Abstract: A reversible electrochemical mirror (REM) includes a first electrode and a second electrode, one of which is substantially transparent to at least a portion of the spectrum of electromagnetic radiation. An essentially nonaqueous electrolytic solution, disposed between the first and second electrodes, contains ions of an electrodepositable metal having a molar concentration of more than 0.5 M. The electrolytic solution also contains halide and/or pseudohalide anions having a total molar concentration ratio of at least 2:1 relative to the concentration of the electrodepositable metal cations. A negative electrical potential applied to the first electrode causes deposited metal to be dissolved from the second electrode into the electrolytic solution and to be electrodeposited from the solution onto the first electrode to form a mirror deposit, thereby affecting the reflectivity of the REM device for electromagnetic radiation.