Molecular Surface Engineering of Sulfide Electrolytes with Enhanced Humidity Tolerance for Robust Lithium Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Solid-state electrolytes (SSEs) are crucial for next-generation batteries, offering enhanced safety and compatibility with lithium metal anodes.
• Sulfide-based SSEs, while promising, face challenges like limited electrochemical stability and high moisture sensitivity.
• Stabilizing interfaces in SSEs is key to improving battery performance and longevity.

Purpose of the Study:

• To develop a molecular surface engineering strategy for Li argyrodite SSEs (Li₆PS₅Cl_0.5Br_0.5) using octadecyl phosphonic acid (OPA) and its lithiated form (Li-OPA).
• To enhance the electrochemical stability and moisture resistance of the SSE.
• To improve the interfacial compatibility between the SSE and both anode and cathode materials in all-solid-state batteries.

Main Methods:

• A single-step coating strategy using OPA and Li-OPA was employed to modify the surface of Li₆PS₅Cl_0.5Br_0.5 (LPSClBr).
• Electrochemical performance was evaluated, including ionic conductivity, critical current density, and Li plating/stripping stability.
• All-solid-state cells utilizing NCM811 cathodes and anode-free configurations were assembled and cycled to assess performance.

Main Results:

• The Li-OPA-coated electrolyte maintained high ionic conductivity (>2.5 mS cm^-1) and excellent moisture resistance (>92% conductivity retention after 24h).
• Stable Li plating/stripping was achieved for over 400h at 1.0 mAh cm^-2 with a critical current density of 2.4 mA cm^-1.
• All-solid-state cells demonstrated high reversible capacity (160 mAh g^-1 at 0.3 C), excellent Coulombic efficiency (>99.7%), and good cycling stability (85% retention after 100 cycles).

Conclusions:

• Molecular surface engineering with Li-OPA effectively stabilizes sulfide-based SSEs against moisture and improves interfacial contact.
• The Li-OPA modification enhances critical current density and enables stable lithium metal cycling.
• This scalable strategy offers a promising pathway for developing high-performance, safe sulfide-based all-solid-state batteries.