Improved Performances of Zn//MnO2 Batteries with an Electrolyte Containing Co-Additives of Polyethylene Glycol and Lignin Derivatives

Multi-component electrolyte additives may significantly contribute to improving the performance of rechargeable aqueous zinc-ion batteries. Herein, we propose a mixed electrolyte system employing polyethylene glycol 200 (PEG200) and quaternized kraft lignin (QKL) as co-additives in Zn//MnO₂ batteries. Reduced corrosion and the suppression of the hydrogen evolution reaction on the zinc electrode were achieved when 0.5 wt.% of PEG200 and 0.2 wt.% of QKL were added to the reference aqueous electrolyte. This optimized electrolyte, 0.5% PEG200 + 0.2% QKL, was conducive to improving Zn reversibility in Zn//Zn symmetric batteries and resulted in higher cycling stability, with a coulombic efficiency of 98.01% under 1 mA cm^-2 and 1 mAh cm^-2 for Zn//Cu cells. Furthermore, Zn//MnO₂ full batteries with 0.5% PEG200 + 0.2% QKL presented good overall electrochemical performance and exhibited a decent discharge capacity of around 85 mAh g^-1 after 2000 cycles at 1.5 A g^-1. As confirmed by X-ray diffraction and scanning electron microscopy, a dominant (002) oriental dendrite-free Zn deposition was achieved on the zinc anode of the battery using 0.5% PEG200 + 0.2% QKL, and the byproducts were also reduced significantly. This study has contributed to the development of electrolyte co-additives for zinc-ion batteries.