A novel nanostructured mesoporous CoxNi1-x layered double hydroxides (CoxNi1-x LDHs), which both Co(CH)(2) and Ni(CH)(2) exhibit, has been successfully synthesized by a chemical co-precipitation route using polyethylene glycol as the structure-directing reagent. Structural and morphological characterizations were performed using powder X-ray diffraction (XRD) and held emission scanning electron microscopy (FESEM). The component and thermal stability of the sample were measured by energy dispersed X-ray spectrometry (EDS), Fr-IR and thermal analyses, including thermogravimetry (TG) and differential thermal analysis (DTA). Cyclic voltarnmogram and galvanostatic charge-discharge testified that the CoxNi1-x LDH has a specific capacitance of 1809 F g(-1) at a current density of 1 Ag-1 and remains at about 90.2% of the initial value after 1000 cycles at a current density of 10 A g(-1). The relationship between the chemical composition and the capacitance is discussed. (C) 2008 Elsevier Ltd. All rights reserved.