Suppressing Unfavorable Interfacial Reactions Using Polyanionic Oxides as Efficient Buffer Layers: Low-Cost Li₃PO₄...

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• All-solid-state batteries (ASSBs) with sulfide electrolytes suffer from poor electrochemical performance due to interfacial side reactions.
• Existing cathode coatings like LiNbO₃ and Li₂ZrO₃ are effective but costly, hindering mass production.
• The cathode/sulfide-electrolyte interface is a critical area for performance degradation in ASSBs.

Purpose of the Study:

• To investigate Li₃PO₄ as a novel, low-cost coating material for ASSB cathodes.
• To evaluate the impact of Li₃PO₄ coatings on interfacial stability and electrochemical performance.
• To demonstrate the potential of Li₃PO₄ as a commercially viable coating for ASSBs.

Main Methods:

• Li₃PO₄ coatings were applied to ASSB cathodes using low-cost precursors (polyphosphoric acid and lithium acetate).
• Electrochemical performance was assessed, including discharge capacities, rate capabilities, and cyclic stability.
• Interfacial reactions and interdiffusion were analyzed to understand the coating's mechanism.

Main Results:

• Li₃PO₄ coatings significantly improved discharge capacities (e.g., from ~181 mAh·g⁻¹ to ~194-195 mAh·g⁻¹).
• Capacity retention over 50 cycles improved substantially (from ~72% for pristine to ~84-85% for coated cathodes).
• The Li₃PO₄ coating effectively suppressed side reactions and interdiffusion at the cathode/sulfide-electrolyte interface.

Conclusions:

• Li₃PO₄ is a promising, cost-effective coating material for enhancing ASSB performance.
• The phosphate coating effectively stabilizes the cathode/electrolyte interface, preventing degradation.
• This research highlights the potential of low-cost polyanionic oxides for commercial ASSB applications.