This chapter includes elaborately selected recent literatures on electrochemical energy storing in symmetric supercapacitors (SSCs) with high operating voltages (voltage >1.6 V) and high specific energy. SSCs are a typical sort of electrochemical capacitors with larger energy density than conventional capacitors; by involving electrode materials with stable interfaces (for instance, nitrogen-doped carbon materials) and electrolytes with wide safe potential window (for instance, ionic liquids), they can supply competitive energy relative to batteries. Fundamentals of SSCs are first introduced, aiming at clarifying some critical interfacial phenomena that are critical to enhance overall capacitive performance. State-of-the-art SSCs are included as demonstrations from the aspects of both enhanced capacitances and expanded voltages. We also provide a few feasible strategies for the design high-voltage/energy SSCs such as using inactive electrode materials.
Part of the book: Supercapacitors