WO2022237990A1 - Metal-air rechargeable flow battery with zn-based nanoelectrofuel and process for obtaining an air cathode for such metal-air flow battery - Google Patents

Metal-air rechargeable flow battery with zn-based nanoelectrofuel and process for obtaining an air cathode for such metal-air flow battery Download PDF

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Publication number
WO2022237990A1
WO2022237990A1 PCT/EP2021/062855 EP2021062855W WO2022237990A1 WO 2022237990 A1 WO2022237990 A1 WO 2022237990A1 EP 2021062855 W EP2021062855 W EP 2021062855W WO 2022237990 A1 WO2022237990 A1 WO 2022237990A1
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WIPO (PCT)
Prior art keywords
air
zinc
metal
flow battery
nanoelectrofuel
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PCT/EP2021/062855
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French (fr)
Inventor
Giuseppe Valsecchi
Robert David BAHHAM
Alessandra ACCOGLI
Luca BERTOLI
Gabriele PANZERI
Eugenio GIBERTINI
Matteo SALERNO
Luca Magagnin
Jeffrey Charles LYONS
Original Assignee
Media Lario S.R.L.
Politecnico Di Milano
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Application filed by Media Lario S.R.L., Politecnico Di Milano filed Critical Media Lario S.R.L.
Priority to EP22731994.4A priority Critical patent/EP4338226A1/en
Priority to PCT/EP2022/063196 priority patent/WO2022238584A1/en
Priority to KR1020237043324A priority patent/KR20240039606A/en
Priority to CN202280035130.1A priority patent/CN117678112A/en
Priority to US18/560,785 priority patent/US20240222744A1/en
Priority to JP2023570191A priority patent/JP2024518090A/en
Publication of WO2022237990A1 publication Critical patent/WO2022237990A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M12/00—Hybrid cells; Manufacture thereof
    • H01M12/08—Hybrid cells; Manufacture thereof composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M16/00—Structural combinations of different types of electrochemical generators
    • H01M16/003—Structural combinations of different types of electrochemical generators of fuel cells with other electrochemical devices, e.g. capacitors, electrolysers
    • H01M16/006—Structural combinations of different types of electrochemical generators of fuel cells with other electrochemical devices, e.g. capacitors, electrolysers of fuel cells with rechargeable batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/42—Alloys based on zinc
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8647—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites
    • H01M4/8652—Inert electrodes with catalytic activity, e.g. for fuel cells consisting of more than one material, e.g. consisting of composites as mixture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • the present invention provides a slurry-based zinc-air flow battery.
  • the overall idea of the project comprises four different aspects:
  • GPE alkaline gel polymeric electrolyte
  • CPE composite polymeric electrolyte
  • the invention includes a process for obtaining an air cathode for such metal- Air flow battery, and ultimately, the use of such a battery.
  • Metal-air batteries have always been of great interests from many points of view, at the academic and industrial level and nowadays for the growing interests in renewables and green energy sources. It is considered one of the most promising technologies for a carbon-free sustainable energy economy.
  • the electrochemical reactions involved in a Zn-air battery are: V)
  • MABs are based on very cheap active materials, like zinc, which are widely available on the market, safe and environmentally friendly. Moreover, on one side of the battery, i.e. the positive electrode, the active material is air, basically massless. For this reason, this technology can reach extremely high energy densities, practically between 350 and 1100 Wh/kg, which is higher than the current state of the art for Li-ion batteries.
  • ZAB Zinc-Air Battery
  • alkaline environment is selected for metal-air batteries because of the easier control of the metallic species, the higher voltage output and the optimal behaviour and stability of the air cathode, favouring oxygen reactions.
  • EP 0458395 A1 discloses a method of charging a zinc suspension storage battery: zinc suspension storage battery and zinc suspension to be used for a storage battery and IEEE TRANSACTION ON ULTRASONICS, FERROELECTRICS AND FREQUENCY CONTROL, of Kuosch Christian et al. , XP011840417, vol. 68, no. 3 and published on July 6th, 2020 discloses in pages 807-817 relevant information on an Ultrasound Super-Resolution Flow Measurement of Suspension in Narrow Channels.
  • Object of the invention Considering this technical background, it is the object of the present invention to provide a rechargeable battery with improved energy density, in particular up to 10-15 times the energy density of a typical Vanadium Redox Flow Battery (VRB) and up to more than 2-5 times the energy density of a Lithium-ion battery storage device.
  • This battery should provide a long lifetime of at least 10 years, with minimal maintenance and remain stable over a period up to of 5000-15000 cycles without 3 appreciable losses of the capacity.
  • This new battery should also avoid the use of rare and dangerous materials which pose a risk to the user and which are problematic for recycling.
  • a metal air flow battery comprising:
  • GPE alkaline gel polymer electrolyte
  • CPE composite polymer electrolyte
  • the alkaline gel polymer electrolyte (GPE) or an alkaline composite polymer electrolyte (CPE) forms the positive electrode having air as active material.
  • An oxygen reduction reaction (ORR) / oxygen evolution reaction (OER) catalyst material serves for an efficient air conversion.
  • ORR oxygen reduction reaction
  • OER oxygen evolution reaction
  • Membrane in WO2016/031201 A1 water permeable ion-exchange membrane (IEM), not further disclosed, while in the present battery it is a gel polymer electrolyte (GPE) based on PVA, PAA or PAM.
  • IEM water permeable ion-exchange membrane
  • GPE gel polymer electrolyte
  • Zn reservoir in WO2016/031201 A1 Two reservoirs, a slurry feed with fresh zinc and a slurry collection for spent zinc. IN contrast: Present battery comprises only one single chamber.
  • Zinc concentration in WO2016/031201 A1 15 M (size 1pm-500pm), and 30 M demonstrated.
  • Present battery contains a zinc concentration of 10 - 40% by volume which corresponds to around 10 M - 40 M.
  • the battery of WO2016/031201 A1 is constituted by a double chamber, or a piston to drive the fluid from a chamber to another.
  • present battery is using a pump and a single reservoir.
  • EP 0 458 395 A1 discloses a zinc-suspension/air storage battery. Its main characteristics are these, partly in comparison with the ones of the battery of the present invention:
  • Electrode/current collector Material with high overpotential for zinc build up so that the reaction takes place on the zinc particles.
  • material for the electrode magnesium, vanadium, niobium, boron carbide, zirconium nitride, glassy carbon, pyrolytic carbon is being used.
