All carbon based high energy lithium-ion capacitors from biomass: The role of crystallinity

We report all carbon-based high energy Li-ion capacitor from environmentally threatening bio-source, prosopis juliflora. The pyrolyzed carbon exhibits a few layers of graphene-like structure and tubular morphology with multiple inherent heteroatoms like N, S, and Ca. Presence of such heteroatoms are certainly beneficial to the betterment of electrical conductivity, and pore generation which eventually results in an enhancement in capacity/capacitance of carbonaceous materials. The electrochemical pre-lithiation strategy is used to mitigate the irreversibility observed, and eventually employed as a negative electrode in a hybrid configuration. This LIC delivered a high energy density of ∼216 and 185 Wh kg⁻¹ at ambient (25 °C) and elevated temperature (55 °C) conditions, respectively. Further, ∼94% initial capacity is retained after 5000 cycles with minimum fading of 0.0013% per cycle at ambient temperature. This results clearly demonstrate that the surface functionality and heteroatom doping with tubular structure synergistically facilitates the Li⁺ and electron transport properties to realize higher energy density for this fascinating all carbon-based Li-ion capacitor.