Solvent-free, deep eutectic system-assisted synthesis of nanoarchitectonics of hierarchical porous carbons for high rate supercapacitors†

Abstract

Traditional battery electrode materials have insufficient high rate charging and discharging capabilities, while capacitive materials can achieve fast charging and discharging, but their energy density is low, making it difficult to meet the needs of high-performance energy storage materials and social development. Here, we propose a solvent-free assisted synthesis method of hierarchical porous carbon based on deep eutectic systems (DESs), which can ensure that DESs are immersed into the cracks/voids of polyacrylonitrile (PAN) solid particles. Rich O/N/S co-doped hierarchical porous carbon materials with an ultra-high specific surface area (3353 m² g⁻¹) and a large pore volume (1.8 cm³ g⁻¹) can be obtained by carbonizing PAN filled with low eutectic salts and forming pores with different pore sizes through the permeation and diffusion of low eutectic salts. When porous carbon was applied in supercapacitors, the final porous carbon electrode exhibits a high capacitance of 305.65 F g⁻¹ at 0.5 A g⁻¹, in a three-electrode system, with a rate performance of 154 F g⁻¹ at 200 A g⁻¹, a high energy density of 16.08 W h kg⁻¹ at a power density of 175 W kg⁻¹, and excellent cycling stability (98.02% capacity retention after 10 000 cycles at 5 A g⁻¹). The electrochemical performance of this carbon material indicates that it has the potential to become a competitive candidate electrode in high-performance supercapacitors.