  • Thickeners Suitable silicates with diameters less than 1 pm and up to 5 wt.% are being used. In contrast, the present invention is using sodium alginate, xanthan gum and polyacrylic acid.
  • Zinc-suspension According to EP 0458395 A1 , 5 - 25 % by volume, while in present battery, 10 - 40 % by volume which corresponds to around 10 M - 40 M. No carbon addition is mentioned for conductivity improvement. Mentioned is, however, “a stabiliser which is chosen from ceramic materials which are optionally electrically conductive, metals and silicate compounds” - but again no carbon.
  • Membrane separator in Kuosch et al. (IEEE TRANSACTION, July 6 th , 2020): Celgard 5550, while in present battery an alkaline gel polymer electrolyte (GPE) based on PVA, PAA or PAM is being used;
  • GPE alkaline gel polymer electrolyte
  • This present technology relies on commonly available and non-toxic materials and integrates a zinc-based nanoelectrofuel and an alkaline gel polymer electrolyte (GPE) or an alkaline composite polymer electrolyte (CPE) in the electrochemical cell.
  • GPE alkaline gel polymer electrolyte
  • CPE alkaline composite polymer electrolyte
  • an aqueous-based supporting electrolyte based on hydroxides salts comprising sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, or a combination of two or more thereof, in order to provide ionic conductivity (higher than 100 mS cm 1 ) of the solution and high solubility of zinc-based salts.
  • the overall concentration of hydroxides is comprised between 0.01 M and 20 M, preferably from 0.1 M to 15 M, still more preferably from 1 M to 10 M;
  • zinc-based salt dissolved into the supporting electrolyte comprising zinc hydroxide (Zn(OH)2), acetate (Zn(CH3C00 2 )), chloride (ZnCh), acting as main source of Zn 2+ ions, in a concentration between 0.001 M to 1.5 M, preferably from 0.01 M to 1 M, still more preferably from 0.1 M to 1 M.
  • zinc-based particles such as Zn and/or ZnO particles acting as dispersed electrode and additional source of zinc on top of which electrodeposition of metallic zinc, during the charging phase of the battery, can occur.
  • concentration of zinc-based particles with an average diameter ranging from 200 nm to 100 micrometers, is comprised between 1 % to 50% by volume, preferably between 10% and 40% by volume.
  • zinc-based particles can be functionalized with organic or inorganic coatings comprising polyacrylic acid (PAA), polyethyleneimine (PEI), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), oleic acid, Nafion®, lignin, succinic acid, chitosan, oxides and metals.
  • PAA polyacrylic acid
  • PEI polyethyleneimine
  • CMC carboxymethyl cellulose
  • PVA polyvinyl alcohol
  • oleic acid Nafion®
  • lignin lignin
  • succinic acid chitosan
  • oxides and metals oxides and metals.
  • different additives are introduced in the solution comprising silicates, Pb, Bi, Sn, In, oxides and boric acid and dextrins in order to act as H2 suppressing agents and leveling agents to reduce dendrites growth during electrodeposition.
  • thickeners compounds, 8 added to stabilize zinc-based particles’ dispersion in the electrolyte are dissolved in the previously shown formulation.
  • the group of thickener compounds can comprise sodium alginate, xanthan gum and polyacrylic acid (PAA), added to the nanoeletrofuel in an amount comprised between 0.1 wt.% and 5 wt.%, preferably between 0.5 wt.% and 3 wt.%.
  • high active area carbon-based compounds (of the order of 20-1000 m 2 g _1 ), comprising carbon black, graphene, expanded graphite, reduced graphene oxide, active carbon, acetylene black, carbon nanotubes and a combination or two or more thereof, are introduced in order to form a percolated slurry with high electronic conductivity of 10-100 mS cm -1
  • concentration of carbon particles is comprised between 0.1 wt.% and 10 wt.%.
  • the alkaline gel polymer electrolyte is based on polyvinyl alcohol (PVA), polyacrylic acid (PAA) or polyacrylamide (PAM) or combination of them, swelled in or containing an alkaline solution based on hydroxide salts as previously described for the supporting electrolyte (i).
  • the polymeric compounds are dissolved in a water-based solution in a concentration ranging from 0.1 wt.% to 50 wt.%, preferably from 1 wt.% to 40 wt.%, still more preferably from 5 wt.% to 30 wt.%.
  • the GPE can be modifying adding organic/inorganic reinforcing particles with different aspect ratio (e.g. rod, wire, fiber, dot) comprising glass fibers, oxides, fluorine-based polymeric particles, MOFs, carbides, obtaining a composite polymer electrolyte (CPE).
  • organic/inorganic reinforcing particles with different aspect ratio e.g. rod, wire, fiber, dot
  • CPE composite polymer electrolyte
  • the CPE is based on (i) polyvinyl alcohol (PVA), polyacrylic acid (PAA) or polyacrylamide (PAM) or combination of them, dissolved in a water-based solution in a concentration ranging from 0.1 wt.% to 50 wt.%, preferably from 1 wt.% to 40 wt.%, still more preferably from 5 wt.% to 30 wt.% and (ii) reinforcing particles ranging from 0.1 wt.% to 10 wt.%, preferably from 0.5 wt.% to 5 wt.%.
  • PVA polyvinyl alcohol
  • PAA polyacrylic acid
  • PAM polyacrylamide
  • Figure 1 shows the flow battery of the present invention in a schematic representation
  • Figure 2 shows a single cell flow battery in squared configuration
  • Figure 3 shows a single cell flow battery in squared configuration during operation.
  • the described zinc-based nanoelectrofuel 2 is contained in a single tank 1 and is fluxed by means of a pump 11 in and out of the electrochemical cell 3.
  • the electrochemical cell is constituted by a metallic current collector 5 and a zinc-based electrode 4 at the negative side.
  • a GPE/CPE 6, a nickel net with ORR/OER catalytic materials on top 7, and a hydrophobic layer 8 at the positive side are all contained in an external framework 10.
  • Figure 2 shows a single cell flow battery in squared configuration showing the nickel mesh electrode with catalyst 7, the Zn electrode 4 and the external framework 10. The screws 12 keep the parts together and avoid a leaking of the nanoelectrofuel.
  • the GPE/CPE component is not visible being inside the electrochemical cell.
  • Figure 3 shows such a single cell flow battery in squared configuration during operation.
  • the Zn-based nanoelectrofuel 2 is contained in the external reservoir 1 and is being pumped in and out the battery cell of this Zinc Air Battery 10
  • Aspect 1 The zinc-based nanoelectrofuel
  • the zinc-based electrolyte of the invention acts as the anolyte, i.e. a reduction reaction occurs during charging and an oxidation reaction during discharging.
