Dataset: A Sustainable and Low-Cost Zn-Lignosulfonate Redox Flow Battery

Dataset: Aqueous organic redox flow batteries offer great promise for long-duration stationary energy storage but are often hindered by high costs associated with synthetic redox-active materials and expensive ion-exchange membranes. Polymer-based redox species allow the use of cheaper microporous membranes, yet synthetic redox polymers remain costly to produce. In this study, a cost-effective zinc/lignosulfonate hybrid redox flow battery (RFB) is presented, employing commercial sodium lignosulfonate (NaLS) as a biopolymer catholyte, Zn foil as a low-cost and abundant anode, and a cost-effective size-exclusion cellulose membrane as the separator. The sluggish electrochemical behavior of the NaLS is enhanced by using carbon-impregnated felt electrodes. Using 10 mM NaLS (20 kDa), the system achieves an average discharge voltage of 0.98 V and an initial capacity of 1.41 Ah L−1 (9.4 mAh g−1), outperforming previous lignin-based RFBs. Increasing NaLS concentration to 30 mM boosts capacity to 3.52 Ah L−1, although the cycling stability in 1 M ZnSO4 remains moderate. However, increasing the ZnSO4 concentration to 3 M further improves cyclability, with capacity retention rising to 72% over 28 days, compared to 66% over 17 days for 1 M ZnSO4. This work represents the first demonstration of commercial lignosulfonate as a catholyte in Zn-hybrid RFBs, showcasing its potential as a sustainable active material with a remarkably low electrolyte cost of 26 € kWh−1.