxaundecan-l -amine

Specific Example 4: Porous polymers

[0109] The objective of this example was to demonstrate that adding a layer of a nanoporous polymer with pores between 0.5 and 3 nm in diameter reduces the metal crossover of the membrane.

[0110] PIM-1 was chosen to demonstrate this phenomenon. PIM-1 has a random structure with pores between 0.5 and 3 nm.

[0111] PIM-1 was synthesized using chemicals obtained from Sigma- Aldrich and used directly without further treatment except as described otherwise. The procedure was carried out as follows;

[0112] PIM-1 was obtained by polymerization of 0.68084 g (2 mmol) 3,3,3',3'-tetramethyl-l,r-spirobiindane-5,5',6,6'-tetraol (TTSBI, purified by re- cry stalization in methanol) and 0.4 g (1.999 mmol) tetrafluoroterephthalonitrile (TFTPN) in 4 g l-methyl-2-pyrrolidinone (NMP) containing 0.648 g (4.69 mmol) potassium carbonate (K2CO3) under nitrogen flow at 135-150°C for 2 hours. After dilution with N-methyl-2-pyrrolidone (NMP), the polymer was precipitated into Millipore water and washed thoroughly, then dried in a vacuum oven at 80 °C overnight.

[0113] Next, PIM-1 was coated onto a membrane prepared as in Specific Example 1. First a 0.2% PIM-1 solution in chloroform was prepared by dissolving 0.03 g PIM-1 prepared above in 15 ml chloroform. Then, the solution was poured on the surface of the flat PSTMIM membrane prepared according to the method in Specific Example 1. Next, the resultant wet membrane was hung vertically in air to remove excess PIM solution. And then dried in oven at 60°C for 2 hours. The membrane was then activated as described in Specific Example 1.

[0114] Next, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0115] Other polymers or polymer membranes with pore sizes between 1 and 3 nm can also be employed. Examples include the PIM's described in

McKeown, International Scholarly Research Network Materials Science, Volume 2012, Article ID 513986, and the Hyper-Cross-Linked Polymers, Covalent Organic Frameworks, Conjugated Microporous Polymers, Covalent Triazine Frameworks, Porous Aromatic Frameworks, Extrinsic Porous

Molecules, and Porous Organic Cages described in Das et al. Chem. Rev., 2017, 117 (3), pp 1515-1563.

Specific Example 5: Addition of a clay layer

[0116] The objective of this example was to demonstrate that adding a layer containing a clay reduces the metal crossover of the membrane.

[0117] A membrane was prepared as follows: [0118] Step 1. A PSTMIM polymer solution was prepared as described in Specific Example 1.

[0119] Step 2. A thin film (~ 15 μπα) of PSTMIM polymer was cast on a polypropylene backing sheet from a polymer solution prepared as in Specific Example 1. The solution was allowed to dry in ambient environment for 30 minutes.

[0120] Step 3. A clay solution was prepared by mixing K10 Montmorillonite (Sigma Aldrich, St. Louis, MO) via sonicating 10 ml of polymer solution (prepared, as described in Specific Example 1) to make a 5% by weight clay- suspension.

[0121] Step 4. A 15 μπι thick layer of the Montmorillonite film w as deposited on top of the film produced in step 2. The fi lm was dried 30 minutes under ambient conditions.

[0122] Step 5. A 15 μπι thick layer of PSTMIM was finally deposited on-top of the film from step 4 using the procedures in Specific Example 1 to create a sandwich structure.

[0123] The membrane was then dried and activated as described in Specific Example 1. Next, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0124] Other clays can perform similarly. Examples include other

Montmorillonites such as K30, KSF and aluminum pillared Montmorillonites and other clays such as bentonite and functionalized bentonite used in fuel cell studies. Slurries of calcined clay and hydrite clay as described in U.S. Patent No. 4,017,324 could also perform favorably. Specific Example 6: Zeolite layer

[0125] The objective of this example was to demonstrate that adding a layer containing a zeolite (13X molecular sieve) with a pore size between 1 and 5 nm reduces the metal crossover of the membrane.

