Cross-linked NiCo2O4 nanosheets with low crystallinity and rich oxygen vacancies for asymmetric supercapacitors

Abstract The electrochemical performance of NiCo2O4 currently still faces inherently limited active sites and less available surface areas, hindering its application as the pseudocapacitive electrode in supercapacitors. Accordingly, the cross-linked NiCo2O4 nanosheets with low crystallinity and rich oxygen vacancies on nickel foam (Pd–NCO/NF) by introducing noble metal palladium (Pd2+) has been fabricated. The results show that the lattice orientation of NiCo2O4 nanoparticles is disordered by Pd doping, leading to a decrease in crystallinity. In addition, low crystallinity with a large number of lattice boundaries results in the high electrochemical activity with 2484.4 F g−1. At high current density of 10 A g−1, the capacitance retention could remain 95% after 8000 cycles. An asymmetric supercapacitor of Pd–NCO/NF//activated polyaniline derived carbon (APDC) demonstrates high energy density of 47.5 W h kg−1 at 425.4 W kg−1 and promotes excellent cycle stability, with a capacity retention rate of 86% after 10,000 cycles.