Assembly of flexible CoMoO₄ @NiMoO₄ ·xH₂O and Fe₂O₃ electrodes for solid-state asymmetric supercapacitors

In this work, CoMoO₄ @NiMoO₄ ·xH₂O core-shell heterostructure electrode is directly grown on carbon fabric (CF) via a feasible hydrothermal procedure with CoMoO₄ nanowires (NWs) as the core and NiMoO₄ nanosheets (NSs) as the shell. This core-shell heterostructure could provide fast ion and electron transfer, a large number of active sites, and good strain accommodation. As a result, the CoMoO₄ @NiMoO₄ ·xH₂O electrode yields high-capacitance performance with a high specific capacitance of 1582 F g^-1, good cycling stability with the capacitance retention of 97.1% after 3000 cycles and good rate capability. The electrode also shows excellent mechanical flexibility. Also, a flexible Fe₂O₃ nanorods/CF electrode with enhanced electrochemical performance was prepared. A solid-state asymmetric supercapacitor device is successfully fabricated by using flexible CoMoO₄ @NiMoO₄ ·xH₂O as the positive electrode and Fe₂O₃ as the negative electrode. The asymmetric supercapacitor with a maximum voltage of 1.6 V demonstrates high specific energy (41.8 Wh kg^-1 at 700 W kg^-1), high power density (12000 W kg^-1 at 26.7 Wh k^-1), and excellent cycle ability with the capacitance retention of 89.3% after 5000 cycles (at the current density of 3A g^-1).