Fabrication of High Energy Li–Ion Capacitors from Orange Peel Derived Porous Carbon

Activated carbon (AC) with high surface area (1,901 m² g⁻¹) is synthesized from bio-waste orange (Citrus sinensis) peel for fabrication of high specific energy lithium ion capacitors (LICs). The composition, structure and electrochemical properties of orange peel derived AC (OP-AC) are characterized by elemental analyzer, field emission-scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammogram, charge-discharge and impedance studies. Fabricated LIC using the high surface area OP-AC with pre-lithiated graphite (LiC₆) delivered specific energy of ∼106 Wh kg⁻¹. In addition, LIC configuration with Li₄Ti₅O₁₂ was also fabricated and observed to be capable of delivering the specific energy of ∼35 Wh kg⁻¹. Symmetric configuration of OP-AC with aqueous and organic solutions was also made for comparison purpose. A systematic improvement from the specific energy of ∼7 to 106 Wh kg⁻¹ is noted from aqueous to LIC assembly. The findings open up the possibility of developing high specific energy LICs from abundant, low-cost, sustainable biomass waste.