A high-performance supercapacitor/battery hybrid incorporating templated mesoporous electrodes

A supercapacitor/battery hybrid was fabricated using a mesoporous Ni/Ni(OH)(2) positive electrode and a mesoporous Pd negative electrode, both fabricated by electrodeposition of the metal within the hexagonal phase of a liquid crystalline template. Because we are predominantly interested in the performance of the Ni/Ni(OH)(2) electrode, we have designed the device such that performance is positive electrode limited. Use of Ni(OH)(2) rather than NiO allows us to derive a significant proportion of the capacity from bulk redox processes and the designed porous electrode structure allows us to access this capacity very rapidly. Cyclic voltammetry and potential step experiments show that we are able to deliver 222 mC cm(-2) or 166 mA h g(-1) (of Ni electrode) in 50 ms at a mean discharge voltage of 1.18 V using an aqueous electrolyte. This translates into energy and power densities of 706 kJ kg(-1) and 14.1 MW kg(-1), respectively, for the Ni/Ni(OH)(2) electrode. Furthermore, device capacity has been shown to resist decay and actually increase by 10% over 15,000 cycles. (C) 2003 The Electrochemical Society.