Enhancing Zn anode stability with bioderived electrolyte additive for aqueous Zn-ion batteries

To overcome the limitations of short cycle life and poor reversibility of Zn-ion batteries, trace amounts (20 mM) of bioderived furfuryl alcohol (FAL) is introduced to the zinc sulfate (ZS) electrolyte. Density functional theory calculations, together with experimental characterization, indicate a preferential adsorption of FAL over H₂O molecules on Zn electrode surfaces, which suppresses parasitic reactions and generation of irreversible by-products e.g. Zn₄SO₄(OH)₆·xH₂O. FAL also increases the zinc deposition polarization, leading to heightened nucleation overpotential and slower deposition rates associated with planar growth of Zn film, in contrast to severe dendrite formation on FAL-free Zn surfaces. Consequently, the transference number of Zn²⁺ increases from 0.59 to 0.88 with the introduction of FAL. Zn||Zn symmetric cells with FAL additive exhibits an extreme cycle life of 4049 h at 1 mA cm⁻² and areal capacity of 1 mAh cm⁻². Similarly, ZnǀǀNaV₃O₈∙1.5H₂O (NVO) (N/P = 139) full cells with FAL exhibits a capacity retention 10 % higher, after 700 cycles at a rate of 1 A g⁻¹. In addition, Zn||V₂O₅ cell (N/P = 11) fails after 400 cycles but FAL additive enabled the cell to maintain a stable discharge capacity of 163 mAh g⁻¹ up to 1000 cycles.