Carbonate-based electrolyte system improving or supporting efficiency of electrochemical cells having lithium-containing anodes

A method of improving or optimizing anodic stability of an electrochemical cell that cycles lithium-ions and comprises a positive electrode comprising a positive lithium-based electroactive material having a maximum potential greater than or equal to about 5V and a negative electrode having a negative electroactive material comprising lithium, the method comprising:

• introducing an electrolyte system into the electrochemical cell, the electrolyte system comprising a bound moiety having an ionization potential greater than an electron affinity and comprising one or more salts bound to a solvent, wherein the one or more salts has a concentration in the electrolyte system of greater than or equal to about 4M and is selected from the group consisting of:
• lithium bis(fluorosulfonyl)imide (LiFSI), sodium bis(fluorosulfonyl)imide (NaFSI), potassium bis(fluorosulfonyl)imide (KFSI), and combinations thereof and the solvent comprises one or more solvents selected from the group consisting of:
• dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), and combinations thereof, wherein when dimethyl carbonate (DMC) is present in the electrolyte system, a molar ratio of the one or more salts to the dimethyl carbonate (DMC) is about 0.5 and when dimethyl dicarbonate (DMDC) is present in the electrolyte system, a molar ratio of the one or more salts to the dimethyl dicarbonate (DMDC) is about 1, and the electrolyte system is substantially free of unbound dimethyl carbonate (DMC), unbound dimethyl dicarbonate (DMDC), and unbound bis(fluorosulfonyl)imide (FSI−).

An electrochemical cell that cycles lithium-ions having improved or optimized efficiency comprising:

• a positive electrode comprising a positive lithium-based electroactive material and having a maximum potential greater than or equal to about 5V;
• a separator;
• a negative electrode comprising a negative electroactive material comprising lithium;
• and
• an electrolyte system comprising a bound moiety having an ionization potential greater than an electron affinity and comprising one or more salts bound to a solvent, wherein the one or more salts is selected from the group consisting of:
• lithium bis(fluorosulfonyl)imide (LiFSI), sodium bis(fluorosulfonyl)imide (NaFSI), potassium bis(fluorosulfonyl)imide (KFSI), and combinations thereof and the solvent comprises one or more solvents selected from the group consisting of:
• dimethyl carbonate (DMC), dimethyl dicarbonate (DMDC), and combinations thereof, wherein the one or more salts have a concentration in the electrolyte system of greater than or equal to about 4M, and wherein the electrolyte system is substantially free of unbound dimethyl carbonate (DMC), unbound dimethyl dicarbonate (DMDC), and unbound bis(fluorosulfonyl)imide (FSI−).