Atomic-scale unveiling of multiphase evolution during hydrated Zn-ion insertion in vanadium oxide

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Electrochemical insertion of cations into crystalline lattices can induce phase transformations.
• Understanding these phase evolutions at the atomic level is critical for optimizing energy storage capacity in rechargeable cells.
• Identifying intermediate phases during transformation is often challenging with conventional methods.

Purpose of the Study:

• To directly visualize the atomic-level phase evolution during zinc-ion insertion into a V2O5 cathode using advanced microscopy.
• To identify previously unobserved intermediate phases and their structural relationships during the discharge process.
• To correlate smooth multiphase evolution with high capacity in oxide cathodes for aqueous rechargeable batteries.

Main Methods:

• Atomic-column-resolved scanning transmission electron microscopy (STEM) was employed to achieve atomic-scale imaging.
• Simultaneous intercalation of water (H2O) and zinc (Zn) cations during battery discharge was directly observed.
• High-resolution imaging allowed for the identification of multiple intermediate phases not detectable by powder diffraction.

Main Results:

• Direct visualization of simultaneous H2O and Zn intercalation into the V2O5 cathode during discharge.
• Identification of multiple intermediate phases with clear topotactic correlations, previously undetected by macroscopic methods.
• Atomic-scale imaging revealed the structural details of phase evolution during zinc insertion.

Conclusions:

• Smooth multiphase evolution with a low transition barrier is a key factor for achieving high capacity in oxide cathodes for aqueous rechargeable cells.
• The crystal structure of cathode materials can significantly change after discharge compared to the initial state.
• Direct atomic-level observation provides crucial insights into the mechanisms governing cation insertion and phase transformation in battery materials.