Boosting the energy density of supercapacitors by designing both hollow NiO nanoparticles/nitrogen-doped carbon cathode and nitrogen-doped carbon anode from the same precursor

Abstract

• The hollow NiO/NC was designed based on the Kirkendall effect. • 2. The pure NC with hollow structure was prepared using the same precursor. • 3. DFT calculations prove that NiO/NC and NC have excellent electrochemical performance. • 4. High-energy–density asymmetric supercapacitor of 40.2 Wh kg −1 was achieved. Designing the transition metal oxide-based electrode with hollow nanostructure is of great importance for high-performance supercapacitors. Here, the hollow NiO encapsulated in a nitrogen-doped carbon matrix (NiO/NC) is synthesized by using the precursor of Ni-based metal–organic complex based on the Kirkendall effect. With the same precursor, the hollow NC is obtained by removing the Ni element through an acid etching method. Density functional theory (DFT) calculations convince that both hollow NiO/NC and NC have high electrical conductivity and adsorption energy for OH – , demonstrating their high practicability for supercapacitor applications. In a three-electrode system, the NiO/NC sample prepared under 700 °C displays a high specific capacitance (1026 F g −1 at 1 A g −1 ) and excellent cycle stability (80.2% capacity retention over 8000 cycles). Importantly, a high energy density of 40.2 Wh kg −1 was achieved based on the asymmetric supercapacitor assembled with NiO/NC cathode and NC anode. This work provides new insights on designing high-performance electrode materials to boost supercapacitor performance using the same precursor.