KB₃H₈·NH₃B₃H₇ Complex as a Potential Solid-State Electrolyte with Excellent Stability against K Metal

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• All-solid-state potassium batteries offer safe and cost-effective large-scale energy storage.
• Developing solid-state electrolytes with high ionic conductivity and interfacial stability remains a key challenge.

Purpose of the Study:

• To synthesize novel solid-state K-ion conductors based on KB3H8·nNH3B3H7 complexes.
• To evaluate their potential as electrolytes for all-solid-state potassium batteries.

Main Methods:

• Synthesis of KB3H8·nNH3B3H7 (n = 0.5, 1) complexes.
• Analysis of phase transitions and thermal stability.
• Measurement of ionic conductivity, transference number, and electrochemical stability window.

Main Results:

• The optimal KB3H8·NH3B3H7 exhibits a reversible phase transition and a record K-ion conductivity of 1.3 × 10^-4 S cm^-1 at 55 °C.
• Achieved high K-ion transference number (~0.93) and electrochemical stability window (1.2–3.5 V vs K+/K).
• Demonstrated excellent K dendrite suppression and anode interfacial stability.

Conclusions:

• KB3H8·NH3B3H7 is a leading solid-state K-ion conductor for advanced potassium batteries.
• The material's properties address critical challenges in solid-state electrolyte development.
• Promising for the realization of safe and high-performance all-solid-state potassium batteries.