Published April 7, 2022 | Version v1
Journal article Open

Sulfonated NbS2-based proton-exchange membranes for vanadium redox flow batteries

Authors/Creators

  • 1. BeDimensional S.p.A, Lungotorrente Secca, 30R 16163 Genoa, Italy
  • 2. Department of Material Science and Engineering, Uppsala University, Box 534, 75103 Uppsala, Sweden
  • 3. Graphene Labs, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy
  • 4. Department of Chemical Engineering, Semnan University, Semnan, Iran
  • 5. Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic

Description

In this work, novel proton-exchange membranes (PEMs) based on sulfonated poly(ether ether ketone) (SPEEK) and two-dimensional (2D) sulfonated niobium disulphide (S-NbS2) nanoflakes are synthesized by a solution-casting method and used in vanadium redox flow batteries (VRFBs). The NbS2 nanoflakes are produced by liquid-phase exfoliation of their bulk counterpart and chemically functionalized with terminal sulfonate groups to improve dimensional and chemical stabilities, proton conductivity (σ) and fuel barrier properties of the as-produced membranes. The addition of S-NbS2 nanoflakes to SPEEK decreases the vanadium ion permeability from 5.42 × 10−7 to 2.34 × 10−7 cm2 min−1. Meanwhile, it increases the membrane σ and selectivity up to 94.35 mS cm−2 and 40.32 × 104 S min cm−3, respectively. The cell assembled with the optimized membrane incorporating 2.5 wt% of S-NbS2 nanoflakes (SPEEK:2.5% S-NbS2) exhibits high efficiency metrics, i.e., coulombic efficiency between 98.7 and 99.0%, voltage efficiency between 90.2 and 73.2% and energy efficiency between 89.3 and 72.8% within the current density range of 100–300 mA cm−2, delivering a maximum power density of 0.83 W cm−2 at a current density of 870 mA cm−2. The SPEEK:2.5% S-NbS2 membrane-based VRFBs show a stable behavior over 200 cycles at 200 mA cm−2. This study opens up an effective avenue for the production of advanced SPEEK-based membranes for VRFBs.

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Additional details

Funding

European Commission
GrapheneCore3 - Graphene Flagship Core Project 3 881603
European Commission
ULTIMATE - Bottom-Up generation of atomicalLy precise syntheTIc 2D MATerials for high performance in energy and Electronic applications – A multi-site innovative training action 813036
European Commission
SENSIBAT - Cell-integrated SENSIing functionalities for smart BATtery systems with improved performance and safety 957273