Nickel-cobalt double oxides with rich oxygen vacancies by B-doping for asymmetric supercapacitors with high energy densities

Boron-doped NiCo2O4 (B-NiCo2O4) nanoarchitectures with rich oxygen vacancies have been rationally designed and synthesized on carbon fabrics via a conventional chemical reduction strategy. The B doping successfully realizes the introduction of oxygen vacancies, effectively accelerates ion and electron transport, increases the redox reactive sites, which endow the B-NiCo2O4 electrode with high specific capacity (799.9 C g−1 at 1 A g−1), outstanding rate capability (maintained about 75.1% at 20 A g−1) and impressive cyclic stability (about 94.7% retention of the initial capacity after 5000 cycles). The corresponding asymmetric supercapacitor assembled directly with B-NiCo2O4 electrodes exhibits a high energy density (77.7 Wh kg−1 at 2890.8 W kg−1) and a long lifespan (91% retention ratio after 5000 cycles). These remarkable properties indicate that the doping of hybrid atoms and the construction of defect engineering will provide a favorable reference for the performance promotion of the next-generation of energy storage devices.