  • This electrolyte contains Zn/Zn 2+ ions coming from different sources, hydroxide salts dissolved in it acting as supporting electrolyte and to guarantee alkaline environment, and different additives to improve the performance of the battery.
  • the Zn/Zn 2+ source does not come exclusively from zinc compounds like the traditional employed ZnO typically used in common alkaline Zn-based flow battery, such as in EP 0458395 A1 and by Kuosch et al. (IEEE transaction, July, 6 th 2020).
  • the particle-laden flow is further implemented with the addition of high active area carbon particles in order to create a percolated network, substantially increasing the active area for the reaction to occur, guaranteeing higher current densities and consequently improved power rate of the present Zinc Air flow Battery (ZAB).
  • ZAB Zinc Air flow Battery
  • Different additives are introduced in the solution, mainly hydrogen suppressing agents and levelling agents to increase the coulombic efficiency of the device and smooth the zinc deposit against dendrites, respectively.
  • thickeners additive are introduced, avoiding the particles precipitation and obtaining a viscoelastic fluid.
  • the properly selected zinc salts, added to the zinc-based nanoelectrofuel allow to obtain a synergic effect during the charging process due to the presence of a controlled environment, rich of zinc ions around the particles, fostering the electrochemical reaction.
  • Aspect 2 The Oxygen Reduction Reaction (ORR)/ Oxygen Evolution Reaction (OER) catalyst material
  • the air cathode is obtained through sequential steps.
  • the current collector material is a nickel net or it can be a hydrophobic carbon paper/cloth onto which the catalytic materials are deposited.
  • An electrochemical etching treatment is previously done on the nickel net to increase its geometrical surface area, followed by a bubble templating treatment to increase its geometrical surface area.
  • the latter is performed in a nickel bath at high current densities comprised between 0.1 and 10 A cm -2 , more preferably between 0.5 and 2 A cm -2 for a duration ranging between 10 seconds and 10 minutes.
  • the nickel bath contains nickel salts comprising nickel chloride (N1CI2), sulfate (N1SO4), sulfamate (Ni(S03NH2)2), nitrate (Ni(N03)2) or a combination of those, in a concentration comprised between 0.05 M and 1 M, more preferably between 0.1 M and 0.5 M.
  • the catalytic materials are then electrodeposited in two steps: a first manganese oxide (MnO x ) layer, to catalyze the Oxygen Reduction Reaction (ORR); finally, the layer of mixed transition metal oxides (e.g. Ni, Fe, Co), hydroxides or oxyhydroxides on top to catalyze the Oxygen Evolution Reaction (OER).
  • the catalytic materials can be deposited applying anodic or cathodic current densities ranging from 1 to 100 mA cm -2 , preferably from 10 to 50 mA cm -2 for a range of time comprised between 1 minute to 60 minutes, preferably from 10 minutes to 30 minutes.
  • post- treatment of the as synthesizing materials can be applied, such as, acidic digestion, chemical, thermal, or thermochemical treatments in order to control the final crystallinity of the catalysts.
  • a final heat treatment is employed to improve the crystallinity and the stabilization of catalysts at temperature comprised between 300 °C and 500 °C in controlled atmosphere or in air for a time ranging between 30 minutes to 6 hours, preferably between 1 hour to 4 hours.
  • the morphology of the deposit highly influences the performances and the stability of the electrode and therefore the deposition conditions and the bath composition has been carefully selected for the optimal result.
  • a hydrophobic layer is applied on top of the catalytic materials by any suitable deposition techniques such as spraying, dip coating, spin coating.
  • the hydrophobic layer is based on polymeric materials, comprising polytetrafluoroethylene (PTFE), ionomers, including perfluorosulfonic acids (PFSAs) (e.g. sulfonated tetrafluoroethylene (Nafion®), Aquivion®, Fumasep®), hydrocarbons sulfonated poly(phenylene sulfone)s (e.g sulfonated polyether ether ketone (sPEEK), 12 sulfonated polystyrene (PSS)), poly(acrylic acid) (PAA), Surlyn® or a combination of two or more thereof.
  • PFSAs perfluorosulfonic acids
  • sPEEK sulfonated polyether ether ketone
  • PSS poly(acrylic acid)
  • PAA poly(acrylic acid)
  • Surlyn® Surlyn® or a combination of two or more thereof.
  • This additional layer can further improve
  • a Zinc Air flow Battery (ZAB) with a flowing electrolyte can, as previously said, overcome two of the issues regarding the use of zinc as active material for the anode.
  • the dendrites growth is reduced due to the continuous movement of the flowing electrolyte and furthermore the possibility for the zinc hydroxides, formed during discharge, to accumulate and precipitate as a passive ZnO layer, is greatly reduced.
  • the innovative flow field is developed to properly suit the behavior of the viscoelastic particle laden fluid; at the same time the main focus is to allow the smooth flow of the viscoelastic slurry, without introducing losses and avoiding accumulation of particles in dead areas inside the cell.
  • the cell of the present invention has a versatile, depending on the size of the tank. Air comes from the external surface while the zinc electrode is placed on the other side, in between the two the nanoelectrofuel is pumped in and out.
  • a gel polymer electrolyte (GPE) based on PVA, PAA or PAM protects the air cathode from zinc ions contamination guaranteeing at the same time an efficient ionic exchange and allows the assembly of a single-cell flow ZAB, different from the state-of-the-art double electrolytes metal-air flow cells, such as the one proposed by Kisdarjono et al. in WO 2016/031201.
  • the specifications of the present invention can be selected at need depending on the application due to the great flexibility of the flow battery system, from kW/kWh to MW/MWh range by increasing the size of the nanoelectrofuel tank. Indeed, the advantages of the adoption of a flow technology are above all the decoupling of power and energy, and the easy scalability of the system. A long lifetime of at least 10 years is guaranteed with minimal maintenance in that period and a stability of 5000-15000 cycles is expected without appreciable losses of capacity. 13
  • Such a rechargeable battery has many applications. For example, it can be used for the propulsion of vehicles on land, on water, in the air. More particularly, it can be used for the powering of consumer electronics, power tools, measuring instruments vehicles, the propulsion of partly or fully electrically powered bicycles, motorcycles, cars, trucks, baggers, cranes on land, partly or fully electrically powered boats, ships, submarines on or in water, partly or fully electrically powered aircraft such as helicopters, ultralight planes, microlight planes, ecolight planes, single and multiengine planes, fighters, transportation planes, airliners, hot air and gas balloons and airships in the air, space application, as permanent rechargeable power sources for houses and industrial sites, military applications, power systems of all sorts.
