High power supercapacitors based on hierarchically porous sheet-like nanocarbons with ionic liquid electrolytes

Abstract

Supercapacitors with ionic liquid (IL) electrolytes can reach high work voltage and accompanied high energy density, which are the critical parameters for supercapacitors’ rapid development. However, supercapacitors with IL electrolytes usually suffer from low power density due to low conductivity, large ionic size and high viscosity of the electrolytes. Herein we reported hierarchically porous sheet-like nanocarbons (HPSNCs) prepared by direct activation of graphene oxide and polytetrafluoroethylene (PTFE) polymer are promising electrode materials for high power supercapacitors with also high energy density. During the activation process, the PTFE particles as a spacer that can effectively hinder the restack of graphene oxide and simultaneously transformed into sheet-like nanocarbons at high temperatures. As a result, the as-prepared samples exhibit highest surface area of∼2000m2g−1 and largest pore volume of 1.90cm3g−1. Benefit from hierarchically porous structure from micro-to-macro-pores, which largely shorten the diffusion distance of electrolyte ions, the HPSNC electrodes show a high energy density of 51.7Whkg−1 at a power density of 35kWkg−1 in symmetric supercapacitors with IL electrolyte. In addition, the HPSNC-based supercapacitors also possess an excellent cycling stability with 88% capacitance retention after 5000 cycles. Unambiguously, this work demonstrated the potential of HPSNCs for high power supercapacitors with high energy density and application in integrated energy management electronics.