A High Potential Polyanion Cathode Material for Rechargeable Mg-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Magnesium-ion batteries (MIBs) are promising for energy storage but are limited by cathode material performance.
• Developing MIBs requires materials with facile and reversible Mg2+ intercalation at high potentials.

Purpose of the Study:

• To introduce a novel polyanion cathode material, KVPCH, for MIBs.
• To investigate the structural and electrochemical properties of KVPCH for enhanced Mg2+ storage.

Main Methods:

• Synthesis and characterization of K2(VO)2(HPO4)2(C2O4)·4.5H2O (KVPCH).
• Electrochemical testing including cyclic voltammetry and galvanostatic cycling.
• Experimental analysis and theoretical calculations to understand Mg2+ diffusion and desolvation.
• Fabrication and testing of a rocking-chair MIB full cell.

Main Results:

• KVPCH exhibits a high redox potential due to the inductive effect of polyanions.
• Structural water in KVPCH facilitates Mg2+ desolvation and diffusion.
• The KVPCH electrode delivers 121 mAh g-1 capacity at 1C with a high average discharge potential (3.2 V vs Mg/Mg2+).
• Excellent cycling stability with 87% capacity retention after 1500 cycles at 5C.
• A full cell demonstrated 46 mAh g-1 capacity.

Conclusions:

• KVPCH is a promising cathode material for high-performance MIBs.
• The design principles, including polyanion structure and structural water, offer effective strategies for developing future MIB cathode materials.