Latest FCV Development in Nissan - Challenges for Durability and Cost

摘要

CO_2 emissions reduction from automobiles is quite important from global warming and energy security view points. Nissan has been developing both electric vehicles (EVs) and fuel cell vehicles (FCVs) as zero emission vehicles for CO_2 emissions reduction. Research and development work on Nissan FCVs has been under way since 1996. The main issues that must be addressed to commercialize FCVs include: (1) preventing performance decay, (2) developing technologies for reducing costs, (3) increasing power density and (4) improving subzero start-up capability. Fundamental research activities undertaken to resolve these issues have elucidated various phenomena such as the mass transportation and degradation mechanisms in the membrane electrode assembly (MEA) and corrosion on metal bipolar plates. These activities have accumulated the following technologies and results: (1) method of estimating performance decay, (2) surface treatment technology for corrosion-proofing metal bipolar plates, (3) verification of improved subzero start-up capability and (4) MEA specifications for high current density operation with low cathode humidity and reduced cost. These technologies have been incorporated in a Nissan fuel cell stack 2008 model that achieves a power density of 1.9 kW/L (130 kW/68 L) and a lower cost by halving the amount of Pt catalyst compared with the previous stack model. The performance and durability of the new stack are close to satisfying the requirements for real-world use. However, new stack cost needs additional reduction. One effective approach to reducing the cost is to lower the amount of Pt catalysts used by utilizing Pt more effectively. Toward that end, it is important to further analyze the reaction and physical transport mechanisms taking place at the electrode catalyst layer. This paper presents the results achieved to date and describes various activities under way to address the two major issues, namely performance decay and cost reduction, among the four main issues mentioned above.