COSOLVENT ELECTROLYTES FOR ELECTROCHEMICAL DEVICES
A system and method for stabilizing electrodes against dissolution and/or hydrolysis including use of cosolvents in liquid electrolyte batteries for three purposes: the extension of the calendar and cycle life time of electrodes that are partially soluble in liquid electrolytes, the purpose of limiting the rate of electrolysis of water into hydrogen and oxygen as a side reaction during battery operation, and for the purpose of cost reduction.
1 . A rechargeable electrochemical system having a pair of electrodes disposed within a liquid electrolyte of a total volume V having a first volume fraction V 1 consisting essentially of H 2 O wherein at least one of the electrodes includes a transition metal cyanide coordination compound (TMCCC) material having a first dissolution rate R 1 in the liquid electrolyte when the first volume fraction V 1 divided by the total volume V is greater than 0.50, the improvement comprising:
a second volume fraction V 2 of the total volume V including one or more organic cosolvents;
wherein V=V 1 +V 2 ;
wherein V 2 >V 1 ;
wherein V 1 /V>0.02
wherein V 1 /V<0.50;
wherein the liquid electrolyte consists essentially of a single phase; and
wherein the at least one electrode includes a second dissolution rate R 2 <R 1 when V=V 1 +V 2 and V 2 >V 1 and V 1 /V>0.02 and the liquid electrolyte consists essentially of a single phase.
2 . The rechargeable electrochemical system of claim 1 wherein the TMCCC material includes a composition having the general chemical formula A x P y [R(CN) 6-j L j ].nH 2 O, wherein:
A includes one or more cations;
P includes one or more metal cations;
R includes one or more transition metal cations; and
L is a ligand substituted in the place of a CN ligand; where
0≦x≦2;
0<y≦4;
0<z≦1;
0≦j≦6; and
0≦n≦5.
3 . The rechargeable electrochemical system of claim 2 wherein:
said A cations include one or more cations selected from the group consisting of Na + , K + , Li + , NH 4+ , Me 2+ Ca 2+ and combinations thereof;
said P metal cations include one or more metal cations selected from the group consisting of Ti 3+ , Ti 4+ , V 2+ , V 3+ , Cr 2+ , Cr 3+ , Mn 2+ , Mn 3+ , Fe 2+ , Fe 3+ , Co 2+ , Co 3+ , Ni 2+ , Cu + , Cu 2+ , Zn 2+ , Al 3+ , Sn 2+ , In 3+ , or Pb 2+ and combinations thereof;
said R transition metal cations include one or more transition metal cations selected from the group consisting of V 2+ , V 3+ , Cr 2+ , Cr 3+ , Mn + , Mn 2+ , Mn 3+ , Fe 2+ , Fe 3+ , Co 2+ , CO 3+ , Ru 2+ , Ru 3+ , Os 2+ , Os 3+ , Ir 2+ , Ir 3+ , Pt 2+ , Pt 3+ , and combinations thereof; and
said L ligands include one or more ligands selected from the group consisting of CO (carbonyl), NO (nitrosyl), Cl − , and combinations thereof.
4 . The rechargeable electrochemical system of claim 1 wherein the total liquid volume V includes one or more cations selected from the group consisting of an alkali cation, an alkali earth cation, an ammonium cation, and combinations thereof.
5 . The rechargeable electrochemical system of claim 4 wherein the liquid electrolyte produces a total concentration of said plurality of cations in the total liquid volume V greater than 0.1 M.
6 . The rechargeable electrochemical system of claim 5 wherein said total concentration is greater than 1.4 M.
7 . The rechargeable electrochemical system of claim 1 wherein the total liquid volume V includes an electrode lifetime extending additive; wherein an electrode disposed within the total liquid volume V includes a first lifetime when disposed in the total liquid volume V, wherein said electrode includes a second lifetime when disposed in the total liquid volume without said additive, and wherein said lifetime is greater than said second lifetime.
8 . The rechargeable electrochemical system of claim 1 wherein the total liquid volume V includes one or more organic polar aprotic solvents.
9 . The rechargeable electrochemical system of claim 8 wherein said one or more organic polar aprotic cosolvents include a particular cosolvent having one or more cyanide groups.
10 . The rechargeable electrochemical system of claim 9 wherein said particular cosolvent includes acetonitrile.
11 . The rechargeable electrochemical system of claim 8 wherein said one or more organic polar aprotic cosolvents include a particular cosolvent having one or more carbonate groups.
12 . The rechargeable electrochemical system of claim 11 wherein said particular cosolvent is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, and combinations thereof.
13 . The rechargeable electrochemical system of claim 1 wherein the total liquid volume V includes one or more organic polar protic solvents.
14 . The rechargeable electrochemical system of claim 13 wherein said one or more organic polar protic solvents include a particular solvent having one or more alcohol groups.
15 . The rechargeable electrochemical system of claim 14 wherein said particular solvent is selected from the group consisting of methanol, ethylene glycol, glycerol, hydroxypropionitrile, and combinations thereof.
16 . The rechargeable electrochemical system of claim 1 wherein V 1 /V≦30% and V 2 /V≧≧70%.
17 . The rechargeable electrochemical system of claim 16 wherein V 1 /V≦10% and V 2 /V≧90%.
18 . The rechargeable electrochemical system of claim 8 wherein the total liquid volume V includes both a cyanide-containing cosolvent and a carbonate-containing cosolvent.
19 . The rechargeable electrochemical system of claim 8 wherein said one of more organic polar aprotic cosolvents include a particular cosolvent having one or more sulfone groups.
20 . The rechargeable electrochemical cell of claim 19 wherein said particular cosolvent includes sulfolane.
21 . The rechargeable electrochemical system of claim 8 wherein the total liquid volume V includes both a cyanide-containing cosolvent and a sulfone-containing cosolvent.
22 . The rechargeable electrochemical system of claim 1 wherein said second volume fraction V 2 includes a first volume subfraction V 3 and a second volume subfraction volume V 4 wherein V 3 +V 4 =V 2 , wherein said first volume subfraction V 3 includes a first organic cosolvent, and wherein said second volume subfraction V 4 includes a second organic cosolvent different from said first organic cosolvent.
23 . The rechargeable electrochemical system of claim 22 wherein said first organic cosolvent includes MeCN, and wherein said second organic cosolvent includes a solvent selected from the group consisting essentially of sulfolane, propylene glycol monoethyl ether, hydroxypropionitrile, gamma-valerolactone, ethylene carbonate, dimethyl carbonate, propylene carbonate, and 1,3-dioxolan.
24 . The rechargeable electrochemical system of claim 23 wherein V 1 /V=0.05, wherein V 3 /V≧0.10, and wherein V 4 /V≦0.85.