20 V stack of aqueous supercapacitors with carbon (−), titanium bipolar plates and CNT‐polypyrrole composite (+)

Abstract

Abstract A 20 V stack of 19 supercapacitors was fabricated from titanium bipolar plates (150 × 150 × 0.1 mm 3 ) coated on each side with carbon nanotubes and polypyrrole composite (+) and pigment carbon black (−), and microporous polymeric separators containing aqueous KCl. Internal sealing of each cell in the stack was achieved by placing a silicone rubber washer between neighboring bipolar plates. The stack was tested by high voltage cyclic voltammetry, galvanostatic charging and discharging, and electrochemical impedance spectroscopy. It approached 25 kW/kg in maximum specific power and 3.64 Wh/kg in specific energy. Performance of the stack through intermittent charging‐discharging tests in a storage period of 10 months (still ongoing) remained fairly stable. For example, it exhibited almost zero decay in capacitance after 1000 continuous galvanostatic charging‐discharging cycles in the first month of storage (10 V), and less than 6% loss in the seventh month (19 V). © 2011 American Institute of Chemical Engineers AIChE J, 2012