  • partly or fully electrically powered bicycles such as helicopters, ultralight planes, microlight planes, ecolight planes, single and multiengine planes, fighters, transportation planes, airliners, hot air and gas balloons and airships in the air, space application, as permanent rechargeable power sources for

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Abstract

This Metal-Air flow battery with Zn-based nanoelectrofuel comprises an alkaline Zinc half-cell containing a zinc-based nanoelectrofuel half-cell (1), with particles dispersed in the nanoelectrofuel. The positive electrode has air as active material, and an ORR/OER catalyst material is being used for efficient air conversion. The Metal-Air flow battery does preferably comprise a zinc-based electrolyte (2) as the anolyte, so a reduction reaction occurs during charging and an oxidation reaction during discharging. This electrolyte contains Zn/Zn2+ ions, coming from different sources, hydroxide salts to have an alkaline environment, and an electrolyte with suspended metallic with at least zinc and/or ZnO particles in a concentration as high as 10-40% by volume in it, as the source of active material. This is being used in instead of only ZnO, Zn acetate as traditional electrolyte of a ZAB, in order to approaching the high theoretical values of the common zinc-air technology so the nanoelectrofuel does behave as a viscoelastic fluid.

Description

1
Media Lario s.r.l., Localita Pascolo, 1-23842 Bosisio Parini (LC), Italy and
Poltecnico di Milano, Piazza Leonardo da Vinci, 32, 1-20133 Milano, Italy
Metal-Air rechargeable flow battery with Zn-based nanoelectrofuel and process for obtaining an air cathode for such metal-Air flow battery
[0001] The present invention provides a slurry-based zinc-air flow battery. The overall idea of the project comprises four different aspects:
1 . an alkaline zinc half-cell containing a zinc-based nanoelectrofuel as active material;
2. an alkaline gel polymeric electrolyte (GPE) or a composite polymeric electrolyte (CPE) integrated into the electrochemical cell;
3. a process for the synthesis of oxygen reduction reaction (ORR )/ oxygen evolution reaction (OER) catalytic materials;
4. a rechargeable flow battery with original assembly and design.
Furthermore, the invention includes a process for obtaining an air cathode for such metal- Air flow battery, and ultimately, the use of such a battery.
[0002] Metal-air batteries (MABs) have always been of great interests from many points of view, at the academic and industrial level and nowadays for the growing interests in renewables and green energy sources. It is considered one of the most promising technologies for a carbon-free sustainable energy economy. The electrochemical reactions involved in a Zn-air battery are: V)
Figure imgf000003_0001
In summary, an overall theoretical open circuit voltage (OCV) of 1.59 V is obtained. 2
[0003] MABs are based on very cheap active materials, like zinc, which are widely available on the market, safe and environmentally friendly. Moreover, on one side of the battery, i.e. the positive electrode, the active material is air, basically massless. For this reason, this technology can reach extremely high energy densities, practically between 350 and 1100 Wh/kg, which is higher than the current state of the art for Li-ion batteries.
[0004] One of the historical limitations for a rechargeable battery based on zinc is to have a reversible zinc redox reaction, especially in an alkaline environment. This is due to the ease of passivation of the zinc surface by a layer of insulating ZnO during the discharge phase, and to the ease of dendritic growth of zinc during the charge phase. The Zinc-Air Battery (ZAB) proposed herein with an integrated flow technology allows to reduce both these issues and thereby paving the way to the implementation of a ZAB with a very high cyclability and operational life.
[0005] Usually, alkaline environment is selected for metal-air batteries because of the easier control of the metallic species, the higher voltage output and the optimal behaviour and stability of the air cathode, favouring oxygen reactions.
[0006] In the state of the art, the document WO2016/031201 A1 does disclose an air cathode battery using zinc slurry anode with carbon additives. EP 0458395 A1 discloses a method of charging a zinc suspension storage battery: zinc suspension storage battery and zinc suspension to be used for a storage battery and IEEE TRANSACTION ON ULTRASONICS, FERROELECTRICS AND FREQUENCY CONTROL, of Kuosch Christian et al. , XP011840417, vol. 68, no. 3 and published on July 6th, 2020 discloses in pages 807-817 relevant information on an Ultrasound Super-Resolution Flow Measurement of Suspension in Narrow Channels.
[0007] Object of the invention. Considering this technical background, it is the object of the present invention to provide a rechargeable battery with improved energy density, in particular up to 10-15 times the energy density of a typical Vanadium Redox Flow Battery (VRB) and up to more than 2-5 times the energy density of a Lithium-ion battery storage device. This battery should provide a long lifetime of at least 10 years, with minimal maintenance and remain stable over a period up to of 5000-15000 cycles without 3 appreciable losses of the capacity. This new battery should also avoid the use of rare and dangerous materials which pose a risk to the user and which are problematic for recycling.
[0008] Solution according to the invention. This above object is attained by a metal air flow battery, comprising:
• an alkaline electrolyte containing a zinc-based nanoelectrofuel,
• an alkaline gel polymer electrolyte (GPE) or composite polymer electrolyte (CPE),
• an air cathode with Oxygen Evolution Reaction (OER )/ Oxygen Reduction Reaction (ORR) catalytic materials, and
• a hydrophobic layer.
In the zinc-based nanoelectrofuel, particles are dispersed. The alkaline gel polymer electrolyte (GPE) or an alkaline composite polymer electrolyte (CPE) forms the positive electrode having air as active material. An oxygen reduction reaction (ORR) / oxygen evolution reaction (OER) catalyst material serves for an efficient air conversion. The process for obtaining an air cathode for such metal-air flow battery is characterizing steps of claim 9, and the use of the battery is characterized by claims 10 and 11.
[0009] The use of zinc-based nanoeletrofuel in the flow battery of the present invention allows to obtain surprisingly high energy density device, between 350 and 1100 Wh/kg. Furthermore, with respect to the classical microporous separators typically employed in the state of the art, e.g. in patent EP 0458395 A1 and by Kuosch et al. (IEEE transaction, July 6th, 2020, the use of the properly developed GPE/CPE guarantees
(i) an intimate contact with the catalytic materials,
(ii) the fast and selective transport of hydroxyl ions, and
(iii) the hindering of both zinc particles and zincate ions through the air electrode, inducing damaging of the catalytic materials and short circuits of the device, thus reducing the flow battery lifetime.
