Pitch-based 3D tremella-like porous carbon with cavitary structures: Applications in symmetric capacitors and zinc ion capacitors

The application of porous carbon in electrochemical energy storage devices (e.g., symmetrical capacitors, SCs, zinc ion capacitors, ZICs) is of great value, while pitch is one of the excellent precursors of porous carbon. Herein, the pitch-based 3D tremella-like porous carbons with heteroatoms (N and O) and cavitary structures have been synthesized via one-step oxidation activation. This strategy can introduce oxygen atoms to effectively inhibit the conjugation effect of the pitch and improve the convenience of preparation. The melting and crystallizing effect of NaCl can help the creation of cavitary structures and hierarchical pores. Gases released from the pyrolysis of pitches and decomposition of K2C2O4 contribute to the distortion of the carbon structure, resulting in the tremella-like morphology. The best sample, PC-825, has a specific capacitance of 338.5 F g−1 in a three-electrode system and an energy density of 12.2 Wh kg−1 in SCs. More importantly, PC-825 as cathodes in ZICs has a specific capacitance of up to 193.1 mAh g−1 and an energy density of up to 154.5 Wh kg−1, realizing an outstanding zinc storage capacity. This work realizes the conversion of cheap pitch to high-value-added electrochemical materials.