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

Abstract

• The design of hierarchical structure can effectively improve the electrochemical performance of MoO 3. • Oxygen defect production can effectively improve the conductivity of MoO 3 . • MoO 3-x @NCLDH-15 symmetric flexible SSCs exhibits high energy density and power density. As a pseudocapacitive material, layered MoO 3 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 MoO 3-x @NCLDH with oxygen vacancy by using the MoO 3 nanorods array as the matrix, wrapping the Ni-Co layered double hydroxide (NCLDH) by electrodeposition method. The MoO 3-x @NCLDH-15 electrode with the electrodeposition time of 15 min 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 MoO 3-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 MoO 3 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 MoO 3 . Therefore, our work provides a new strategy for constructing flexible electrode materials with high electrochemical performance.