Rational Assembly of CoAl-Layered Double Hydroxide on Reduced Graphene Oxide with Enhanced Electrochemical Performance for Energy Storage

In this paper, we designed and synthesized composites of CoAl-layered double hydroxide on reduced graphene oxide (CoAl-LDH@rGO/NF) via a facile approach. The Co-Al layered double hydroxide (CoAl-LDH) nanosheets were grown onto the skeleton of reduced graphene oxide on Ni foam (rGO/NF). The as-synthesized CoAl-LDH@rGO/NF composites exhibited a superior electrochemical behavior, attributed to the coupling effect of homogeneous CoAl-LDH nanosheets and high conductivity of rGO. In addition, the different morphologies of the CoAl-LDH@rGO/NF composites can be controlled by adjusting the amount of NH4F. The optimum electrochemical performance of the CoAl-LDH@rGO/NF hybrid electrode was obtained when the amount of NH4F was 6 mmol. The largest specific capacitance of 1671.4 F g(-1) (1 A g(-1)) and the ultra-high cycling performance with 97 cvo retention of the original value were achieved even after 5000 charge-discharge cycles. A remarkable energy density value of 41.3 Wh kg(-1) at a power density of 408.9 Wkg(-1) was achieved in the asymmetric supercapacitor (ASC) using CoAl-LDH@rGO-6/NF and activated carbon (AC) for positive and negative materials. Furthermore, the ASC retained 100% of its original energy density value even after 5000 cycles. In addition, a design method for preparing high performance electrode materials with ideal morphology is proposed in this paper, which might be helpful to the future study of morphology and electrochemical properties.