[0126] A membrane was prepared as follows:

[0127] Step 1. A PSTMIM polymer solution was prepared as described in Specific Example 1.

[0128] Step 2. A thin film of PSTMIM solution was cast on a polypropylene backing sheet from a polymer solution prepared as in Specific Example 1. The solution was allowed to dry in ambient environment for 30 minutes to yield a 15 μιη thick membrane.

[0129] Step 3. A zeolite solution was prepared by mixing molecular sieves, 13X, 2 μπι powder particles (Sigma Aldrich, St. Louis, MO) via sonication in 10 ml of polymer solution (prepared as described in Specific Example 1) to make a 5% by weight zeolite solution. Mesoporous materials such as ordered porous silica FCM-16 and Mobil Composition of Matter such as MCM-41 and MCM-48 can be similarly employed.

[0130] Step 4. A 20 μιη thick layer of the 13X molecular sieve solution was deposited on top of the film produced in step 2. The film was dried 30 minutes under ambient conditions.

[0131] Step 5. A 20 μπι thick layer of PSTMIM solution was finally deposited on- top of the film from step 4 using the procedures in Specific Example 1 to create a sandwich structure.

[0132] The membrane was then dried and activated as described in Specific Example 1. Then, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0133] Other zeolites and molecular sieve material can be used as near equal alternatives. These include organophilic molecular sieves, ammonium Y zeolites and sodium Y zeolites. Other alumino silicate minerals can be similarly used.

Specific Example 7: Addition of MOF layer

[0134] The objective of this example was to demonstrate that adding an MOF reduces the metal crossover of the membrane.

[0135] A membrane is prepared as follows:

[0136] Step 1. A PSTMIM polymer solution was prepared as described in Specific Example 1.

[0137] Step 2. A thin film of PSTMIM solution was cast on a polypropylene backing sheet from a polymer solution prepared as in Specific Example 1. The solution was allowed to dry in ambient environment for 30 minutes to yield a 15 μιη thick membrane.

[0138] Step 3. An MOF was prepared by dissolving equimolar ratios of Ζη(Νθ3)2·6Η ₂ Ο and terephthalic acid in dimethylformamide to make a solution of 8% solids. These materials were obtained from Sigma Aldrich, St. Louis, MO. The system was sealed in a hydrothermal reactor and heated at 100°C for 5 hours. After the reaction was allowed to reach room temperature, crystals were obtained by filtering off the DMF and drying at room temperature.

[0139] Step 4. An MOF solution was prepared by mixing the synthesized MOF particles via sonication in 10 ml of polymer solution (prepared as described in Specific Example 1) to make a 5% by weight MOF suspension.

[0140] Step 5. A 15 μιη thick layer of the MOF solution was deposited on top of the film produced in step 2. The film w as dried 30 minutes under ambient conditions.

[0141] Step 6. A 15 μπι thick layer of PSTMIM was finally deposited on-top of the film from step 6 using the procedures in Specific Example 1 to create a sandwich structure.

[0142] The membrane was then dried and activated as described in Specific Example 1. Then, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0143] Copper MOFs from copper nitrate can be synthesized and used from their reaction with terephthalic acid. Similarly, other MOFs can be incorporated into the membrane by either synthesis or directly purchasing from commercial sources such as Sigma Aldrich. These include those produced by BASF as well and can use other metals such as magnesium as well as other ligands networks.

Specific Example 8: Metal oxide filler

[0144] The objective of this example was to demonstrate that adding a metal oxide filler reduces the metal crossover of the membrane.

