A highly-concentrated electrolyte system for an electrochemical cell is provided, along with methods of making the electrolyte system. The electrolyte system includes a bound moiety having an ionization potential greater than an electron affinity and comprising one or more salts selected from the group consisting of: lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, potassium bis(fluorosulfonyl)imide, and combinations thereof bound to a solvent comprising one or more solvents selected from the group consisting of: dimethyl carbonate, dimethyl dicarbonate, and combinations thereof. The salts have a concentration in the electrolyte system of greater than or equal to about 4 M. A molar ratio of the salts to the dimethyl carbonate is about 0.5. A molar ratio of the salts to the dimethyl dicarbonate is about 1. The salts binds to the dimethyl carbonate and/or dimethyl dicarbonate causing the electrolyte system to be substantially free of unbound dimethyl carbonate, unbound dimethyl dicarbonate, and unbound bis(fluorosulfonyl)imide.