Effect of Different Additives on the Electrochemical Behaviour of Nickel Hydroxide Electrodes employed in Batteries

MARIELA GISELA ORTIZ; SILVIA GRACIELA REAL; ELIDA BEATRIZ CASTRO

Lausanne

Congreso; 65th Annual Meeting of the International Society of Electrochemistry; 2014

International Society of Electrochemistry

Nickel hydroxide is widely used as the activematerial in positive electrodes in most nickel-based rechargeable alkalinebatteries. The theoretical capacity of nickel hydroxide is 289 mAhg-1.The capacity of these batteries depends on the specific capacity of thepositive electrode and the utilization of the active material because of thepositive electrode capacity limitation.The poor conductivity of active material requires theaddition of some additives to increase conductivity and, additionally, toincrease the oxygen evolution potential, the charge efficiency and to inhibitthe development of γ-NIOOH phase. Many studies have been published on nickelhydroxide with different additives to obtain optimum performance; for example:cobalt [1-2], carbonaceous materials [3], calcium [3], zinc [2] andnanomaterials [4]. In this work, we have studiedthe electrochemical behaviour of nickel hydroxide electrodes containingadditives as: cobalt (by electroless technique), nanosized Ni(OH)2  (by direct mix with active material) andMWCNTs (incorporated to active material during hydrothermal synthesis). Their electrochemicalcharacterization was investigated by using cyclic voltammetry, charge-dischargecycling, and electrochemical impedance spectroscopy (EIS) techniques. The experimentalEIS data are used to identify the model parameters by fitting the theoreticalimpedance function; this was derived from the physicochemical model based onthe theory of porous electrodes with the charge/discharge processes occurringat the active material/electrolyte interface [5]. The results are found to beuseful to determine the key factors responsible of the electrochemical performanceof nickel hydroxide electrodes.