Solvent Volume Expansion Inhibition During Freeze Casting and its Application in Composite Solid Lithium Electrolytes

Abstract

Composite solid electrolytes hold the promise to enable all-solid-state lithium-ion batteries to be practicable. One critical issue is the construction of uniform porous ceramic framework. The work proposed an innovative freeze casting-based technology to construct porous ceramic framework of Li1+xAlxGe2−x(PO4)3 (LAGP), which was further composited with polymeric electrolytes to assemble full cells. The pore structure of the ceramic framework was effectively tuned by the ratio of mixed water-ethanol solvents, which could offset the volume expansion of water during freeze casting, benefit powder compact and sintering, and thus improved the quality of the composite solid electrolytes. The unique solvent composition design strategy provided ample opportunity for microstructural modification and the suppression of short-circuiting lithium dendrites, as demonstrated by the improvement of critical current density and phase field modeling. This work offers new perspectives on creating different pore structure free of residual stress or volume expansion once freeze casting technique is adopted.

Keywords: freeze casting, water-ethanol solvent, composite electrolytes, pore structure, volume expansion