Hydrogen-Bond Network Synergistic Regulation Strategy for Constructing Highly Stable VOPO₄·2H₂O Cathode in Aqueous Zinc-Ion Batteries AITranslate

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Chinese Library Classification Number:TM912[电气工程—电力电子与电力传动];O646.1[理学—物理化学]

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In aqueous zinc-ion batteries(AZIBs),the VOPO₄·2H₂O cathode material is prone to dissolu-tion due to erosion by free water in the electrolyte during charge-discharge cycles,resulting in severe vol-tage decay and capacity loss.By using its abundant sulfonyl oxygen atoms as hydrogen-bond acceptors,high-concentration LiTFSI can effectively reduce the content of free water and inhibit cathode dissolution.However,its high cost and high viscosity limit its practical application.To address this issue,this study proposes a synergistic replacement strategy for Zn(OTf)₂ electrolyte:Low-cost fructose(Fru)is used to partially replace high-concentration LiTFSI.Under the premise of maintaining a similar total number of hydrogen-bond acceptors,this strategy significantly reduces electrolyte viscosity and cost,optimizes Zn2+transport kinetics,and successfully constructs an optimized electrolyte system of 4.5 m Zn(OTf)₂+11 m Fru+8.5 m LiTFSI(m represents mol/kg H₂O).Systematic comparisons were conducted with 4 m Zn(OTf)₂ and 1 m Zn(OTf)₂+18 m LiTFSI electrolytes.Characterization results via XRD,SEM-EDS,and TEM demonstrate that VOPO₄·2H₂O powder exhibits good crystallinity and a distinct lamellar stacking structure.Immersion experiments show that the VOPO₄·2H₂O powder undergoes obvious dissolution within only 10 min in 4 m Zn(OTf)₂ electrolyte,while no significant dissolution occurs after immersing in the two LiTFSI-containing electrolytes for 10 d.Electrochemical test results indicate that the optimized electrolyte significantly improves the cycle stability and rate performance of the VOPO₄·2H₂O cathode,achieving a capacity retention rate of 95%after 150 cycles at 1 C,which is superior to that of the compara-tive systems.Kinetic analysis further reveals that the optimized electrolyte effectively reduces the charge transfer resistance and significantly improves the Zn2+diffusion coefficient.Raman spectroscopy confirms that in the optimized electrolyte,fructose molecules,with the flexible configuration of their five hydroxyl groups,synergize with abundant hydrogen-bonding sites on LiTFSI to form a dense hydrogen-bond net-work with water molecules,which significantly reduces the free water content,thereby inhibiting the disso-lution and irreversible phase transition of VOPO₄·2H₂O.This work solves the problems of high viscosity and cost of high-concentration LiTFSI electrolyte system through a low-cost and environmentally friendly electrolyte design strategy,provides an effective approach for the structural stabilization of VOPO₄·2H₂O cathode materials in AZIBs,and exhibits promising application potential.