[0010] Moreover, the integration of the developed alkaline GPE/CPE guarantees a continuous availability of OH- ionic species at the air cathode, therefore the need of additional external water reservoir, as described for example in WO 2016/031201 , falls. When comparing the present rechargeable battery with the one disclosed in this state-of- the-art documents, the following important distinctions need to be mentioned and considered: 4
• Catalyst in Pt/C on carbon paper, while in the present battery it is MnOx for ORR and transition metal oxide for OER on Nickel net.
• Membrane in WO2016/031201 A1: water permeable ion-exchange membrane (IEM), not further disclosed, while in the present battery it is a gel polymer electrolyte (GPE) based on PVA, PAA or PAM.
• Complexing agents in WO2016/031201 A1: Taken from a group consisting of ethylene diamine tetra acetic acid (EDTA), citric acid, and ammonium hydroxide. In contrast, in the present battery sodium alginate, xanthan gum and polyacrylic acid are being used as thickeners.
• Zn reservoir in WO2016/031201 A1 : Two reservoirs, a slurry feed with fresh zinc and a slurry collection for spent zinc. IN contrast: Present battery comprises only one single chamber.
• Zinc concentration in WO2016/031201 A1: 15 M (size 1pm-500pm), and 30 M demonstrated. Present battery contains a zinc concentration of 10 - 40% by volume which corresponds to around 10 M - 40 M.
• Carbon additives in WO2016/031201 A1: 2.5-10 wt.%. Present battery works with a percentage comprised between 0.1 wt.% and 10 wt.%.
• The battery of WO2016/031201 A1 is constituted by a double chamber, or a piston to drive the fluid from a chamber to another. In contrast, present battery is using a pump and a single reservoir.
• Use of the GDL in WO2016/031201 A1 : substrate to deposit the catalyst onto, let air in and avoid electrolyte out.
• In WO2016/031201 A1 it says: “Such a slurry demonstrated a Coulombic efficiency as high as 95%, utilization of 63% with a capacity retention of 95% over 10 cycles, at current density of 30 milliamperes per square centimetres (mA/cm)”. But data for supporting this statement is missing.
[0011] No zinc salts are present in the formulation of the nanoelectrofuel according to WO201 6/031201 A1, so the dissolution of zinc particles would be uncontrolled, preventing an efficient rechargeability. No considerations are presented in WO201 6/031201 A1 on how to recharge the spent zinc-based fuel. This is probably due to the use of the proposed complexing agents (e.g. citric acid and EDTA) that help in the stabilization of the zinc fluid but prevents the Zn ions to be efficiently recharged. For practical applications, this system is not suitable for automotive and/or portable devices 5 because the presence of two tanks and the complex and delicate architecture, as disclosed in Fig. 1 A and Fig. 5 makes it inappropriate for such application. The present battery with only one reservoir is more compact and therefore suitable for vehicle propulsion.
[0012] EP 0 458 395 A1 discloses a zinc-suspension/air storage battery. Its main characteristics are these, partly in comparison with the ones of the battery of the present invention:
• Electrode/current collector: Material with high overpotential for zinc build up so that the reaction takes place on the zinc particles. As material for the electrode, magnesium, vanadium, niobium, boron carbide, zirconium nitride, glassy carbon, pyrolytic carbon is being used.
• Thickeners: Suitable silicates with diameters less than 1 pm and up to 5 wt.% are being used. In contrast, the present invention is using sodium alginate, xanthan gum and polyacrylic acid.
• Zinc-suspension: According to EP 0458395 A1 , 5 - 25 % by volume, while in present battery, 10 - 40 % by volume which corresponds to around 10 M - 40 M. No carbon addition is mentioned for conductivity improvement. Mentioned is, however, “a stabiliser which is chosen from ceramic materials which are optionally electrically conductive, metals and silicate compounds” - but again no carbon.
• Catalyst in EP 0458395 A1 : Silver or platinum for OER, N1C02O4 for ORR.
• Separator in EP 0 458 395 A1: “Membrane or microporous material”. Only Fig. 3 discloses a flow battery, not in a single cell but in stack configuration. The other figures do not represent a flow battery at all. The need of an electrolyte on the cathode side is not considered. This will prevent the efficient contact between the cathode and the separator, limiting the operation of the device especially for the lack of water necessary for the oxygen reduction reaction. Considering the redox reactions reported in EP 0458395 A1 at page 2, without the presence of water on the cathode, an oxygen reduction reaction cannot occur. If, on the other hand, water thus pass through the separator, nothing will prevent the zinc ions to reach the cathode ruining the cathodic reaction.
• No GDL is present but an “impermeable partition” is employed in Fig.3, separating the cathode from the anode of the adjacent cell. 6
• How the stack in Fig.3 is closed is not disclose, but oxygen gas must be fluxed into the cathode side for the reactions to occur thus an additional system to control the gas flux is expected, on the contrary to the present invention.
[0013] Kuosch et al. (IEEE TRANSACTION, July 6th, 2020), published on July 6th, 2020 and thus after priority date of the present application, does reveal a zinc particles suspension redox flow modeling. Although this document cannot be considered a prior art for the inventors, the main characteristics in the following section has been highlighted, in a comparison with the battery disclosed in the present invention:
• Membrane separator in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020): Celgard 5550, while in present battery an alkaline gel polymer electrolyte (GPE) based on PVA, PAA or PAM is being used;
• Current collector in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020): Copper foil;
• Catalyst in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020): Commercially available Gaskatel MOC (= manganese mixed oxide). In contrast, present battery is using MnOx for ORR and a transition metal oxide for OER on a Nickel net.
Important notice: This system proposed in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020) was not electrochemically tested by any means, and if an expert in the field would integrate it into the present battery concept, some limitations will be encountered regarding the operation and efficiency. Even if considered that the air cathode is bifunctional, a catalyst constituted by only manganese oxide is suitable for the oxygen reduction reaction (ORR) but not for the oxygen evolution reaction (OER), and this will substantially reduce the energy efficiency of the battery and its cyclability. Moreover, the use of a porous separator like the one proposed in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020) cannot sustain a prolonged flow condition of this kind of fluid. Furthermore, the pressure developing inside the chamber of a flow device will push the zinc particles through the pores of the separator to the cathode, thus shortening the life cycle of the battery. Finally, a fluid on the cathode side, necessary to guarantee the redox reactions of oxygen, is not present in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020), and without a proper hydrophobic material like the PTFE-treated carbon paper used in the battery of the present invention, any water produced or permeates through the porous separator cannot be contained inside the device, causing leakages. Therefore, the system proposed in Kuosch et al. (IEEE TRANSACTION, July 6th, 2020), even combined 7 with the teaching of WO2016/031201 A1 and/or EP 0 458 395 A1 will not provide a concept for a real case scenario. The use of carbon particles to enhance the conductivity of the zinc suspension, a key feature of the battery of the present invention, is neither even considered in any of the documents WO2016/031201 A1 , EP 0458395 A1 , Kuosch et al. (IEEE TRANSACTION, July 6th, 2020) and is not mentioned anywhere.