[0145] A membrane was prepared as follows

[0146] Step 1. A PSTMIM solution was prepared as in Specific Example 1. [0147] Step 2. Titanium dioxide nanoparticles (Sigma Aldrich, St. Louis, MO) were added to this polymer solution, which amounts to 15% by weight of the polymer therein. A combination of magnetic stirring and sonication was used to uniformly disperse the metal oxide particles in the solution.

[0148] Step 3. A membrane was subsequently cast and activated according to the procedure in Specific Example 1.

[0149] The membrane was then dried and activated as described in Specific Example 1. Then, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0150] Other metal -based fillers can be used. These can be based on iron (for example, magnetite), zirconium (for example, yttria stabilized zirconia and zirconium phosphates) as well as oxides and ceramics based on other metals.

Specific Example 9: Addition of nanofiltration membrane

[0151] The objective of this example was to demonstrate that the addition of a nanofiltration membrane can reduce metal ion crossover. There are two examples, one a home-made poly(phenylene oxide) (PPO) nanofiltration membrane (example 9-1) and the other using a commercial nanofiltration membrane available from 3M Company.

Specific Example 9.1: PPO nanofiltration membrane

[0152] Step 1. A PSTMIM membrane was formed on a polypropylene sheet as in Specific Example 1.

[0153] Step 2. PPO solution preparation: a weight of 0.216 g poly(2,6- dimethyl-l,4-phenylene oxide) (PPO) (Sigma Aldrich, St. Louis, MO) was dissolved into 80 ml chloroform (Sigma Aldrich, St. Louis, MO) containing 0.0432 g ethylene glycol (Sigma Aldrich, St. Louis, MO) to make a PPO/CHCL solution with a concentration of 0.27%.

[0154] Step 3. PPO coated membrane preparation: the PPO solution prepared above was poured onto the surface of the membrane prepared in step 1. The excessive solution was drained by vertically hanging the membrane in the air for 5 minutes followed by drying in oven at 60°C for 2 hours.

[0155] Step 4. The resultant PPO coated membrane was soaked in DI water overnight to release the membrane from the liner and swell the membrane before testing. During activation, ethylene glycol leached out and left pores in the PPO coating layer.

[0156] Next, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is greater than in Specific Example 1.

Specific Example 9.2: Commercial nanofiltration membrane

[0157] Step 1. A piece of about 10x 15 cm ² of 3M PES Flat sheet: 10243/18 nanofiltration membrane (3M Deutschland GmbH, Wuppertal, Germany) was taped at the edges to a PET liner with the air side facing down to the liner.

[0158] Step 2. 5 g of a PSTMIM solution prepared as in Specific Example 1 was poured onto the film from step 1 and was spread with a BKY (Geretsried, Germany) Automatic Film Applicator.

[0159] Step 3. The membrane from step 2 was dried in a vacuum oven at 70°C for 2 hours, followed by soaking overnight in deionized water to release the membrane from the liner and swell the membrane.

[0160] The membrane was then dried and activated as described in Specific Example 1. Then, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is lower than in Specific Example 1.

Specific Example 10: Alternating anionic and cationic layers

[0161] The objective of this example was to demonstrate that adding a self- assembled layer-by-layer structure consisting of anionic and cationic layers reduces the metal crossover of the membrane.

[0162] A membrane was prepared as follows:

[0163] Step 1. A PSTMIM solution was prepared as in Specific Example 1 and was cast and activated as in Specific Example 1.

[0164] Step 2. Polystyrene sulfonate acid (PSS) solution was prepared by mixing Millipore water and polystyrene sulfonate acid (Sigma Aldrich, St. Louis, MO) to create a solution containing 20 mM of polystyrene sulfonate in water.

[0165] Step 3. A poly-dially dimethyl ammonium chloride (PDDA) solution was made by mixing Millipore water and PDDA (Sigma Aldrich, St. Louis, MO) to create a solution containing 20 mM of PDDA in water.

[0166] Step 4. The membrane from step 1 was placed into the solution from step 2 for 5 minutes to create a thin layer of the polystyrene sulfonate on the membrane surface.

