Constructing graphitization graded porous carbon using olive leaves as a carbon source for high-performance zinc-ion hybrid capacitor

Abstract

Zinc-ion hybrid supercapacitor (ZHSC) is considered as an emerging sustainable electrochemical energy storage device in the past decade. It has received widespread attention due to its low price, safety and reliability. However, the obstacles that need to be overcome include the inadequate energy density and poor cycling performance for current ZHSC. It is true that olive leaves, as a renewable carbon source, present the advantages of abundant resources, low cost and stable composition. The derived carbon material possesses high surface area hierarchical graphitic structure and excellent N/O co-doping feature. The assembled Zn//OLPC-2 capacitors deliver a specific capacity of 176.2 mAh g-1 at 0.1 A g-1. They can be stably charged/discharged 15,000 times and maintain a retention rate of 96.8 % at 10 A g-1. In addition, the fabricated flexible devices also show excellent mechanical stability and durability.