Cobalt Hydroxide as a Capacitor Material: Tuning Its Potential Window

Abstract

Research activities on various supercapacitor materials have grown enormously in recent years. Capacitor studies of Co (OH) 2 over a limited potential window in alkaline electrolytes are reported. A high potential window of a capacitor material is desirable for use in a device. Furthermore, as the specific energy and specific power of a capacitor depend strongly on its voltage, experiments are conducted in the present work to understand the reason for a low potential window for Co (OH) 2 as a capacitor material and also to increase its potential window. Experiments are conducted in NaOH and Na 2 S O 4 electrolytes of various concentrations using electrochemically precipitated Co (OH) 2 on stainless steel current collectors in an aqueous Co (N O3) 2 electrolyte. Based on the potential window, specific capacitance, and specific energy, it is found that 0.05 M NaOH electrolyte is more appropriate for capacitor properties of Co (OH)2 than the rest of the electrolytes studied. Using a Co (OH)2 electrode with a specific mass of 1.0 mg cm-2 in 0.05 M NaOH, a specific capacitance of about 380 F g-1 is obtained with a potential window of 0.85 V at a charge-discharge current density of 10 A g-1 (10 mA cm-2). © 2008 The Electrochemical Society.