Hierarchically porous activated carbons prepared via a dissipative process: a high-capacity cathode for Li-ion capacitors

Abstract

Activated carbons with high specific surface area (SSA) and well-modulated pore structure are highly desirable for achieving high-performance capacitive energy storage. Herein, hierarchically porous activated carbons (PACs) are synthesized by a tableting-activation method. The quick release of high-pressure gaseous products from the inside of the tablets can be regarded as a dissipative process, which leads to the formation of well-ordered high density meso- or macropores in the resulting material. The porous structure of the PACs has been modulated by adjusting the dissipative process parameters, such as the tableting pressure and tablet thickness. As a result, the optimal PAC (PAC-10) possesses an ultrahigh SSA (up to 3211 m² g⁻¹) and a well-developed hierarchical porous structure, which leads to an excellent capacitive energy-storage performance both in an aqueous electrolyte supercapacitor system and a Li ion capacitor (LIC) system. In particular, as a cathode for LICs, PAC-10 exhibits an extremely high specific capacity of 251 mA h g⁻¹ at 0.5 A g⁻¹ and still retains 158 mA h g⁻¹ at a high rate of 15 A g⁻¹.