[0167] Step 5. The membrane from step 4 was removed from the

polysulfonate sulfonate solution, washed with Millipore water, and air dried.

[0168] Step 6. The membrane from step 5 was placed in the solution from step 3 for 5 minutes to create a thin layer of the PDDA on the membrane surface.

[0169] Step 7. The membrane from step 6 was removed from the PDAA, washed with Millipore water, and air dried.

[0170] Step 8. The membrane from step 7 was treated as in steps 4, 5, 6, and 7 to form a second layer of PSS and PDDA on the original membrane. Step 8 was repeated two more times.

[0171] Next, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0172] Other multilayers could also be used. Specific examples include alternating layers of anion exchange polymers and cation exchange polymers, alternating layers of anionic and cationic molecules, or mixtures thereof.

Specific Example 11: Addition of a chelator

[0173] The objective of this example was to demonstrate that adding ligands that can chelate the metal ions reduce the metal crossover of the membrane.

[0174] A membrane was prepared as follows:

[0175] Step 1. A membrane was prepared as in Specific Example 1.

[0176] Step 2. Poly(vinylbenzyl chloride-co-styrene) was prepared as in steps 1, 2 and 3 of Specific Example 1.

[0177] Step 3. Preparation ofPS-DIIMI: (Diimidazole): PS-DIIMI was first synthesized. A weight of 1.68 g of 2,2'-bis(4,5-dimethylimidazole) (DIIMI) (Sigma Aldrich, St. Louis, MO), 3 g of the above- synthesized poly(VBC-co-St), and 20 g N,N-dimethylformamide (DMF) were heated at 60-65°C under stirring with the protection of nitrogen flow. A time of 34 hours later, the mixture was found to be very viscous. It was diluted with 17 g DMF and the reaction was continued to a total of 37 hours.

[0178] Step 4. After cooling to room temperature, a small portion of the reaction mixture was diluted to 2-3% with DMF. Then, the diluted reaction mixture was poured on the surface of the membrane formed in step 1. The reaction mixture was then spread with a doctor blade, followed by drying in a vacuum oven at 70°C for 2 hours.

[0179] The membrane was activated as in Specific Example 1. Then, the copper crossover was measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

[0180] Other chelators with similar functions can perform similarly.

Examples include Ι, -carbonyldiimidazole, Ι, -thiocarbonyldiimidazole, 4,4'- dimethoxy-2,2 ' -bipyridine, and 2,2 ' -bipyridine-4,4 ' -dicarboxaldehyde.

Specific Example 12: Addition of carboxyl ligands

[0181] The objective of this example was to demonstrate that adding carboxyl ligands can reduce metal ion crossover.

[0182] A membrane was prepared as follows:

[0183] Step 1. A PSTMIM solution was prepared as in Specific Example 1.

[0184] Step 2. Benzene- 1,4-dicarboxylic acid (terephthalic acid) (Sigma Aldrich, St. Louis, MO) was added to this polymer solution, which amounts to 15% by weight of the polymer therein. A combination of magnetic stirring and sonication was used to uniformly disperse the terephthalic acid in the solution.

[0185] Step 3. The membrane was cast and activated according to the procedure in Specific Example 1.

[0186] Next the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is higher than in Specific Example 1.

Specific Example 13: Addition of a cation exchange polymer

[0187] The objective of this example was to demonstrate that adding a cation exchange polymer to the membrane can reduce crossover. A membrane was prepared as follows:

[0188] Step 1. A PSTMIM solution was prepared as in Specific Example 1.

[0189] Step 2. Perfluorosulfonic acid solution 1100 EW (available under the trade designation "LIQUION", item LQ-1105, from Ion Power, New Castle, DE) was mixed into 10 mL of PSTMIM solution from step 1 to make 4% by weight perfluorosulfonic acid. A combination of magnetic stirring and sonication was used to uniformly mix the two solutions.

