Dual Vacancy-Driven "Lattice Softening" NiFeAl_x LDHs for High-Rate and Durable Chloride Ion Storage

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Defect engineering is crucial for electrochemical performance but underexplored in anion-based systems like chloride-ion batteries (CIBs).
• Layered double hydroxides (LDHs) are promising electrode materials, but often suffer from poor structural stability during anion intercalation/de-intercalation.

Purpose of the Study:

• To develop a defect-engineering strategy for enhancing the electrochemical performance of LDHs in CIBs.
• To investigate the role of coexisting cationic and oxygen vacancies in improving structural flexibility and ion transport.

Main Methods:

• Synthesized dual-vacancy NiFeAl LDHs using a room-temperature alkaline etching process.
• Characterized the material's structure, defects, and electrochemical properties.
• Performed multiscale mechanistic analyses to understand the role of vacancies.

Main Results:

• Optimized NiFeAl LDH (NiFeAl0.04-24h-Cl LDH) demonstrated "lattice softening" for elastic deformation and structural reconstruction.
• Achieved high reversible capacity (101.4 mAh g-1 at 1000 mA g-1) and excellent cycling stability (1000 cycles) with 99.91% Coulombic efficiency.
• Vacancies facilitated enhanced chloride ion accommodation, accelerated ion diffusion, and improved interfacial kinetics.

Conclusions:

• Dual-vacancy engineering in NiFeAl LDHs provides lattice adaptability, resolving the capacity-stability trade-off in anion-hosting electrodes.
• This strategy offers a promising pathway for designing efficient electrodes for advanced chloride-ion battery systems.