In some designs, it may be advantageous to have a total salt concentration in the electrolyte in the range from around 0.8M to around 2.0M (preferably, in the range from around 1.0M to around 1.8M), while utilizing a small fraction of at least one at least partially fluorinated solvent (for example, as a component of the RMP solvents) in the electrolyte mixture in the range from around 1 to around 30 vol. %, as a fraction of all the solvents in the electrolyte (in some designs, from around 3 vol. % to around 20 vol. %). It may be further advantageous for the electrolyte solvent mixture to comprise both linear and cyclic molecules. In an example, it may be advantageous for at least one of the cyclic molecules to comprise fluorine atoms. In some designs, it may be preferred for the electrolyte to comprise a fluoroethylene carbonate (FEC) co-solvent in electrolyte (e.g., in the range from around 1 to around 30 vol. %, as a fraction of all the solvents in the electrolyte). It may further be advantageous for the electrolyte solvent to comprise a mixture of LMP and RMP solvents and (optionally) ADD solvents. In some designs, it may also be advantageous for the LMP solvent or solvent mix to comprise ester(s). In some designs, it may also be advantageous for at least one of the solvents in the LMP solvent or solvent mix to be at least partially fluorinated. In some designs, it may also be advantageous for the electrolyte to comprise other cyclic carbonates in addition to FEC (e.g., as other components of the RMP solvents). In some designs, it may be advantageous for the other cyclic carbonates to comprise ethylene carbonate (EC) with the melting point of about +34-37° C. or another cyclic carbonate with a high melting point (e.g., above +25° C.). Furthermore, in an example, the vol. ratio of FEC to other cyclic carbonates may preferably be in the range from about 4:1 to about 1:40. In an example, the exact optimal ratio may depend on the electrode characteristics (e.g., thickness, amount of binder, density, anode and cathode composition and capacity, etc.), electrolyte solvent mix utilized and/or cell cycling regime (temperature, voltage range, etc.).