Development of Compact and High-Performance Fuel Cell Stack

Abstract

Toyota Motor Corporation (TMC) has been developing fuel cell (FC) technology since 1992, and finally “MIRAI” was launched in 15 th Dec. 2014. An important step was achieved with the release of the “FCHV-adv” in 2008. It established major improvements in efficiency, driving range, durability, and cold start capability. However, enhancing performance and further reductions in size and cost are required to facilitate the commercial widespread adoption of fuel cell vehicles (FCVs). TMC met these challenges by developing the world's first FC stack without a humidifying system. This was achieved by the development of an innovative cell flow field structure and membrane electrode assembly (MEA), enabling a compact and high-performance FC stack. Other cost reduction measures incorporated by the FC stack include reducing the amount of platinum in the catalyst by two-thirds and adopting a carbon nano-coating for the separator surface treatment.In the newly developed humidifier-less system, water management in each cell plays a key role in enhancing the performance. This requires measures to ensure proton conductivity and restrict the inhibition of gas diffusion.The new FC stack improves the removal of water and gas diffusion by adopting a newly developed three-dimensional (3D) fine-mesh flow field at the cathode. In addition, precision stamping was adopted for the anode to create an integrated fine-pitch channel flow field with hydrogen flow on the front-side and coolant flow on the back-side. This counter-flow configuration improves the water balance inside each cell and allows humidifier-less operation by enabling self-humidification using generated water alone.