TiO2 Containing Hybrid Composite Polymer Membranes for Vanadium Redox Flow Batteries

Abstract

In recent years, vanadium redox flow batteries (VRFB) have captured immense attraction in electrochemical energy storage systems due to their long cycle life, flexibility, high-energy efficiency, time, and reliability. In VRFB, polymer membranes play a significant role in transporting protons for current transmission and act as barriers between positive and negative electrodes/electrolytes. Commercial polymer membranes (such as Nafion) are the widely used IEM in VRFBs due to their outstanding chemical stability and proton conductivity. However, the membrane cost and increased vanadium ions permeability limit its commercial application. Therefore, various modified perfluorinated and non-perfluorinated membranes have been developed. This comprehensive review primarily focuses on recent developments of hybrid polymer composite membranes with inorganic TiO2 nanofillers for VRFB applications. Hence, various fabrications are performed in the membrane with TiO2 to alter their physicochemical properties for attaining perfect IEM. Additionally, embedding the -SO3H groups by sulfonation on the nanofiller surface enhances membrane proton conductivity and mechanical strength. Incorporating TiO2 and modified TiO2 (sTiO2, and organic silica modified TiO2) into Nafion and other non-perfluorinated membranes (sPEEK and sPI) has effectively influenced the polymer membrane properties for better VRFB performances. This review provides an overall spotlight on the impact of TiO2-based nanofillers in polymer matrix for VRFB applications.

Sulfonated Poly(ether Ether Ketone)/Sulfonated Covalent Organic Framework Composite Membranes with Enhanced Performance for Application in Vanadium Redox Flow Batteries

“…The non-fluorinated alternatives, with low cost and high efficiency, have attracted considerable attention in recent years . Sulfonated poly­(ether ether ketone) (SPEEK) is considered one of the most promising proton-conductive materials owing to its good membrane-forming properties, excellent mechanical properties, and low cost. − Although the proton conductivity of SPEEK membranes enhances with an increase in the sulfonation degree (SD), the dimensional stability and mechanical properties of the membranes decrease. In addition, an increased SD generally results in a high vanadium ion permeability of the membrane, which degrades the electrochemical performance of the VRFBs. , …”

Deciphering the role of 2D graphene oxide nanofillers in polymer membranes for vanadium redox flow batteries

“…105,106 One of the excellent options for developing high-performance IEM for VRFB systems is to incorporate inorganic additives as a nanoller into the polymer matrix. 10,[107][108][109][110][111][112] This review paper explores the impact of graphene oxide (GO) as a nanoller for different polymer membranes in relation to their performance in VRFB. The review has been categorized into two broader distinct groups, taking into consideration the polymers used as well as the features of GO (non-modied and modied GO).…”

“…8,9 One of the most challenging issues associated with the use of fossil fuels pertains to their detrimental impact on the environment via pollution. 3,10,11 The extraction and consumption of fossil fuels result in several forms of environmental contamination, including air pollution, water pollution, and soil pollution because of highly hazardous emissions. [12][13][14][15][16][17][18] Scientists and scholars worldwide are actively investigating alternative and environmentally sustainable energy sources as potential substitutes for fossil fuels, to address the associated challenges and consequences.…”

“…105,106 One of the excellent options for developing high-performance IEM for VRFB systems is to incorporate inorganic additives as a nanofiller into the polymer matrix. 10,107–112…”

3D Carbon Nanonetwork Coated Composite Electrode with Multi-Heteroatom Doping for High-Rate Vanadium Redox Flow Batteries

“…However, the original GFs usually present poor electrochemical activity and sluggish kinetics of electron and ion transport, largely restricting the rate performance and cycling stability of VRFBs. To enhance the electrochemical performance of GFs, various methods, including surface functional groups [ 23 , 24 , 25 , 26 , 27 , 28 ], metal and metallic oxides deposition [ 29 , 30 , 31 ], element doping [ 32 , 33 , 34 ], and functional carbon nanomaterial [ 35 , 36 , 37 ] have been applied to modify the composite electrodes for VRFBs. Firstly, the surface functionalization, such as acid treatment, heat treatment electrochemical oxidation, and oxygen plasma treatment, mainly introduce oxygen-containing functional groups on the electrode surface, and the abundant oxygen-containing functional groups can effectively improve the hydrophily of GFs [ 38 , 39 ], which prompts the sufficient wettability between electrolyte and GFs, and enhances the redox reaction of vanadium ions.…”