Performance comparison of portable direct methanol fuel cell mini-stacks based on a low-cost fluorine-free polymer electrolyte and Nafion membrane

• Published in: Electrochimica acta Vol. 55; no. 20; pp. 6022 - 6027
• Main Authors: Baglio, V., Stassi, A., Modica, E., Antonucci, V., Aricò, A.S., Caracino, P., Ballabio, O., Colombo, M., Kopnin, E.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2010; Elsevier
• Subjects: Accumulators; Applied sciences; Backbone; Collectors; Direct methanol fuel cells; Electrolytes; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fluorine-free membrane; Fuel cells; Membranes; Methyl alcohol; Mini-stack; Passive mode; Portability; Proton exchange membrane; Direct methanol fuel cells; Proton exchange membrane; Passive mode; Mini-stack; Fluorine-free membrane; Ionomer; Graft copolymer; Polymer solid electrolyte; Alcohol fuel cells; Ethylene oxide copolymer; Sulfonate copolymer; Ethylene oxide polymer; Tetrafluoroethylene copolymer; Styrenesulfonate copolymer; Cation exchange membrane; Portable equipment; Comparative study; Methanol; Electrochemical impedance spectroscopy
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2010.05.059

A low-cost fluorine-free proton conducting polymer electrolyte was investigated for application in direct methanol fuel cell (DMFC) mini-stacks. The membrane consisted of a sulfonated polystyrene grafted onto a polyethylene backbone. DMFC operating conditions specifically addressing portable applications, i.e. passive mode, air breathing, high methanol concentration, room temperature, were selected. The device consisted of a passive DMFC monopolar three-cell stack. Two designs for flow-fields/current collectors based on open-flow or grid-like geometry were investigated. An optimization of the mini-stack structure was necessary to improve utilization of the fluorine-free membrane. Titanium-grid current collectors with proper mechanical stiffness allowed a significant increase of the performance by reducing contact resistance even in the case of significant swelling. A single cell maximum power density of about 18 mW cm −2 was achieved with the fluorine-free membrane at room temperature under passive mode. As a comparison, the performance obtained with Nafion 117 membrane and Ti grids was 31 mW cm −2. Despite the lower performance, the fluorine-free membrane showed good characteristics for application in portable DMFCs especially with regard to the perspectives of significant cost reduction.