PNNL

Abstract

To improve the performance of Na-beta batteries at intermediate temperatures (=200°C) where much improved cyclability and reduced degradation can be achieved, there is a need to lower the resistance/polarization coming from BASEs while maintaining good strength. In this paper, the concept of a duplex BASE consisting of a thn dense electrolyte and a porous support was proposed as a solution to achieve low area-specific resistance while maintaining good mechanical strength. The effects of various factors including porosity, composition, and the homogeneity of ingredients on the flexural strength of duplex BASEs were examined. In summary, lower porosity, higher YSZ content in the structure, and the attrition milling of powders resulted in improved strength. The area-specific resistance measurement exhibited that the resistance of duplex BASEs was mainly originated from a dense layer. Overall, the maximum strength of 260 MPa and the ASR value of 0.31 ??cm2 (at 350°C) was achieved from a duplex BASE consisting of a 50 µm thick dense layer (Al2O3: YSZ = 7:3 in volume) and a 500 µm thick porous support (Al2O3: YSZ = 4:6 in volume with 19% open porosity). The effects of various factors on the properties of duplex BASEs will be explained in details.