[0190] Step 3. The 35 μπι membrane was cast and activated according to the procedure in Specific Example 1.

[0191] Next, the copper and zinc crossovers were measured using the procedures in Specific Example 1. Results are shown in Table 2. Note that the figure of merit is similar to that in Specific Example 1.

Specific Example 14: Reverse osmosis membrane

[0192] The objective of this example is to demonstrate that a reverse osmosis membrane can reduce metal crossover.

[0193] A membrane was prepared as follows:

[0194] Step 1. A PSTMIM polymer solution was prepared as in Specific Example 1.

[0195] Step 2. A thin film of the polymer from step 1 was deposited on one side of a Dow BW30XFR reverse osmosis (RO) membrane (Dow Chemical, Midland, MI) to yield a 10 μπι thick film.

[0196] Step 3. After letting the polymer film dry in ambient conditions for 30 minutes, another 10 μπι polymer film was similarly cast on the other side of the RO membrane.

[0197] Step 4. After drying for another 30 minutes in ambient conditions, the RO-polymer membrane was then activated in 1 M KOH solution as described in Specific Example 1.

[0198] Next, the copper and zinc crossovers and the conductivity were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is lower than in Specific Example 1.

[0199] Many other support reverse osmosis membranes can be used. In general, the RO membrane can be made of polyimides, polyamides,

polypropylene, and/or polyesters.

Specific Example 15: Surface modification

[0200] The object of this example was to demonstrate that adding a layer with a high concentration of positively charged species can reduce crossover.

[0201] A membrane was prepared as follows: [0202] Step 1. Synthesis of VBC polymer: a solution of inhibitor- free 3,4- vinylbenzyl chloride (100 g, 0.655 mol) in chlorobenzene (80 g) containing AIBN (0.94 g, 0.94 wt% of VBC) as initiator was heated at 60±2°C under stirring in an oil bath for 24 hours with nitrogen flow. The VBC polymer was precipitated in methanol, then washed thoroughly and dried at 60°C overnight.

[0203] Step 2. Preparation of highly positive charged PSTMIM (47%) solution: 1,2,4,5-tetramethylimidazole (4.7 g, 0.378 mol), above- synthesized VBC polymer (10 g), anhydrous methoxy-iso-propanol (MIP) (30 g), divinylbenzene (DVB) (0.4 g, 0.003 mol in 1.6 g MIP) and AIBN (0.004 g in 0.67 g MIP) were mixed under the protection of nitrogen flow with stirring and heating at 75 °C for about 26 hours.

[0204] Step 3. Two g of the solution from step 2 was diluted with 5.86 g ethanol (Sigma Aldrich, St. Louis, MO) and mixed for 10 min under strong agitation. Then, 0.03567 g of Ν,Ν,Ν',Ν'-tetramethylethylenediamine in 5 g ethanol was added into the above solution under strong agitation and mixed for 5 minutes.

[0205] Step 4. Next, the solution from step 3 was cast on a PET liner using the procedure in Specific Example 1 and dried in air for about 20 minutes, with checking that the surface was dry and not sticky, to form a film that was about 5 μπι thick.

[0206] Step 5. Next, the resultant film was coated with PSTMIM solution prepared as in Specific Example 1. The obtained membrane was dried in a vacuum oven at 70°C as before. Then, the membrane was soaked in DI water overnight before testing.

[0207] Next, the copper and zinc crossovers and the conductivity were measured using the procedures in Specific Example 1. Results are shown in Table 2. Notice that the figure of merit is similar to that in Specific Example 1.

[0208] Other surface treatments could yield a layer with a high concentration of positively changed species.

