Solute-solvent dual engineering toward versatile electrolyte for high-voltage aqueous zinc-based energy storage devices

Manufacturing cost-effective electrolytes featuring high (electro)chemical stability, high Zn anode reversibility, good ionic conductivity, and environmental benignity is highly desired for rechargeable aqueous zinc-based energy storage devices but remains a great challenge. Herein, a solute-solvent dual engineering strategy using lithium bis(trifluoromethane)sulfonimide (LiTFSI) and inexpensive poly(ethylene glycol) (PEG, M_n = 200) as a coadditive with an optimized ratio accomplished an all-round performance enhancement of electrolytes. Due to the synergistic inhibition of water activity and Zn²⁺ solvation structure reorganization by LiTFSI-PEG, as well as a stable F-rich interfacial layer and PEG adsorption on the Zn anode surface, dendrite-free Zn plating/stripping at nearly 100% Coulombic efficiency and stable cycling performance over 2000 h at 0.5 mA cm⁻² was achieved. Importantly, the integrated Zn-ion hybrid supercapacitors are endowed with a wide voltage window of 0–2.2 V, superb cycling stability up to 10,000 cycles, and excellent temperature adaptability from -40 °C to 50 °C. The highest cutoff voltage reached 2.1 V in Zn//LiMn₂O₄ and Zn//VOPO₄ full cells with a stable lifespan over 500 cycles. This work provides a promising strategy for the development of aqueous electrolytes with excellent comprehensive properties for zinc-based energy storage.