关键词: 气体扩散层, 装配压力, 质子交换膜燃料电池, 性能

Abstract:

Proton exchange membrane fuel cell (PEMFC) has the advantages of low noise, high power density, and zero emission. It is widely used in ships, automobiles, aviation and other fields. PEMFC is composed of bipolar plate (BP), gas diffusion layer (GDL), catalytic layer (CL) and proton exchange membrane (PEM). GDL has a supporting catalytic layer and proton exchange membrane, which provides gas diffusion for the reaction and a channel for the reaction to produce water, and transmits the anodic oxidation reaction. In the assembly of fuel cells, a certain assembly pressure is required to ensure air-tightness and effective conductivity. The assembly pressure will cause the GDL deformation and the loss of hydrophobic materials; however, the assembly pressure can improve the durability of the battery. Too small assembly pressure will lead to insufficient battery sealing, high contact resistance and other undesirable results. Larger assembly pressure can improve the hydrogen utilization rate and ensure the stable operation of the battery as the assembly pressure increases, Liquid water accumulates more; excessive assembly pressure leads to reduced porosity and lower reaction rate, and even damage of membrane electrode assembly (MEA). Therefore, there is an optimal assembly pressure to obtain lower contact resistance when compressing GDL. At the same time, it has a relatively high porosity. Scholars at home and abroad have mainly studied the effect of GDL deformation on the battery performance, but the exploration of fuel cells with different flow channel widths is not clear. This paper uses the finite element method to establish a single flow. Three-dimensional model of the PEMFC channel has been studied, and the GDL thickness changes and their impacts on the pores under different assembly pressures and three kinds of flow channel to rib ratios (the channel and rib width ratios of 3:2, 1:1, 2:3) were investigated. The results show that: (1) GDL deformation increased with the increases of the ratio of flow channel to rib width and assembly pressure, but the rate of change gradually slowed down. (2) Under the ribs,the porosity of GDL decreased with the increase of assembly pressure, and the decreased change rate continued to be accelerated; under the same assembly pressure, the greater the ratio of channel to rib width, the more significant the porosity change. (3) Conductivity increased with the increase of assembly pressure, and the rate of change was also accelerated with the increase of assembly pressure; under the same assembly pressure, the greater the ratio of the flow channel to the rib width, the greater the electrical conductivity. When the ratio of channel to rib width was 3:2, there was an intersection point at 1.5 ~ 2.0 MPa. According to the balanced relationship between porosity and conductivity, the optimal assembly pressure may be in this interval, which needs to be further verified.

Key words: gas diffusion layer, assembly pressure, proton exchange membrane fuel cell, performance