Ultrathin graphene layer activated dendritic α-Fe2O3 for high performance asymmetric supercapacitors

Poor electronic conductivity is one of the main obstacles that limit the supercapacitive performance of alpha-Fe2O3. Herein, we report an ultrathin graphene layer activation strategy for significantly boosting the electrochemical performance of electrode materials. The alpha-Fe2O3 @C still retains the alpha-Fe2O3 original dendritic architectural structure, which can provide a more effective contact between electrode and electrolyte ions. Meanwhile, the graphene layer simultaneously improves Li+ diffusion and electronic conductivity, thus leading to a greatly enhanced electrochemical performance with a high specific capacitance of 443.2 F g(-1), which is almost double the capacitance of alpha-Fe2O3 without the graphene layer. More importantly, the resultant graphene layer greatly increases the stability of dendritic alpha-Fe2O3 in electrochemical cycle testing. The asymmetric supercapacitor based on a CNT-COOH anode and graphene layer-activated dendritic alpha-Fe2O3 cathode can achieve a high energy density of 77 W h Kg(-1) at a power density of 1380 W kg(-1). Our work provides a simple, novel and effective strategy to significantly enhance the electrochemical performance of alpha-Fe2O3. (C) 2018 Elsevier B.V. All rights reserved.