Abstract: Disclosed herein are novel, high salt concentration, sulfolane based electrolytes with a sulfone cosolvent(s), which are at their eutectic concentrations to lower the melting points of the electrolytes. The lower melting point electrolytes improve the low temperature performance of high voltage rechargeable batteries. The high salt concentration electrolytes improve the cycle performance of rechargeable lithium metal anode based batteries. The same electrolytes can operate above 4.3 V and up to 5.0 V vs. Li/Li+. Various cells containing said electrolytes are also disclosed herein.