[0014] This present technology relies on commonly available and non-toxic materials and integrates a zinc-based nanoelectrofuel and an alkaline gel polymer electrolyte (GPE) or an alkaline composite polymer electrolyte (CPE) in the electrochemical cell. The zinc- based nanoelectrofuels described in the present invention contains:
(i) an aqueous-based supporting electrolyte based on hydroxides salts comprising sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, or a combination of two or more thereof, in order to provide ionic conductivity (higher than 100 mS cm 1) of the solution and high solubility of zinc-based salts. In a preferred embodiment of the invention, the overall concentration of hydroxides is comprised between 0.01 M and 20 M, preferably from 0.1 M to 15 M, still more preferably from 1 M to 10 M;
(ii) zinc-based salt dissolved into the supporting electrolyte comprising zinc hydroxide (Zn(OH)2), acetate (Zn(CH3C002)), chloride (ZnCh), acting as main source of Zn2+ ions, in a concentration between 0.001 M to 1.5 M, preferably from 0.01 M to 1 M, still more preferably from 0.1 M to 1 M.
(iii) zinc-based particles such as Zn and/or ZnO particles acting as dispersed electrode and additional source of zinc on top of which electrodeposition of metallic zinc, during the charging phase of the battery, can occur. In a preferred embodiment of the invention, the concentration of zinc-based particles, with an average diameter ranging from 200 nm to 100 micrometers, is comprised between 1 % to 50% by volume, preferably between 10% and 40% by volume. In another embodiment of the invention, zinc-based particles can be functionalized with organic or inorganic coatings comprising polyacrylic acid (PAA), polyethyleneimine (PEI), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), oleic acid, Nafion®, lignin, succinic acid, chitosan, oxides and metals.
[0015] In another embodiment of the invention, different additives are introduced in the solution comprising silicates, Pb, Bi, Sn, In, oxides and boric acid and dextrins in order to act as H2 suppressing agents and leveling agents to reduce dendrites growth during electrodeposition. In still another embodiment of the invention, thickeners compounds, 8 added to stabilize zinc-based particles’ dispersion in the electrolyte, are dissolved in the previously shown formulation. The group of thickener compounds can comprise sodium alginate, xanthan gum and polyacrylic acid (PAA), added to the nanoeletrofuel in an amount comprised between 0.1 wt.% and 5 wt.%, preferably between 0.5 wt.% and 3 wt.%.
[0016] In yet another embodiment of the invention, to the previously described formulation of the zinc-based nanoeletrofuel, high active area carbon-based compounds (of the order of 20-1000 m2 g_1), comprising carbon black, graphene, expanded graphite, reduced graphene oxide, active carbon, acetylene black, carbon nanotubes and a combination or two or more thereof, are introduced in order to form a percolated slurry with high electronic conductivity of 10-100 mS cm-1 The concentration of carbon particles is comprised between 0.1 wt.% and 10 wt.%.
[0017] The alkaline gel polymer electrolyte (GPE) is based on polyvinyl alcohol (PVA), polyacrylic acid (PAA) or polyacrylamide (PAM) or combination of them, swelled in or containing an alkaline solution based on hydroxide salts as previously described for the supporting electrolyte (i). In a preferred embodiment of the invention, the polymeric compounds are dissolved in a water-based solution in a concentration ranging from 0.1 wt.% to 50 wt.%, preferably from 1 wt.% to 40 wt.%, still more preferably from 5 wt.% to 30 wt.%.
[0018] In another embodiment of the invention, the GPE can be modifying adding organic/inorganic reinforcing particles with different aspect ratio (e.g. rod, wire, fiber, dot) comprising glass fibers, oxides, fluorine-based polymeric particles, MOFs, carbides, obtaining a composite polymer electrolyte (CPE). In a preferred embodiment of the invention, the CPE is based on (i) polyvinyl alcohol (PVA), polyacrylic acid (PAA) or polyacrylamide (PAM) or combination of them, dissolved in a water-based solution in a concentration ranging from 0.1 wt.% to 50 wt.%, preferably from 1 wt.% to 40 wt.%, still more preferably from 5 wt.% to 30 wt.% and (ii) reinforcing particles ranging from 0.1 wt.% to 10 wt.%, preferably from 0.5 wt.% to 5 wt.%.
[0019] The technology as so far developed allows to eliminate the usual second electrolyte tank of traditional flow batteries relying on ambient air as unlimited source of 9 active materials. Also eliminated is an expensive membrane material, substituted by the GPE or CPE increasing flow battery performances and cycle life. Moreover, the use of a single tank, containing both the charged and discharged zinc species of the nanoelectrofuel, allows a continuous charge and discharge of the nanoelectrofuels and it simplifies the overall operation of the device. This differentiates the architecture of the present invention from similar systems already available in the state of the art, such as e.g. WO 2016/031201 in which two reservoirs are employed, one containing the fresh active material while the other one collecting the spent electrolyte. The result is a much easier and inexpensive system with one single tank, no need for synchronizing more than one flow pump and straightforward assembly.
[0020] The design of this battery will be described in the following by way of examples and is illustrated in the figures.
Figure 1 : shows the flow battery of the present invention in a schematic representation;
Figure 2 : shows a single cell flow battery in squared configuration;
Figure 3 : shows a single cell flow battery in squared configuration during operation.
