N, O-codoped hierarchical porous carbons derived from algae for high-capacity supercapacitors and battery anodes

Abstract

Nitrogen and oxygen codoped hierarchical porous carbons have been synthesized by using a direct carbonization/activation procedure of biomass algae – Enteromorpha. The proposed procedure allowed us to produce carbons with high surface area (up to 2073 m² g⁻¹), sponge-like 3D interconnected structure, combined macro/meso/micropores, and rich N (0.64–0.85 at%) and O (11.36–12.24 at%) doping. The application of the produced carbons in supercapacitors based on an ionic liquid electrolyte showed a high specific capacitance of 201 F g⁻¹ (10.7 μF cm⁻²) at 1 A g⁻¹ and 20 °C, a capacitance retention ratio of 61% at 100 A g⁻¹ and a capacitance loss of 9% after 10 000 cycles. The devices were able to deliver an energy density of 24 or 35 W h kg⁻¹ (on an active mass normalized basis) at an extremely high power density of 60 kW kg⁻¹ at 20 or 60 °C. The application of the produced carbons in a lithium-ion battery anode based on the LiPF₆ electrolyte exhibited a high specific capacity of 1347–1709 mA h g⁻¹, a good initial coulombic efficiency of 61–64%, and a good cyclability up to 500 cycles. We believe that this simple precursor-synthesis route offers excellent potential for facile large-scale material production for supercapacitors and lithium ion batteries.