Electrolyte for supercapacitor and high-power battery use

An electrochemical cell comprising:

• a nitrile-based solvent based electrolyte, wherein
• the electrochemical cell includes an electrolyte salt that comprises NaClO4, the electrolyte salt concentration in a discharge state is greater than 1.5,
• the electrolyte salt has a maximum electrolyte conductivity at a discharge state Molar concentration greater than 1;
• wherein
• i) the electrolyte salt further comprises a sodium containing co-salt having a co-salt ratio between 0.5:1 and 32:1;
• and/or
• ii) the electrolyte salt concentration in the discharge state is less than 3.5.