| Topics dealing with the advancement of the aqueous-lithium battery technology are discussed. First, results are presented from the characterization of various cathode candidates for the aqueous-lithium systems: both water and oxygen reducing. Among the water reducing cathodes, nickel and ruthenium cathodes have proven to be the best candidates. Planar nickel and ruthenium electrodes have been studied in 8M KOH using electrochemical impedance spectroscopy (EIS) and equivalent circuits at -1.2, -1.25, -1.35, -1.45, and -1.7 VSCE. Aging characteristics based on EIS are presented for the nickel and ruthenium electrodes at -1.25 and -1.45 V SCE. Electrochemical rate constants are also reported from the EIS data, which are based on the Volmer-Heyrovsky mechanism of the hydrogen evolution reaction (HER). The kinetic parameters obtained from the mechanistic model agree with both the AC results obtained at all five cathodic overpotentials tested and the DC experimental results form nickel in 8M KOH. Among the oxygen reducing cathodes, four commercially available air cathodes form E-TEK, ERC, and Alupower were used to characterize the lithium-air system for a wide range of discharge rates. Secondly, a commercially available cation exchange membrane, NafionRTM 90209, has proven to be an effective means of controlling the electrolyte concentration of the battery if operating in an ocean environment. Finally, the characterization of aqueous-lithium single-celled batteries is presented for both lithium-air and lithium-water batteries. A novel idea for a lithium-water battery is also described, and results are presented for 8 days of continuous prototype operation. The specific energy density of the prototype, 4 kW-hr/kg, has almost doubled that of previous designed lithium-water systems, and the faradaic efficiency of the prototype exceeds 90%. The lithium-water prototype demonstrated that the system is promising, and efforts should continue for its development. |
