Ultrathin, Mechanically Robust Quasi-Solid Composite Electrolyte for Solid-State Lithium Metal Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Solid-state lithium metal batteries (SLBs) offer enhanced safety and energy density compared to conventional lithium-ion batteries.
• Developing mechanically robust and ionically conductive electrolytes remains a key challenge for practical SLB applications.
• Quasi-solid electrolytes bridge the gap between liquid and solid electrolytes, offering improved safety and processability.

Purpose of the Study:

• To prepare and characterize an ultrathin, mechanically robust quasi-solid composite electrolyte (SEO-QSCE) for high-voltage SLBs.
• To evaluate the electrochemical performance, mechanical properties, and lithium dendrite suppression capabilities of the developed electrolyte.
• To demonstrate the potential of the SEO-QSCE in practical SLB devices.

Main Methods:

• Synthesis of a quasi-solid composite electrolyte using polystyrene-b-poly(ethylene oxide) diblock copolymer, Li_6.75La₃Zr_1.75Ta_0.25O₁₂ nanofiller, and fluoroethylene carbonate plasticizer.
• Characterization of the electrolyte's microstructure, ionic conductivity, tensile strength, and elastic modulus.
• Assembly and testing of SLBs with LiFePO₄ and LiNi_0.5Co_0.3Mn_0.2O₂ cathodes to evaluate cycling performance and stability.

Main Results:

• The SEO-QSCE exhibits bicontinuous phases with high ionic conductivity (1.3 × 10^-3 S cm^-1 at 30 °C) and remarkable mechanical strength (5.1 MPa tensile strength, 2.7 GPa elastic modulus).
• The electrolyte effectively suppresses lithium dendrite growth, enabling stable cycling over 600 cycles for Li|SEO-QSCE|LiFePO₄ cells.
• High-voltage SLBs utilizing LiNi_0.5Co_0.3Mn_0.2O₂ cathodes demonstrate good cycling stability and flexibility in pouch cells.

Conclusions:

• The developed ultrathin, mechanically robust SEO-QSCE is a promising electrolyte for high-voltage solid-state lithium metal batteries.
• The unique bicontinuous phase structure and mechanical integrity contribute to superior electrochemical performance and safety.
• This work presents an innovative approach for designing advanced quasi-solid electrolytes for next-generation energy storage devices.