LaMnO x Air Diffusion Cathode for Primary Alkali Batteries
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nOx Air Diffusion Cathode for Primary Alkali Batteries M. S. Yazici* TUBITAK Marmara Research Center, Energy Institute, Gebze, 41470 Turkey *e-mail: [email protected] Received July 23, 2019; revised October 24, 2019; accepted December 10, 2019
Abstract—Electrochemical performance of a new type of high-current air cathode is compared to off-theshelf air electrodes (Alupower-A series; Eltech-B; Duracell-C) in 35% KOH solution. LaMnOx (LAM) is made by precipitation method resulting with sub-micron size particles. The electrode is single layer and very resistant to the KOH leakage. Approximately 65 m2 g–1 surface area is favorable for effective catalyst distribution and electrochemical active area utilization. LaMnOx type catalyst-supported electrode performs comparable or better than many of the commercial samples. Electrode shows a voltage drop of less than 200 mV at 150 mA cm–2 current density. Electrode structure does not show any sign of mass transfer limitation up to 250 mA cm–2. Keywords: alkaline, air electrode, cathode, zinc–air DOI: 10.1134/S1023193520080078
INTRODUCTION Metal–air batteries store more energy per unit of weight than any other primary type and maintain constant voltage throughout the discharge period [1]. However, self-discharge, activation process and electrolyte leakage from air electrode limit widespread metal-air battery use at high current applications and require further performance and design improvements. Capability to operate zinc-air cells at high current densities while maintaining acceptable durability can be achieved mainly by designing a state of the art gas diffusion electrode with active air management and enough catalytic activity. Porous electrodes are used for oxygen reduction reaction to achieve much higher current densities. The electrode consists of a composite structure that contains electrocatalyst on a high surface area carbon black and polytetrafluoroethylene (PTFE) binder as a wet proofing agent. Each component contributes the requirements of threephase contact through gas permeation, liquid transfer and electron conduction [2]. A three phase interface is established in the region of the porous electrode between gas, electrolyte and the reactant [3]. The nature of this interface plays a critical role in the electrochemical performance, particularly in the liquid electrolyte systems. In such systems, the reactant gases (air or oxygen) diffuse through a thin electrolyte film that wets portions of the porous electrodes and into the hydrophobic portion of the cathode, and then it reaches a hydrophilic portion containing electrolyte, and oxygen reduction catalyst and an electronically conducting medium. In this region it reacts electro-
chemically on the electrode surface by transfer of electrons. When porous electrode contains an excessive amount of electrolyte, the electrode may “flood” and restrict the transport of gaseous species in the electrolyte phase. To provide an efficient operation of this process, cathode must provide a means allowing an adequate supp
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