Environmentally friendly zinc/aqueous polysulfide rechargeable flow battery with high energy efficiency

A zinc-polysulfide rechargeable flow battery comprising:

• a first half-cell comprising a first electrolyte containing a source of Zn2+ ions and a static or flowable electrode disposed within the first half-cell, said first half-cell being connected in a closed-loop configuration through a first pump to a first external tank containing the first electrolyte;
• a second half-cell comprising a second electrolyte in which polysulfides are dissolved and a static or flowable electrode, disposed within the second half-cell, said second half-cell being connected in a closed-loop configuration through a second pump to a second external tank containing the second electrolyte;
• in the second half-cell, a catalyst on the surface of the static electrode or dispersed in the second electrolyte in the form of particles and
• a separator between the two half-cells,
• wherein said first electrolyte further comprises one or more of:
• a salt, oxide or hydroxide of one or more metals capable of shifting the zinc electrochemical potential and to increase the overvoltage of hydrogen evolution, selected among Pb, Mn, Sn, Fe, Ni, Cu, Mg, Ti, Co, Al, Li, Zr, in a concentration ranging from 0.001 M to 1 M;
• a hydrogen evolution suppressor selected among silicates, boric acid, the metals Pb, Bi, Mn, W, Cd, As, Sb, Sn or In, the oxides of said metals, or a combination thereof, in an overall concentration in the range between 0.001 M to 5 M;
• Rochelle salts in a concentration between 0.001 M and 10 M;
• a leveling agent selected among polyethylene glycol, polyethyleneimine, thiourea, quaternary ammonium salts, dextrins, cyclodextrins, sucrose,
• polytetrafluoroethylene, sodium dodecyl sulfate, polyacrylic acid, glucose, cellulose and combinations thereof, with a concentration between 0.0001 ppm to 10000 ppm;
• a plasticizer additive selected among polyols, ethylene glycol, diethylene glycol, tetraethylene glycol, propylene glycol, glycerol, mannitol, sorbitol, xylitol, monosaccharides, fatty acids, urea, ethanolamine, triethanolamine, vegetable oils, lecithin, waxes, amino acids, surfactants or oleic acid, in a range between 0.1% by weight and 5% by weight of the first electrolyte;
• a thickener additive in a range between 0.0001% to 10% by weight of the first electrolyte;
• or
• an organic additive selected among xanthan gum, gum arabic, carboxymethyl cellulose, chitosan, agar-agar, sodium alginate or polyethylene oxide in an amount between 0.0001% to 10% by weight of the first electrolyte.

A zinc-polysulfide rechargeable flow battery comprising:

• a first half-cell comprising a first electrolyte containing a source of Zn2+ ions and a static or flowable electrode disposed within the first half-cell, said first half-cell being connected in a closed-loop configuration through a first pump to a first external tank containing the first electrolyte;
• a second half-cell comprising a second electrolyte in which polysulfides are dissolved and a static or flowable electrode, disposed within the second half-cell, said second half-cell being connected in a closed-loop configuration through a second pump to a second external tank containing the second electrolyte;
• in the second half-cell, a catalyst on the surface of the static electrode or dispersed in the second electrolyte in the form of particles and
• a separator between the two half-cells,
• wherein said second electrolyte is selected from the group consisting of:
• A) a second electrolyte further comprising:
• a solvent selected between water and a water-based mixtures containing at least 40% by volume of water with one or more compounds selected among C1-C4 alcohols, ethylene glycol, acetic acid, glycerol, or a combination of two or more thereof,
• one or more compounds selected among sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide or bismuth hydroxide, in an overall concentration between 0.01 M and 20 M;
• and
• organic and/or inorganic sulfide-based electroactive particles containing sulfide ions and decorated by catalyst particles, in an amount in the range from 0.01% by weight to 50% by weight;
• B) a second electrolyte further comprising:
• a solvent selected between water and a water-based mixtures containing at least 40% by volume of water with one or more compounds selected among C1-C4 alcohols, ethylene glycol, acetic acid, glycerol, or a combination of two or more thereof;
• one or more compounds selected among sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide or bismuth hydroxide, in an overall concentration between 0.01 M and 20 M;
• and
• organic and/or inorganic sulfide-based electroactive particles containing sulfide ions acting as source of polysulfide ions, in an amount in the range from 0.01% by weight to 50% by weight;
• and further comprises at least one of:
• catalytic particles in an amount from 0.001% by weight to 10% by weight of the second electrolyte;
• conductive particles selected from graphene, expanded graphite, reduced graphene oxide, active carbon, carbon blacks, acetylene black, carbon nanotubes or a combination of two or more thereof in an overall concentration from 0.01% by weight to 20% by weight of the second electrolyte;
• or
• conductive particles decorated by catalyst particles, wherein the conductive particles are selected among graphene, expanded graphite, reduced graphene oxide, active carbon, carbon blacks, acetylene black, carbon nanotubes or a combination of two or more thereof, and wherein said conductive particles decorated by catalyst particles are present in a concentration from 0.01% by weight to 20% by weight of the second electrolyte;
• C) a second electrolyte further comprising one or more of:
• a plasticizer additive selected among polyols, ethylene glycol, diethylene glycol, tetraethylene glycol, propylene glycol, glycerol, mannitol, sorbitol, xylitol, monosaccharides, fatty acids, urea, ethanolamine, triethanolamine, vegetable oils, lecithin, waxes, amino acids, surfactants or oleic acid, in a range between 0.1% by weight and 5% by weight of the second electrolyte;
• a thickener additive in a range between 0.0001% to 10% by weight of the first electrolyte;
• or
• an organic additive selected among xanthan gum, gum arabic, carboxymethyl cellulose, chitosan, agar-agar, sodium alginate or polyethylene oxide in an amount between 0.0001% to 10% by weight of the first electrolyte.