Hierarchical porous activated carbon anode for dual carbon lithium-ion capacitors: Energy storage mechanisms and electrochemical performances

Abstract

BackgroundUtilizing the graphite anode and activated carbon cathode to construct dual carbon lithium-ion capacitors (DC-LICs) is recently attracted much attention owing to their cost-effectiveness, enlarged operating voltage, high safety, etc. Despite these merits mentioned above, the kinetic mismatch and imbalance capacity among the electrodes restricts the rate capability and energy density, respectively. MethodsHerein, the high mass-loading (9 mg/cm2) and flexible electrodes composed of hydrogel-derived hierarchical porous activated carbon (HHPAC) are prepared by mechanically blending, repeatedly calendared, and completely dried at 130℃. The resulting free-standing sheets were adopted as electrodes for DC-LICs. Significant findingsBenefiting from the distinctive textural properties (e.g., graphitic layers, multi-porosity, and huge specific surface area of 2,012 m2/g), the energy storage mechanisms of HHPAC anodes simultaneously follow the intercalation and adsorption phenomena, which were confirmed by electrochemical and micro-Raman identifications. Moreover, an additional capacitive contribution (∼31%) and voltage delay of 64 mV are reflected at 5 mV/sec, as evidenced using cyclic voltammetry. Consequently, the DC-LICs assembled with pre-lithiated HHPAC anode and HHPAC cathode exhibited outstanding rate performances (39.7 mAh/g at 0.1 mA/cm2 and 20.3 mAh/g at 10 mA/cm2) and comparable cyclability (81% of retention after 1,400 cycles at 1 mA/cm2), revealing that our HHPAC materials are promising for serving as anode and cathode in DC-LICs.