[0021] As can be seen in Figure 1, the described zinc-based nanoelectrofuel 2 is contained in a single tank 1 and is fluxed by means of a pump 11 in and out of the electrochemical cell 3. The electrochemical cell is constituted by a metallic current collector 5 and a zinc-based electrode 4 at the negative side. A GPE/CPE 6, a nickel net with ORR/OER catalytic materials on top 7, and a hydrophobic layer 8 at the positive side are all contained in an external framework 10. Figure 2 shows a single cell flow battery in squared configuration showing the nickel mesh electrode with catalyst 7, the Zn electrode 4 and the external framework 10. The screws 12 keep the parts together and avoid a leaking of the nanoelectrofuel. The GPE/CPE component is not visible being inside the electrochemical cell. Figure 3 shows such a single cell flow battery in squared configuration during operation. The Zn-based nanoelectrofuel 2 is contained in the external reservoir 1 and is being pumped in and out the battery cell of this Zinc Air Battery 10
(ZAB). The pump 11 is not shown. In the following, various important aspects of this concept are being discussed in more detail:
[0022] Aspect 1: The zinc-based nanoelectrofuel
The zinc-based electrolyte of the invention acts as the anolyte, i.e. a reduction reaction occurs during charging and an oxidation reaction during discharging. This electrolyte contains Zn/Zn2+ ions coming from different sources, hydroxide salts dissolved in it acting as supporting electrolyte and to guarantee alkaline environment, and different additives to improve the performance of the battery. In the present invention, the Zn/Zn2+ source does not come exclusively from zinc compounds like the traditional employed ZnO typically used in common alkaline Zn-based flow battery, such as in EP 0458395 A1 and by Kuosch et al. (IEEE transaction, July, 6th 2020). This approach is indeed quite limiting in terms of energy density because of the low solubility of this compound in the alkaline environment, ca. 0.5 M in saturated KOH solution. Indeed, by properly selecting alternative salts such as zinc acetate or chloride as previously described, resulting in a substantially increased Zn/Zn2+ availability, and suspending metallic zinc and/or ZnO particles into the electrolyte, at a concentration as high as 10 - 40% by volume, it is possible to overcome the limited concentration of active material approaching the high theoretical values of the zinc-air technology. The particles, dispersed in the nanoelectrofuel can have different morphologies and diameters and different functionalization coatings to promote the suspension stability and the electrochemical activity in the alkaline media. The particle-laden flow is further implemented with the addition of high active area carbon particles in order to create a percolated network, substantially increasing the active area for the reaction to occur, guaranteeing higher current densities and consequently improved power rate of the present Zinc Air flow Battery (ZAB). Different additives are introduced in the solution, mainly hydrogen suppressing agents and levelling agents to increase the coulombic efficiency of the device and smooth the zinc deposit against dendrites, respectively. Moreover, in order to control the electrolyte’s viscosity and to improve nanoelectrofuel stability, thickeners additive are introduced, avoiding the particles precipitation and obtaining a viscoelastic fluid. With respect to WO 2016/031201 , the properly selected zinc salts, added to the zinc-based nanoelectrofuel, allow to obtain a synergic effect during the charging process due to the presence of a controlled environment, rich of zinc ions around the particles, fostering the electrochemical reaction. 11
[0023] Aspect 2: The Oxygen Reduction Reaction (ORR)/ Oxygen Evolution Reaction (OER) catalyst material
The air cathode is obtained through sequential steps. The current collector material is a nickel net or it can be a hydrophobic carbon paper/cloth onto which the catalytic materials are deposited. An electrochemical etching treatment is previously done on the nickel net to increase its geometrical surface area, followed by a bubble templating treatment to increase its geometrical surface area. The latter is performed in a nickel bath at high current densities comprised between 0.1 and 10 A cm-2, more preferably between 0.5 and 2 A cm-2 for a duration ranging between 10 seconds and 10 minutes. The nickel bath contains nickel salts comprising nickel chloride (N1CI2), sulfate (N1SO4), sulfamate (Ni(S03NH2)2), nitrate (Ni(N03)2) or a combination of those, in a concentration comprised between 0.05 M and 1 M, more preferably between 0.1 M and 0.5 M. The catalytic materials are then electrodeposited in two steps: a first manganese oxide (MnOx) layer, to catalyze the Oxygen Reduction Reaction (ORR); finally, the layer of mixed transition metal oxides (e.g. Ni, Fe, Co), hydroxides or oxyhydroxides on top to catalyze the Oxygen Evolution Reaction (OER). The catalytic materials can be deposited applying anodic or cathodic current densities ranging from 1 to 100 mA cm-2, preferably from 10 to 50 mA cm-2 for a range of time comprised between 1 minute to 60 minutes, preferably from 10 minutes to 30 minutes. In a further embodiment of the invention, post- treatment of the as synthesizing materials can be applied, such as, acidic digestion, chemical, thermal, or thermochemical treatments in order to control the final crystallinity of the catalysts. As further preferred embodiment, a final heat treatment is employed to improve the crystallinity and the stabilization of catalysts at temperature comprised between 300 °C and 500 °C in controlled atmosphere or in air for a time ranging between 30 minutes to 6 hours, preferably between 1 hour to 4 hours. The morphology of the deposit highly influences the performances and the stability of the electrode and therefore the deposition conditions and the bath composition has been carefully selected for the optimal result. As a further embodiment of the invention, a hydrophobic layer is applied on top of the catalytic materials by any suitable deposition techniques such as spraying, dip coating, spin coating. The hydrophobic layer is based on polymeric materials, comprising polytetrafluoroethylene (PTFE), ionomers, including perfluorosulfonic acids (PFSAs) (e.g. sulfonated tetrafluoroethylene (Nafion®), Aquivion®, Fumasep®), hydrocarbons sulfonated poly(phenylene sulfone)s (e.g sulfonated polyether ether ketone (sPEEK), 12 sulfonated polystyrene (PSS)), poly(acrylic acid) (PAA), Surlyn® or a combination of two or more thereof. This additional layer can further improve the protection and stability of the catalyst, keeping unchanged its wettability toward the alkaline GPE/CPE and the ion exchange.
[0024] Aspect 3: Flow battery assembly and design
A Zinc Air flow Battery (ZAB) with a flowing electrolyte can, as previously said, overcome two of the issues regarding the use of zinc as active material for the anode. On one side the dendrites growth is reduced due to the continuous movement of the flowing electrolyte and furthermore the possibility for the zinc hydroxides, formed during discharge, to accumulate and precipitate as a passive ZnO layer, is greatly reduced. Moreover, the innovative flow field is developed to properly suit the behavior of the viscoelastic particle laden fluid; at the same time the main focus is to allow the smooth flow of the viscoelastic slurry, without introducing losses and avoiding accumulation of particles in dead areas inside the cell. Therefore, a traditional microchannel design cannot be used here due to the presence of the particles and to the viscosity of the solution, so a different approach is introduced. The cell of the present invention has a versatile, depending on the size of the tank. Air comes from the external surface while the zinc electrode is placed on the other side, in between the two the nanoelectrofuel is pumped in and out. A gel polymer electrolyte (GPE) based on PVA, PAA or PAM protects the air cathode from zinc ions contamination guaranteeing at the same time an efficient ionic exchange and allows the assembly of a single-cell flow ZAB, different from the state-of-the-art double electrolytes metal-air flow cells, such as the one proposed by Kisdarjono et al. in WO 2016/031201.
