Synthesis and Modification of Activated Carbon Originated From Indonesian Local Orange Peel for Lithium Ion Capacitors Cathode

Abstract

Lithium ion capacitor (LIC) is a novel hybrid capacitor technology that possesses a better performance than the conventional supercapacitor, such as EDLC and lithium ion battery. However, the overall performance of LIC is limited by activated carbon’s capacity as its cathode. This work is focused on synthesize of activated carbon from Indonesian local orange peel waste for LIC cathode and its modification to perform a good electrochemical performances. Activated carbon was synthesized by ZnCl2 as impregnant with mass ratio of orange peel to ZnCl2 1:2 for 1 h at 500 °C. The obtained activated carbon possessed large surface area (1200 m2 g −1), higher than commercial activated carbon (Merck-p.a.) with surface area of 775.6 m2 g−1. Modification was done using wet oxidation method by utilizing HNO3 65 %, H2SO4 98 %, and H2O2 30 %, with ratio 1:1 (w/w). Electrochemical properties were studied by using half cell test pouch with Li metal as reference electrode and 1 M LiPF6 (EC:EMC:DMC = 1:1:1) as electrolyte. Modification had successfully increased oxygen atoms in activated carbon samples. Surface-modified cells demonstrated a higher capacitance (almost twice in the galvanostatic test) than that of the unmodifed one due to the pseudocapacitance effect of oxygen functional groups. However, its electrochemical performance was unstable. The unmodified cell showed a stable performance with 56.3 F g−1 at current density of 0.3 mA g−1 and voltage window 2.5–4 V.