Tube-like carbon for Li-ion capacitors derived from the environmentally undesirable plant: Prosopis juliflora

This work describes the fabrication of high-energy Li-ion hybrid electrochemical capacitors (Li-HEC) from the environmentally threatening and invasive Prosopis juliflora. The carbon derived from this acts as the positive electrode active material in organic medium. High-surface-area carbon was obtained from P. juliflora and activated using KOH at various concentrations and temperatures. Of the tested ratios, 1:2 (carbon: KOH) treated at 900 °C (KC21-900) yielded a high specific surface area (2410 m2 g−1) and specific capacitance (∼161 F g−1). Then, a Li-HEC was fabricated with a homemade insertion-type Li4Ti5O12 negative electrode, delivering a maximum energy density of ∼80 W h kg−1. In addition, the prepared Li-HEC had excellent cycleability (10000 cycles) and good capacity retention characteristics.