Electrodeposition synthesis of high performance MoO3-x@Ni-Co layered double hydroxide hierarchical nanorod arrays for flexible solid-state supercapacitors

Abstract As a pseudocapacitive material, layered MoO3 has attracted extensive attention for its excellent ion storage capacity. However, the low conductivity and irreversible phase transition make its capacity decrease rapidly during the charging and discharging process, which seriously limits the application in the field of supercapacitors. This study obtains the hierarchical MoO3-x@NCLDH with oxygen vacancy by using the MoO3 nanorods array as the matrix, wrapping the Ni-Co layered double hydroxide (NCLDH) by electrodeposition method. The MoO3-x@NCLDH-15 electrode with the electrodeposition time of 15 minutes shows a capacitance of 3.49 F cm-2 at the current density of 5 mA cm−2 and capacitance retention of 94.5% after 3000 cycles in the neutral electrolyte. The prepared symmetric flexible solid-state supercapacitor with MoO3-x@NCLDH-15 as electrode material exhibits good flexibility and the maximum energy density of 0.047 mWh cm−2 at 0.865 mW cm−2 power density. On the one hand, the hierarchical structure changes the microenvironments of the electrode surface, which can provide more responsive sites for pseudocapacitance reaction and shorten the ion transportation path to accelerate the reaction kinetics. On the other hand, NCLDH nanosheets tightly wrapped on the surface of MoO3 nanorods array slow down the structural collapse in the potassium ion removal process. Besides, the introduction of oxygen vacancies improves the electrical conductivity and structural stability of MoO3. Therefore, our work provides a new strategy for constructing flexible electrode materials with high electrochemical performance.