Iodine-Doped Sodium Vanadate Cathode for Improved Zn Ion Diffusion Kinetics.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous zinc-ion batteries (AZIBs) face challenges due to strong electrostatic interactions between zinc ions and host materials, limiting cathode practicality.
• Vanadium-based compounds are promising cathodes, but their performance is hindered by electrostatic resistance and steric effects during zinc ion insertion.

Purpose of the Study:

• To mitigate electrostatic resistance and steric hindrance in vanadium-based cathodes for AZIBs.
• To improve the electrochemical performance and cycling stability of Na2V6O16·3H2O cathodes through anion doping.

Main Methods:

• Incorporation of iodine atoms into the Na2V6O16·3H2O lattice via an anion doping strategy.
• Investigation of the effects of iodine doping on zinc ion adsorption energy, diffusion kinetics, and host lattice structure.
• Electrochemical characterization to evaluate specific capacity, rate capability, and long-term cycling stability.

Main Results:

• Iodine doping significantly reduced Zn2+ adsorption energy and lowered the diffusion energy barrier, increasing the diffusion coefficient by an order of magnitude.
• The expanded host lattice due to iodine doping and oxygen vacancies provided enhanced zinc ion storage capacity.
• The iodine-doped Na2V6O16·3H2O cathode exhibited a high specific capacity of 528.8 mAh g-1 at 0.5 A g-1 and retained 262 mAh g-1 after 12,000 cycles at 10 A g-1.

Conclusions:

• Anion doping with iodine is an effective strategy to overcome limitations in vanadium-based cathodes for AZIBs.
• The developed cathode material demonstrates superior electrochemical performance, including high capacity and excellent cycling stability.
• This research offers valuable insights for designing advanced cathode materials for high-performance aqueous zinc-ion batteries.