AQUEOUS REDOX-ENHANCED ELECTROCHEMICAL CAPACITORS: DESIGN PRINCIPLES FOR HIGH SPECIFIC ENERGIES AND SLOW SELF-DISCHARGE

摘要

Electrochemical double-layer capacitors (EDLCs) store energy at the double layer solid-electrolyte interface, typically using high-surface-area activated carbon electrodes and a non-aqueous liquid electrolyte. EDLCs are now used commercially in applications that require high power density and long-term cycle stability, for example, in load-leveling and for "stop-start" in electric vehicles. The high power and long-term cycle stability are enabled by the charging mechanism which relies on physical ion adsorption/desorption in the Helmholtz layer of the liquid electrolyte. It does not require driving slower solid-state ion insertion/de-insertion reactions as in, e.g. Li-ion batteries, which also lead to electrode volume change and thus capacity fade with cycling. Commercialized EDLC technology uses organic electrolytes, which allows for operation near 3 V in the charged state.