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Development of ultra-high ion selective composite membranes for all vanadium redox flow battery

Development of ultra-high ion selective composite membranes for all vanadium redox flow battery
Translated Title
바나듐 레독스 플로우 배터리 운용을 위한 뛰어난 이온 선택성을 지닌 복합막 개발
Abdul Aziz
DGIST Authors
Abdul Aziz; Shanmugam, Sangaraju; Kim, Jae Hyeon
Shanmugam, Sangaraju
Kim, Jae Hyeon
Issue Date
Degree Date
2017. 2
Vanadium redox flow batterycomposite membraneNafionvanadium ion crossoverion selectivity바나듐 레독스 플로우 배터리복합막나피온바나듐 이온 크로스오버
The ultra-high proton/vanadium ion selective composite membranes for vanadium redox flow battery (VRB) consisting of ZrO2 nanotubes (ZrNT) with perfluorosulfonic acid (Nafion) and polyoxometalate coupled with a graphene oxide-sulfonated poly(arylene ether ketone) (SPAEK) were designed and fabricated. The main goal of introducing ZrNT and PW-mGO fillers in Nafion and SPAEK membrane are to provide high proton conductivity of the composite membrane as well as to partially block the porous structure of Nafion and SPAEK pristine membranes to reduce the vanadium ion permeability by tortuous pathway effect. The incorporation of zirconium oxide nanotubes in the Nafion matrix exhibited high proton conductivity (95.2 mS cm-1), low vanadiumion permeability (3.2 × 10-9 cm2 min-1) and superior ion selectivity (2.95 × 107 S min cm-3). Similarly, the superior proton conductivity of SPAEK-PW mGO composite membrane exhibits 20-times lower vanadium ion crossover than a pristine Nafion membrane. The fabricated composite membranes, Nafion-ZrNT and SPAEK/PW-mGO were used as an electrolyte membrane for VRB showed low self-discharge rate (open circuit voltage was maintained above 1.3 V after a period of 330, 441 h, respectively) relative to a pristine Nafion membrane (29 h). After 100th charge-discharge cycle, the capacity retention for Nafion-ZrNT and SPAEK/PW-mGO composite membrane exhibits 66 and 78%, respectively, which are much better compared with a Nafion membrane (38%). The high performance of composite membranes can be more obviously observed in the coulombic efficiency, voltage efficiency and energy efficiency of the VRB with Nafion-ZrNT and SPAEK/PW-mGO composite membranes compared with a Nafion membrane at a 40 mA cm-2 current density. The detailed overview are reported in results and discussion part. The improved performance is attributed to the superior proton conductivity, low vanadium permeability and strong chemical stability of Nafion-ZrNT and SPAEK/PW-mGO composite membranes. ⓒ 2017 DGIST
Table Of Contents
I. INTRODUCTION 1-- 1.1 Theoretical background 1-- 1.2 The fundamental of VRFB 2-- 1.3 Problem description and current understanding 3-- 1.4 The development of VRFB technique 5-- 1.4.1 Carbon electrode and its improvement 5-- 1.4.2 Membrane development 5-- Chemical stability 6-- Water transport 7-- Vanadium ion crossover 8-- 1.4.3 Membrane materials for VRFB system 10-- Nafion/filler hybrid membranes 10-- Nafion modification with ion exchange polymer 12-- Non-ion exchange polymer modification 13-- Hydrocarbon polymer 14-- Anion exchange membranes 15-- 1.4.4 Effort for electrolyte improvement 17-- 1.5 Motivation and goal of this dissertation 18-- 1.5.1 Nafion-ZrO2 nanotube composite membrane 19-- 1.5.2 SPAEK/ Polyoxometalate-modified graphene oxide composite membrane 20-- II. EEPERIMENTAL SECTTION 22-- 2.1 Nafion-ZrO2 nanotube composite membrane 22-- 2.1.1 Materials 22-- 2.1.2 Preparation of ZrO2 nanotubes 22-- 2.1.3 Preparation of Nafion-ZrO2 nanotubes composite membrane 22-- 2.2 SPAEK/ Polyoxometalate-modified graphene oxide composite membrane 23-- 2.2.1 Materials 23-- 2.2.2 Synthesis of hydrophilic oligomer 23-- 2.2.3 Synthesis of hydrophobic oligomer 24-- 2.2.4 Synthesis of block copolymer (SPAEK) 24-- 2.2.5 Preparation of graphene oxide 25-- 2.2.6 Preparation of reduced graphene oxide 25-- 2.2.7 Preparation of modified graphene oxide 25-- 2.2.8 Preparation of PW-mGO material 26-- 2.2.9 Preparation of SPAEK/PW-mGO composite membrane 26-- 2.3 Characterization 26-- 2.3.1 Field-emission scanning electron microscope (SEM) 26-- 2.3.2 Field-emission transmission electron microscope (TEM) 26-- 2.3.3 X-ray diffraction (XRD) 27-- 2.3.4 Water uptake, Swelling degree and Ion exchange capacity (IEC) 27-- 2.3.5 Proton conductivity 27-- 2.3.6 Oxidative stability 28-- 2.3.7 Thermal stability 28-- 2.3.8 Measurements of VO2+ permeability and ion selectivity 28-- 2.3.9 Measurements of vanadium flow battery performance 29-- III RESULTS AND DISCUSSION 32-- 3.1 Nafion-ZrO2 nanotube composite membrane 32-- 3.1.1 Characterization of ZrO2 nanotube 32-- 3.1.2 Characterization of Nafion-ZrO2 nanotube composite membrane 34-- 3.1.3 VO2+ permeability and ion selectivity 41-- 3.1.4 Vanadium flow battery performance 43-- 3.2 SPAEK/ Polyoxometalate-modified graphene oxide composite membrane 52-- 3.2.1 Characterization of composite membrane 52-- 3.2.2 VO2+ permeability and ion selectivity 55-- 3.2.3 Vanadium flow battery performance 57-- IV CONCLUSIONS 68-- V REFERENCES 69
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