Safe and extended operating voltage zinc-ion battery engineered by a gel-polymer/ionic-liquid electrolyte and water molecules pre-intercalated V2O5 cathode

Abstract

Zinc-ion batteries (ZIBs) represent a promising technology since highly safe water or gel polymer electrolytes (GPE) are reliable and environmentally benign and have significant grid-level storage applications. However, Zn2+ strong charge interactions with the host cathode lattice result in poor reversibility, unwanted side reaction in the aqueous electrolyte, and sluggish Zn2+ diffusion in GPE, limitting its real-time application. Herein, we report the development of a large-scale water-molecule pre-intercalated sheet-like V2O5 (s-V2O5·0.56H2O) cathode and GPE to address the aforementioned issues. The transparent GPE prepared by mixing poly(vinylidene fluoride-co-hexafluoropropylene), 1-ethyl-3-methylimidazolium tetrafluoroborate, and zinc trifluoromethanesulfonate. The s-V2O5·0.56H2O exhibited a higher diffusion coefficient (2.46 × 10−10 cm−2 s−1) than the commercial V2O5 (2.18 × 10−11 cm−2 s−1) electrode. The Zn2+ intercalation/deintercalation and protonation/deprotonation mechanisms were investigated by ex-situ Raman and X-ray photoelectron spectroscopies in discharged (0.2 V) and charged (1.5 V) states. Overall, the s-V2O5·0.56H2O cell in aqueous and GPE medium demonstrated a high capacity of 407 and 197 mAh/g (0.2 A/g), respectively. The aqueous and GPE mediated cell revealed high Coulombic efficiency (98 % and ∼ 100 % after 1000 cycles) and long-term cycling stability (for aqueous: 69 % and GPE: 74 % at 1000 cycles). The ex-situ surface study of the Zn anode revealed the flat zinc plating upon GPE usage rather than the aqueous electrolyte flake structure. This water-molecule pre-intercalated sheet-like V2O5 cathode with GPE cell as potential Zn2+ ion battery power supplied to the liquid crystal display monitor.