Solubility-Limited Small Molecule for Stable High-Capacity Potassium Storage.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Small molecule electrode materials offer high redox activity for potassium-ion (K-ion) storage.
• Challenges include high electrolyte solubility and low conductivity, hindering performance.
• Need for stable, high-performance anode materials for K-ion batteries.

Purpose of the Study:

• Design and synthesize Ni-bis(dithiolene) (NiS4)-based small molecules for K-ion battery anodes.
• Investigate the impact of redox-active substitutional groups on electrochemical performance.
• Address solubility and conductivity limitations in small molecule electrode materials.

Main Methods:

• Synthesis of a series of NiS4-based small molecules with varying substituents.
• Electrochemical characterization including capacity, rate capability, and cycling stability tests.
• Comprehensive material characterization and theoretical simulations (e.g., DFT) to elucidate storage mechanisms.

Main Results:

• Bis[1,2-di(pyridine-4-yl) ethylene-1,2-dithiolate] nickel (Ni[C2S2Py2]2) achieved a high reversible specific capacity of 399 mAh g⁻¹ at 0.03 A g⁻¹.
• Demonstrated impressive rate capability and exceptional cycling stability with over 99% capacity retention after 1600 cycles.
• Synergistic effects between NiS4 and pyridine groups enhance K⁺ storage, conductivity, and reduce solubility.

Conclusions:

• Ni[C2S2Py2]2 exhibits extraordinary performance as a K-ion battery anode material.
• Multistep K⁺ storage mechanism confirmed, enabling fast charge transfer and excellent rate performance.
• Presents a promising strategy for developing soluble-limited, conductive small molecule electrodes for non-aqueous rechargeable batteries.