[0025] Performance and Upscale:
The specifications of the present invention can be selected at need depending on the application due to the great flexibility of the flow battery system, from kW/kWh to MW/MWh range by increasing the size of the nanoelectrofuel tank. Indeed, the advantages of the adoption of a flow technology are above all the decoupling of power and energy, and the easy scalability of the system. A long lifetime of at least 10 years is guaranteed with minimal maintenance in that period and a stability of 5000-15000 cycles is expected without appreciable losses of capacity. 13
[0026] Such a rechargeable battery has many applications. For example, it can be used for the propulsion of vehicles on land, on water, in the air. More particularly, it can be used for the powering of consumer electronics, power tools, measuring instruments vehicles, the propulsion of partly or fully electrically powered bicycles, motorcycles, cars, trucks, baggers, cranes on land, partly or fully electrically powered boats, ships, submarines on or in water, partly or fully electrically powered aircraft such as helicopters, ultralight planes, microlight planes, ecolight planes, single and multiengine planes, fighters, transportation planes, airliners, hot air and gas balloons and airships in the air, space application, as permanent rechargeable power sources for houses and industrial sites, military applications, power systems of all sorts.

Claims

14
Patent Claims Metal-air flow battery, comprising:
• an alkaline electrolyte containing a zinc-based nanoelectrofuel (1 ),
• an alkaline gel polymer electrolyte (GPE) or composite polymer electrolyte (CPE),
• an air cathode with Oxygen Evolution Reaction (OER )/ Oxygen Reduction Reaction (ORR) catalytic materials, and
• a hydrophobic layer. Metal-air flow battery according to claim 1 , comprising a zinc-based nanoelectrofuel (2) as the anolyte, so a reduction reaction occurs during charging and an oxidation reaction during discharging, whereby this electrolyte containing Zn/Zn2+ ions, coming from zinc hydroxide (Zn(OH)2), acetate (Zn(CH3C002)), chloride (ZnCh), hydroxide salts comprising sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide and suspended metallic particles with at least zinc and/or ZnO in a concentration as high as 10-40% by volume. Metal-air flow battery according to one of the preceding claims, in which the particles constituting a nanoelectrofuel have different morphologies and diameters ranging from hundreds of 200-800 nanometers to 1-50 micrometers and are furthermore functionalized with organic coatings comprising polyacrylic acid (PAA), polyethyleneimine (PEI), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), oleic acid, sulfonated tetrafluoroethylene (Nafion®), lignin, succinic acid, chitosan and/or inorganic coatings comprising oxides and metals. Metal-air flow battery according to one of the preceding claims, characterized in that the particle-laden flow is further implemented with the addition of high active area carbon particles of the order of 20-1000 m2 g_1 providing a percolated slurry with high electronic conductivity of 10-100 mS cm-1, and the concentration of carbon particles is comprised between 0.1 wt.% and 10 wt.%. Metal-airflow battery according to claim 4, characterized in that the high active area carbon particles are carbon black, graphene, expanded graphite, reduced graphene 15 oxide, active carbon, acetylene black, carbon nanotubes and a combination of two or more thereof. Metal-air flow battery according to one of the preceding claims, characterized in that different additives are introduced in the solution as Fh suppressing agents and leveling agents, comprising silicates, Pb, Bi, Sn, In, oxides and boric acid and dextrins and thickeners, comprising sodium alginate, xanthan gum and polyacrylic acid (PAA). Metal-air flow battery according to one of the preceding claims, in which the alkaline gel polymer electrolyte (GPE) is based on polyvinyl alcohol (PVA), polyacrylic acid (PAA) or polyacrylamide (PAM) or a combination of them, swelled in or containing an alkaline solution based on hydroxide salts. Metal-air flow battery according to one of the preceding claims, in which the alkaline composite polymer electrolyte (CPE) is based on polyvinyl (PVA), polyacrylic acid (PAA) or polyacrylamide (PAM) or combination of them, swelled in or containing an alkaline solution based on hydroxide salts and organic/inorganic reinforcing particles with different aspect ratio (e.g. rod, wire, fiber, dot) comprising fibers, oxides, fluorine-based polymeric particles, MOFs, carbides. Process for obtaining an air cathode for a Metal-Air flow battery according to one of the preceding claims, characterized that sequential step are being taken, namely: a) an electrochemical etching treatment is previously done on the nickel net, used as current collector, b) the catalytic materials are electrodeposited onto the nickel net at 10-50 mA cnr 2 for 10-30 minutes in two steps: a first manganese oxide (MnOx) layer in the alpha phase, as the Oxygen Reduction Reaction (ORR) catalyst and a second layer of transition metal oxides, hydroxides and oxyhydroxides comprising Ni, Fe, Co and a combination of those on top as the Oxygen Evolution Reaction (OER) catalyst, c) a final heat treatment at temperature comprised between 300 °C and 500 °C, in controlled atmosphere or in air, for a duration between 1-4 h. 16 Use of a metal-air battery according to one of claims 1 to 9 for the propulsion of vehicles on land, on water, in the air. Use of a metal-air battery according to one of claims 1 to 9 for the powering of consumer electronics, power tools, measuring instruments vehicles, the propulsion of partly or fully electrically powered bicycles, motorcycles, cars, trucks, baggers, cranes on land, partly or fully electrically powered boats, ships, submarines on or in water, partly or fully electrically powered aircraft such as helicopters, ultralight planes, microlight planes, ecolight planes, single and multiengine planes, fighters, transportation planes, airliners, hot air and gas balloons and airships in the air, space application, as permanent rechargeable power sources for houses and industrial sites, military applications, power systems of all sorts.
PCT/EP2021/062855 2020-05-14 2021-05-14 Metal-air rechargeable flow battery with zn-based nanoelectrofuel and process for obtaining an air cathode for such metal-air flow battery WO2022237990A1 (en)

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US18/560,785 US20240222744A1 (en) 2021-05-14 2022-05-16 Metal-Air Rechargeable Flow Battery
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