Abstract:

Lithium ion capacitors (LICs), a new type of energy storage devices, can bridge the performance gap between high-power and high-energy storage systems. In this study, pouch-type LICs were fabricated with different positive/negative (P/N) mass ratios were fabricated using activated carbon (AC) as the cathode and orthorhombic niobium pentoxide (T-Nb₂O₅) as the anode. The effect of the prelithiation ratio was investigated. Results indicate that prelithiation can effectively improve the electrochemical performance of pouch-type LICs. Regardless of the P/N mass ratio, when the prelithiation ratio was increased to 60%, the open-circuit potential increased to >1.5 V; the initial Coulombic efficiency exceeded 80%; the specific capacity of the active material improved, accompanied by reduced internal resistance; the cyclic voltammetry curves exhibited typical capacitive behavior; the voltage retention remained above 75% after 33 d of storage at room temperature; the capacity retention during C-rate testing exceeded 95% at a current of 100C; and the capacity retention during cycle life testing was >90% after 3000 cycles. A higher P/N mass ratio had a more favorable impact on LIC performance due to enhanced initial Coulombic efficiency and improved voltage retention during the self-discharge process. After 60% prelithiation, the LIC with the highest P/N mass ratio (P/N=1.1) exhibited stable energy output, achieving an energy density of 30.4 Wh/kg at a power density of 103.2 W/kg and retaining 29.4 Wh/kg at a power density of 2098.1 W/kg.

Key words: lithium ion capacitor, prelithiation, activated carbon, orthorhombic niobium pentoxide