The application of supercapacitors for objectives such as automobiles requires high voltage and high temperature operation, therefore development of new electrode materials that have sufficient stability under such harsh conditions is crucial. In this work, we report the development of seamless mesoporous carbon sheet consisting of continuous graphene walls, which exhibits extraordinarily high stability under high voltage and high temperature conditions. The sheet contains very few carbon edge sites (only 4% of the number present in conventional activated carbons) despite its high specific surface area (1500 m2 g−1), and it is possible to use it to assemble symmetric supercapacitors with excellent stability under 3.5 V@60 °C and 4.4 V@25 °C conditions, even using a conventional electrolyte (1 M Et3MeNBF4/propylene carbonate). Moreover, high-voltage operation at 4.4 V results in a 2.7 times higher energy density compared to that achieved using conventional activated carbons.
