Stamen-petal-like CeO2/NiMn layered double hydroxides composite for high-rate-performance supercapacitor

Layered double hydroxides are widely used as electroactive materials for supercapacitors. However, they exhibit poor rate performances at high current densities. To improve the rate performance of layered double hydroxides, a stamen-petal-like CeO2/NiMn layered double hydroxides composite is synthesized successfully by a one-step hydrothermal method. During the hydrothermal reaction, stamen-like CeO2 precipitates first, followed by the crystallization of petal-like NiMn layered double hydroxides sheets around the CeO2 stamen-like particles. By adjusting the amount of Ce(NO3)(3) in the reaction mixture, an optimal composite electrode is obtained, which exhibits maximum specific capacities of 1956.0 F g(-1) (1173.6C g(-1)) and 1261.4 F g(-1) (756.8C g(-1)) at 1 Ag-1 and 20 A g(-1), respectively, and a much better rate performance compared with the traditional NiMn layered double hydroxides and CeO2 composite. A hybrid capacitor assembled using the optimal composite and activated carbon shows a high specific capacitance of 145.7 F g(-1), and a capacitance retention rate of 91.9% after 5000 cycles at 10 A g(-1). The maximum energy density is 51.8 Wh kg(-1) at a power density of 809 W kg(-1). The excellent performance is attributed to the special petal-like structure of the layered double hydroxides sheets, which provides a higher specific surface area and abundant pathways for ion transport. In addition, the CeO2 particles among the petal-like layered double hydroxides sheets effectively reduce the internal electrochemical resistance of the composite electrode, thereby according a high rate performance. (C) 2019 Elsevier B.V. All rights reserved.