Enhanced Structure Ductility and Sodium Storage Kinetics of High-Capacity Sulfide Anodes via Medium-Entropy...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Metal sulfide anodes show promise for sodium-ion batteries due to high theoretical capacities.
• However, they suffer from chemo-mechanical degradation, poor conductivity, and slow ion transport, limiting their practical application.

Purpose of the Study:

• To develop a mechanics-led design strategy for improving the durability and performance of metal sulfide anodes.
• To engineer a ductile ternary thiospinel (ME-NCUS) using medium-entropy ductility engineering for enhanced sodium storage.

Main Methods:

• Utilized density functional theory (DFT) to calculate elastic constants (Pugh ratio, Poisson's ratio, Young's modulus) and assess mechanical properties.
• Investigated the material's response to sodiation/desodiation and its impact on electrode integrity and interfaces.
• Evaluated electrochemical performance, including capacity retention, cycling stability, and ion kinetics.

Main Results:

• ME-NCUS exhibits an intrinsically ductile and compliant lattice, effectively accommodating strain and dissipating stress.
• The engineered mechanical properties mitigate volume expansion, suppress crack propagation, and stabilize electrode/electrolyte interfaces.
• Achieved excellent durability, retaining 92% capacity after 900 cycles at 5 A g⁻¹, with accelerated sodium-ion kinetics.

Conclusions:

• Ductility is a critical design parameter for high-capacity anodes with large volume changes.
• Medium-entropy engineering provides a scalable approach to create mechanically resilient and kinetically fast conversion/alloying anodes for sodium storage.