Cold Sintering of LLTO Composite Electrolytes for Solid-State Lithium Batteries

Solid-state batteries have the potential for higher energy densities and enhanced safety when compared to conventional lithium-ion batteries. The perovskite-type Li_3xLa_2/3–xTiO₃ (LLTO) is an attractive ceramic electrolyte due to its high ionic conductivity, broad electrochemical stability window, and thermal and chemical stability. The conventional sintering process for ceramics, typically performed at high temperatures (~1000 °C), poses a critical bottleneck for integrating solid electrolytes with active electrode materials. In this study, Li_0.29La_0.57TiO₃/polypropylene carbonate (PPC) composite electrolytes containing lithium perchlorate (LiClO₄) were densified using cold sintering at 125 °C. The resulting LLTO-based composite electrolytes exhibit relative densities above 80 % and ionic conductivities exceeding 10⁻⁴ S cm⁻¹ at room temperature. The symmetric Li/LLTO-PPC-LiClO₄/Li cell with PVDF interlayers achieves a high critical current density of 1.8 mA cm⁻² at room temperature. Solid-state lithium batteries fabricated with LLTO composite solid electrolytes deliver a high discharge capacity of 151 mAh g⁻¹ at 0.1 C and 135 mAh g⁻¹ at 0.2 C. Our approach, which integrates ceramic and polymer materials, produces composite electrolytes with superior properties, highlighting the potential of cold sintering for advancing solid-state batteries.