Rare-Earth-Free Chloride Solid Electrolytes with High Ionic Conductivity for All-Solid-State Lithium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Commercialization of all-solid-state lithium batteries (ASSLBs) requires solid electrolytes (SEs) with high ionic conductivity (>1 mS cm⁻¹) and low cost (<$20 kg⁻¹).
• Existing SEs present a performance-cost dilemma: high conductivity often involves expensive precursors, while low-cost options lack sufficient conductivity.
• This limitation hinders the widespread adoption and cost-effectiveness of ASSLBs.

Purpose of the Study:

• To develop a novel, rare-earth-free chloride solid electrolyte (SE) that overcomes the performance-cost trade-off.
• To achieve simultaneously high ionic conductivity and low manufacturing cost for ASSLB applications.
• To investigate the ionic migration mechanisms and demonstrate the practical utility of the developed SE in ASSLB devices.

Main Methods:

• Synthesized a rare-earth-free chloride SE, Li₂.₀₃Zr₀.₉₈P₀.₀₂Cl₅.₉₅S₀.₀₅ (LZC-1PS), using a dual-site substitution strategy.
• Investigated ionic conductivity through electrochemical measurements, achieving room-temperature conductivity of 1.02 mS cm⁻¹.
• Fabricated lab-scale ASSLBs using LZC-1PS with Li₆PS₅Cl-coated Li-In anodes and NCM811 or LCO cathodes to evaluate performance.

Main Results:

• LZC-1PS exhibits ultralow cost ($15.21 kg⁻¹) and high room-temperature ionic conductivity (1.02 mS cm⁻¹).
• Dual-site substitution (S²⁻ for Cl⁻, P⁵⁺ for Zr⁴⁺) effectively reduces ion diffusion barriers and weakens Li⁺-anion interactions.
• ASSLBs utilizing LZC-1PS demonstrate excellent cycling stability, retaining 75.2% capacity after 1200 cycles (LCO) and 76.6% after 1000 cycles (NCM811) at 1C.

Conclusions:

• The developed LZC-1PS solid electrolyte successfully addresses the critical performance-cost challenge in ASSLB materials.
• This rare-earth-free material offers a promising pathway for the cost-effective commercialization of high-performance all-solid-state lithium batteries.
• The findings pave the way for next-generation energy storage solutions with enhanced safety and longevity.