The effect of electrolyte additives on the rate performance of hard carbon anode at low temperature for lithium-ion capacitor

Lithium-ion capacitor (LIC), which combines the advantages of lithium-ion battery (LIB) and electrical double layer capacitor (EDLC), has a rapid development during last decade, however, the poor low temperature performance still limits its application. In this paper, three electrolyte additives including vinylene carbonate (VC), fluoroethylene carbonate (FEC) and 1,3,2-dioxathiolane 2,2-dioxide (DTD) have been utilized and their effects on the rate performance of hard carbon (HC) anode of LIC at various temperatures ranging from 25 °C to −40 °C have been well evaluated. The cell containing FEC shows the best rate performance at various temperatures and has the charge and discharge capability even at −40 °C. For HC anode, the charge transfer impedance (R_CT) increases exponentially at low temperature, while the equivalent series resistance (Rs) and the impedance of solid electrolyte interface (SEI) increase relatively few. At low temperatures, the effect of FEC may be mainly reflected in its effect on the charge transfer process.