Electrochemical energy storage systems and methods featuring optimal membrane systems

A flow battery, comprising:

• a first electrolyte comprising an aqueous solution comprising a first active material and at least one mobile ion;
• a second electrolyte comprising an aqueous solution comprising a second active material and at least one mobile ion;
• wherein at least one of the first active material and the second active material comprises a metal ligand coordination compound comprising a chelating organic ligand and the metal ligand coordination compound bears a negative ionic charge;
• the first electrolyte is substantially free of the second active material and the second electrolyte is substantially free of the first active material;
• a first electrode in contact with said first electrolyte;
• a second electrode in contact with said second electrolyte;
• and
• a separator having a thickness of about 100 microns or less;
• wherein the flow battery is capable of operating with a round trip voltage efficiency of at least 60% with a current density of at least about 100 mA/cm2,
• wherein the separator comprises a porous membrane having pores with an average size distribution of between about 0.001 nm and 100 nm, and
• wherein the at least one of the first active material and the second active material have an average diameter that is about 50% greater than an average pore size of the porous membrane.

A flow battery, comprising:

• a first electrolyte comprising an aqueous solution comprising a first active material and at least one mobile ion;
• a second electrolyte comprising an aqueous solution comprising a second active material and at least one mobile ion;
• wherein at least one of the first active material and the second active material comprises a metal ligand coordination compound comprising a chelating organic ligand and the metal ligand coordination compound bears a negative ionic charge;
• the first electrolyte is substantially free of the second active material and the second electrolyte is substantially free of the first active material;
• a first electrode in contact with said first electrolyte;
• a second electrode in contact with said second electrolyte;
• and
• a separator of thickness of about 100 microns or less having a selectivity in a range of about 50 to about 1,000,000 for one mobile ion over the first and second active materials;
• wherein the flow battery is capable of operating with a current efficiency of at least 85% with a current density of at least about 100 mA/cm2,
• wherein the separator comprises a porous membrane having pores with an average size distribution of between about 0.001 nm and 100 nm, and
• wherein the at least one of the first active material and the second active material have an average diameter that is about 50% greater than an average pore size of the porous membrane.

A flow battery, comprising:

• a first electrolyte comprising an aqueous solution comprising a first active material and at least one mobile ion;
• a second electrolyte comprising an aqueous solution comprising a second active material and at least one mobile ion;
• wherein at least one of the first active material and the second active material comprises a metal ligand coordination compound comprising a chelating organic ligand and the metal ligand coordination compound bears a negative ionic charge;
• the first electrolyte is substantially free of the second active material and the second electrolyte is substantially free of the first active material;
• a first electrode in contact with said first electrolyte;
• a second electrode in contact with said second electrolyte;
• and
• a separator having a thickness of about 100 microns or less and having a diffusion rate through the separator for the first active material, the second active material, or both of 1×10−7 mol/cm2-sec or less;
• wherein the flow battery is capable of operating with a current efficiency of at least 85% with a current density of at least about 100 mA/cm2,
• wherein the separator comprises a porous membrane having pores with an average size distribution of between about 0.001 nm and 100 nm, and
• wherein the at least one of the first active material and the second active material have an average diameter that is about 50% greater than an average pore size of the porous membrane.

A flow battery, comprising:

• a first electrolyte comprising an aqueous solution comprising a first active material and at least one mobile ion;
• wherein the first active material has a net ionic charge;
• a second electrolyte comprising an aqueous solution comprising a second active material and at least one mobile ion;
• wherein the second active material has a net ionic charge, the net ionic charge of the second active material being of the same sign as the net ionic charge of the first active material;
• and
• wherein at least one of the first active material and the second active material comprises a metal ligand coordination compound comprising a chelating organic ligand and the metal ligand coordination compound bears a negative ionic charge;
• the first electrolyte is substantially free of the second active material and the second electrolyte is substantially free of the first active material;
• a first electrode in contact with said first electrolyte;
• a second electrode in contact with said second electrolyte;
• and
• a separator of thickness of about 100 microns or less, the separator comprising an ionomer membrane also having a net ionic charge;
• wherein the sign of the net ionic charges of the first and second active materials matches that of the ionomer membrane;
• and wherein the flow battery is capable of operating with a current efficiency of at least 90% with a current density of at least 100 mA/cm2,
• wherein the separator comprises a porous membrane having pores with an average size distribution of between about 0.001 nm and 100 nm, and
• wherein the at least one of the first active material and the second active material have an average diameter that is about 50% greater than an average pore size of the porous membrane.

A flow battery, comprising:

• a first electrolyte comprising an aqueous solution comprising a first active material and at least one mobile ion;
• a second electrolyte comprising an aqueous solution comprising a second active material and at least one mobile ion;
• wherein at least one of the first active material and the second active material comprises a metal ligand coordination compound comprising a chelating organic ligand and the metal ligand coordination compound bears a negative ionic charge;
• the first electrolyte is substantially free of the second active material and the second electrolyte is substantially free of the first active material;
• a first electrode in contact with said first electrolyte;
• a second electrode in contact with said second electrolyte;
• and
• a separator of thickness of about 100 microns or less, wherein the separator has a plurality of layers wherein at least one layer is capable of ionic conduction and at least one other layer is capable of selective ion transport;
• and wherein the flow battery is capable of operating with a current efficiency of at least 90% with a current density of at least about 100 mA/cm2,
• wherein the separator comprises a porous membrane having pores with an average size distribution of between about 0.001 nm and 100 nm, and
• wherein the at least one of the first active material and the second active material have an average diameter that is about 50% greater than an average pore size of the porous membrane.