Hierarchically Porous Carbon as a High‐Rate and Long‐Life Electrode Material for High‐Performance Supercapacitors

Abstract

In this study, cost‐effective hierarchically porous carbon (HPC) derived from starch was successfully prepared through a simple mixing and subsequent one‐step carbonization method. Based on the three‐dimensional interconnected hierarchically porous structure, HPC exhibits a high specific surface area of 2259.54 m2 g−1 and a specific capacitance of 385.7 F g−1 at 1 A g−1 in a three‐electrode system. When the as‐prepared carbon was employed to fabricate an aqueous symmetrical supercapacitor, the device displayed a high specific capacitance of 81.3 F g−1 at 1 A g−1, and even at 20 A g−1 the specific capacitance remained 64 F g−1 (capacity retention rate of 78.72 % compares with that at 1 A g−1), demonstrating an outstanding rate performance. This supercapacitor maintained a capacity retention of 100 % after 60 000 cycles at a current density of 5 A g−1, indicating superior long‐term cycling stability. Furthermore, when the as‐prepared carbon was employed to fabricate a symmetrical supercapacitor in ionic liquid (1‐ethyl‐3‐methylimidazolium tetrafluoroborate, EMIMBF4) electrolyte, it ultimately achieved an ultrahigh energy density of 133.94 Wh kg−1 (power density of 1997.51 W kg−1) and a capacity retention rate of 83.3 % was maintained after 5000 cycles throughout a wide operating potential window of 0–4 V at 10 A g−1.

Biomass-Derived Porous Carbon Materials for Supercapacitor

“…Direct carbonization of starch with the aid of activated agents is easy and commonly used by researchers for preparing PC. Guo (Guo et al, 2018) synthesized starch-derived PC through one-pot carbonization, the as-prepared PC achieved a C s of 385 F/g at 1 A/g. Zhang (Zhang et al, 2015b) proposed a simple strategy to fabricate hierarchical hollow porous spherical carbon using starch as raw materials and KHCO 3 as the activation agent.…”

Biomass-derived porous carbon materials: synthesis, designing, and applications for supercapacitors

“…51 So far, a considerable number of materials, including various carbon materials, carbon materials/conductive polymers, carbon materials/metal oxides, etc., have been used as electrode materials for manufacturing supercapacitors. [53][54][55][56][57][58][59][60][61][62][63][64] The voltage window of symmetric supercapacitors is limited by the voltage window of the electrode material, which limits the power density and energy density. 51 In contrast, the voltage window of asymmetric supercapacitors is the sum of the voltage windows of the positive and negative electrodes.…”

Three-Dimensional Interconnected Reticular Porous Carbon From Corn Starch By a Sample Sol–Gel Method Toward High-Performance Supercapacitors With Aqueous and Ionic Liquid Electrolytes

“…Except for the specific capacitance, the energy density of supercapacitors is also closely related to the potential operating window of the electrolyte. Although aqueous electrolytes are cheap and highly conductive, which can achieve the high specific capacitance, the low decomposition potential of water limits its working voltage. , Fortunately, nonaqueous electrolytes including the organic electrolyte and ionic liquid can provide a wide potential window. The organic electrolyte is too expensive and strongly toxic, while ionic liquids exhibit not only wide decomposition voltages but also provide excellent conductivity and thermal stability.…”

“…Although aqueous electrolytes are cheap and highly conductive, which can achieve the high specific capacitance, the low decomposition potential of water limits its working voltage. , Fortunately, nonaqueous electrolytes including the organic electrolyte and ionic liquid can provide a wide potential window. The organic electrolyte is too expensive and strongly toxic, while ionic liquids exhibit not only wide decomposition voltages but also provide excellent conductivity and thermal stability. Thus, using the ionic liquid as an electrolyte is of great significance for the improvement of the energy density of supercapacitors from their practical application view.…”