(229i) Electrosprayed MnO2 Electrodes for Supercapacitors

The electric double-layer capacitors, also referred to as supercapacitors, represent a group of emerging energy storage technology with the properties filling the gap between rechargeable batteries and classical capacitors. The charge separation in the electric double-layer on the interface of porous electrodes soaked with electrolyte results in the fast energy storage/release (specific power > 10³ W/kg) and extended capacitance of up to hundreds of F/g of electrode material. The specific capacitance of supercapacitors can be further extended by the pseudo-capacitive contribution of faradaic processes taking place on the electrode-electrolyte interface or in the surface layer of the electrode¹. Resulting properties of such systems are beneficially employed in wide range application, e.g., recuperation of breaking energy and delivery of starting energy for electric vehicles.

In our contribution we prepared porous MnO₂ electrodes for supercapacitors using electrospraying of aqueous solution of Mn-based precursor. Manganese was selected for its low costs, environmentally friendly nature and pseudo-capacitive behavior. The electrospraying method enables the direct and homogeneous deposition manganese oxide particles of uniform size in the range of 10-100 nm. Within the study, the electrospraying procedure was optimized with respect to the composition of precursor solution and its flow-rate, operating voltage of electrospray, inter-electrode distance and amount of deposited matter. The post-treatment of the electrode by potentiodynamic cycling in three-electrode arrangement was used to achieve the required MnO₂ layer of porous structure. Subsequently, the electrodes were characterized in a laboratory supercapacitors cell using aqueous solution of Na₂SO₄ as electrolyte. Both symmetric and asymmetric configurations of supercapacitor were tested, the latter one using carbon-based counter electrode. The specific capacitance, resistance and cycle stability of the prepared super-capacitors were measured.

Conway, B.E., V. Birss, and J. Wojtowicz, The role and utilization of pseudocapacitance for energy storage by supercapacitors. Journal of Power Sources 1997, 66 (1–2), p. 1-14.