Studies On The Preparation And Performance Of Side-chain SPEAK Cation Exchange Membranes For Vanadium Battery

As one of the large scale energy storage technologies, vanadium redox flow battery (VRB) has received wide attention due to its attractive advantages such as it’s long life, flexible design, deep-discharge capacity and environment-friendliness. Ion exchange membrane plays an important role in the development of VRB. In this thesis, a series of side-chain sulfonated poly(aryl ether ketone)s with different structures were synthesized and studied in vanadium redox flow battery.MPAEK copolymers were prepared via nucleophilic polycondensation reaction by adjusting the ratio of the bisphenol monomer and bisfluorene monomer, and then they were converted into HPAEK. With several sulfonated reagent, including 1,3-propane-sultone, SDFK,4-phenolsulfonic acid sodium, at last SPAEK, SPAEK50 and CSPAEK cation exchange membranes were obtained. Structures of these synthesized sulfonated copolymers were confirmed by 1H-NMR and FT-IR. And their microstructures were investigated by transmission electron microscopy. Mechanical properties, oxidative stabilities of these membranes were also systematically studied. It turned out that these performance was suitable for the requirements of ion exchange membranes.The water uptake, swelling ratio and IEC were increased along with longer reaction time or the ratio of sulfonated monomer. H+ permeability of SPAEK and SPAEK50 mem-branes was studied. It showed that the value of IEC was helpful to H+ permeability. The proton conductivity and VO2+ permeability of SPAEK, CSPAEK membranes were investigated and compared to Nafion117. A lower relative selectivity and proton con-ductivity than that of Nafion117 were also observed. However, the result demonstrated that the CSPAEK membranes had good performance. The proton conductivity of CSPAEK70-6 reached 7.91×10-2s/cm and the VO2+ permeability was far below 6.04×10-6 cm2/min. Then SPAEK and CSPAEK membranes were used as the separator in a single cell vanadium redox flow battery. At a current density of 20 mA/cm2, the SPAEK-70, CSPAEK50-4 membranes showed the same OCV duration as Nafion117. The VRB containing the CSPAEK70-5 membrane exhibited similar coulombic efficiency compared to the VRB using Nafion117. Better vanadium ion selectivity of these membranes has led to a smaller capacity loss. Novel side-chain sulfonated poly(aryl ether ketone)s have good electrochemical performance.