Specific Example 16: Addition of a polymerized positively charged cyclic amine surfactant containing pyridinium

[0209] Step 1: Preparation of the surfactant. 4.9 g of 11-Bromo-l- undecene (Sigma Aldrich) was dissolved in 78.6 g of 2-propanol (Sigma Aldrich) at room temperature. 11.3 g of 4,4'-Trimethylenedipyridine (Sigma Aldrich) was dissolved in 49 g of toluene at room temperature. The two solutions were mixed and then the reactor was heated to 80°C and maintained for 19 hours.

[0210] Step 2: Purification. The reactor was cooled to room temperature, and the solvent was removed by rotovaporation, the crude product was further purified by recrystallization in ethyl acetate (Sigma Aldrich) and then dried in a vacuum oven overnight to yield a surfactant gel.

[0211] Step 3: Casting. 5 g of the resultant surfactant, 5 g of glycerol and about 0.02 g of Dimethoxy-2-phenylacetophenone were dissolved in 15 g of DOWANOL PM. About 0.5 cc of the resultant solution was spread onto the surface of the membrane prepared in specific example 1. The membrane was placed under a UV blacklight for 2 hours to polymerize the surfactant.

Specific Example 17: Addition of a polymerized positively charged cyclic amine surfactant containing piperidinium

[0212] Step 1: Preparation of the surfactant. 11.2 g of 11-Bromo-l- undecene (Sigma Aldrich) was dissolved in 300 ml of methanol(Sigma Aldrich) at room temperature. 4.77 g of 4,4'-Trimethylenedbis)l-methylpiperidine) (Sigma Aldrich) was dissolved in 10 g of methanol at room temperature. The two solutions were mixed and then the reactor was heated to 60°C and maintained for 24 hours.

[0213] Step 2: Purification. The reactor was cooled to room temperature, and the solvent was removed by rotovaporation and washed in hexane and dried in vacuum overnight at 80°C.

[0214] Step 3: Casting. 5 g of the resultant surfactant, 5 g of glycerol and about 0.02 g of Dimethoxy-2-phenylacetophenone were dissolved in 15 g of DOWANOL PM. About 0.5 cc of the resultant solution was spread onto the surface of the membrane prepared in specific example 1. The membrane was placed under a UV blacklight for 2 hours to polymerize the surfactant.

[0215] Other positively charged cyclic amine surfactants could be substituted for the positively charged cyclic amine surfactant described in this specific example, including the polymerizable ionic liquid surfactants described in US 7,931,824. In general, the polymerizable ionic liquids surfactants of the form: where:

Ri9 and R21 are bifunctional groups comprising positively charged cyclic amines;

R20 is a bifunctional group selected from linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls, having no more than 20 carbon atoms; and

R ₁₈ and R22 are monofunctional groups independently selected from linear alkyls, branched alkyls, cyclic alkyls, heteroalkyls, aryls, heteroaryls, alkylaryls, and heteroalkylaryls, wherein each of R ₁₈ and R22 contain at least one polymerizable double bond.

[0216] The '824 patent discloses surfactants where R^ and R21 comprise imidazoliums. The results here suggest that it may be preferred for R^ and R21 to be something other than an imidazolium to better control the pore size.

[0217] While the example here used the membrane in specific example 1 as a support, other ion conducting polymers could also be used. In addition, porous, microporous or nano fibrous materials could be used. Examples of porous materials useful for an alkaline battery include: ePTFE, porous

polyethylene(PE), porous polypropylene (PE), porous high-density polyethylene (HDPE), porous crosslinked polyvinyl alcohol (PVA), porous polystyrene (PS), and porous polysulfone (PSO).

[0218] The examples given above are merely illustrative and are not meant to be an exhaustive list of all possible embodiments, applications or modifications of the present electrochemical device. Thus, various modifications and variations of the described methods and systems of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. In particular, the methods to enhance the figure of merit described in Specific Examples 2 through 15 could be applied to other polymeric battery separators. Although the invention has been described in connection with specific embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention that are obvious to those skilled in the chemical arts or in the relevant fields are intended to be within the scope of the appended claims. [0219] While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.