Reversible Deposition/Dissolution of Double Hydroxides to Modulate Electrolyte pH Enabling High-Performance Aqueous...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Vanadium oxide (VO2) is a promising cathode material for zinc-ion batteries but faces challenges like low conductivity and poor cycling stability.
• Byproduct accumulation and dissolution during cycling hinder the practical application of VO2-based cathodes.

Purpose of the Study:

• To develop a stable and high-performance VO2-based cathode for aqueous zinc-ion batteries.
• To investigate the role of a specific byproduct, Zn12(CF3SO3)9(OH)15·nH2O (ZCOH), in improving battery performance.

Main Methods:

• Hydrothermal synthesis of VO2@MXene Ti3C2 (MV) composite.
• Electrochemical testing of MV//Zn cells in 3 M Zn(CF3SO3)2 electrolyte.
• In situ X-ray diffraction and in situ pH measurements.
• Theoretical calculations for ZCOH decomposition energy.

Main Results:

• The synthesized MV composite demonstrated reversible ZCOH formation and dissolution, acting as a pH buffer.
• In situ studies confirmed ZCOH's buffering effect, enhancing cycling stability.
• Theoretical calculations showed lower ZCOH decomposition energy on MV compared to pure VO2.
• Coin cells achieved 80.7% capacity retention after 20,000 cycles and 65.1% at 15 A g-1.
• A soft-packaged battery maintained 72.1% capacity after 2000 cycles.

Conclusions:

• The ZCOH byproduct plays an active, beneficial role in the electrochemical cycling of VO2 cathodes.
• The MV composite offers a viable strategy for developing high-performance aqueous zinc-ion batteries.
• Understanding and controlling byproduct behavior is crucial for advancing vanadium oxide cathode materials.