High-yield 2D Porous Carbon Framework for High-Performance Supercapacitors with High Withstanding Voltage

Low energy density is the fatal shortcoming of supercapacitors. It is a great challenge to construct ultra-stable porous carbon which can withstand ultrahigh voltage larger than 2.7 V in organic electrolyte. Herein, 2D porous carbon framework (PCF) with high carbon yield of 22.2% is synthesized from sulfonated pitch by simple interfacial self-assembly and activation annealing strategy. It is bestowed with ultrathin thickness of 5 nm, high packing density of 0.541 g cm(-3), high specific surface area of 2511 m(2) g(-1) and high sp(2) carbon content of 89%. More importantly, it has low surface oxygen atom content of 9.74 at.% and the surface oxygen-containing functional groups mainly exist in the form of stable ether, quinone and carbonyl groups. Consequently, this PCF can successfully operate at ultrahigh voltage of 3.2 V and 3.5 V in TEABF(4)/PC and EMIMBF4 electrolytes, respectively. In TEABF(4)/PC electrolyte, it can obtain high C-g of 125 F g(-1) at 50 mA g(-1) with rate capacity C-10/0.05 as high as 76%. Satisfactorily, it can maintain high performance throughout the cycle life with 94.3% capacitance retention at 2.5 A g(-1) after 20,000 cycles. Additionally, the energy density up to 60.9 Wh kg(-1) (32.9 Wh L-1) can be achieved in EMIMBF4 electrolyte.