Abstract: Na-rich electrolyte compositions provided herein can be used in a variety of devices, such as sodium ionic batteries, capacitors and other electrochemical devices. Na-rich electrolyte compositions provided herein can have a chemical formula of Na3OX, Na3SX, Na (3-?) M?/2OX and Na (3-?) M?/2SX wherein 0<?<0.8, wherein X is a monovalent anion selected from fluoride, chloride, bromide, iodide, H?, CN?, BF4?, BH4?, ClO4?, CH3?, NO2?, NH2? and mixtures thereof, and wherein M is a divalent metal selected from the group consisting of magnesium, calcium, barium, strontium and mixtures thereof. Na-rich electrolyte compositions provided herein can have a chemical formula of Na (3-?) M?/3OX and/or Na (3-?) M?/3SX; wherein 0<?<0.5, wherein M is a trivalent cation M3, and wherein X is selected from fluoride, chloride, bromide, iodide, H?, CN?, BF4?, BH4?, ClO4?, CH3?, NO2?, NH2? and mixtures thereof.