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

Abstract

A zinc-ion hybrid supercapacitor (ZHSC) has been 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, current ZHSC devices are hindered by several obstacles that must be overcome, such as inadequate energy density and poor cycling performance. Being a renewable carbon source, olive leaves present the advantages of abundant resources, low cost, and stable composition. The derived carbon material possesses a 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 mA h 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.