Partially fluorinated sulfonated poly(arylene ether) (SFPAE) copolymers were investigated as chemically stable proton exchange membranes for application in vanadium redox flow batteries (VRFB). The membranes' proton conductivity and vanadium ion permeability were quantified and correlated to other membrane properties such as water uptake and tensile modulus to provide insight into the tradeoffs in the design of new membranes for flow battery applications. The SFPAE-1.8 sample with optimized proton conductivity to vanadium permeability selectivity was selected for evaluation in a VRFB device and compared to the performance of a cell with a NAFION 1 N212 membrane. The VRFB cell with a SFPAE-1.8 membrane had higher coulombic efficiency, voltage efficiency, and energy efficiency compared to a VRFB with a N212 membrane under all tested current densities. The capacity fade of a VRFB with the SFPAE-1.8 membrane was 1.1 mA h per cycle, which was about 7 times lower than the fade experienced for a VRFB with a N212 membrane. The performance characteristics of the device could be correlated directly to the membrane properties and this work demonstrates our progress towards high-performance, low-cost, long-lifetime ion exchange membranes for electrochemical energy storage devices.

No abstract

No abstract

Executive SummaryThe objective of this project is to investigate and develop novel, mechanically activated, nanoscale Li 3 N-based and LiBH 4 -based materials that are able to store and release ~10 wt% hydrogen at temperatures near 100°C with a plateau hydrogen pressure of less than 10 bar. Four (4) material systems have been investigated in the course of this project in order to achieve the project objective. These 4 systems are (i) LiNH 2 +LiH, (ii) LiNH 2 +MgH 2 , (iii) LiBH 4 , and (iv) LiBH 4 +MgH 2 . The key findings we have obtained from these 4 systems are summarized below. The thermodynamic driving forces for LiNH 2 +LiH and LiBH 4 systems are not adequate to enable H 2 release at temperatures < 100 o C.  Hydrogen release in the solid state for all of the four systems is controlled by diffusion, and thus is a slow process.  LiNH 2 +MgH 2 and LiBH 4 +MgH 2 systems, although possessing proper thermodynamic driving forces to allow for H 2 release at temperatures < 100 o C, have sluggish reaction kinetics because of their diffusion-controlled rate-limiting steps.

not Available.