Enhanced Ionic Conductivity in Bidisperse Solid Electrolytes

The search for safe, reliable, and compact high-capacity energy storage devices has led to an increased interest in all-solid-state battery research. Solid electrolytes provide enhanced safety and durability due to their reduced volatility and increased mechanical strength compared with organic liquid electrolytes. Using a particle dynamics electromechanics computational model, the ionic conductivity of a solid electrolyte comprised of bidisperse grain size consisting of a mixture of coarse and fine particles is examined. Simulations show increased densification and ion conductivity in the region of 10 to 30 vol % fine particle content. The conditions and mechanisms of the conductivity enhancement are analyzed, showing that high grain boundary conductivity equal to or above the bulk conductivity of the electrolyte particles and a grain size ratio between large and small particles above 3 are essential requirements for the global conductivity enhancement. Experimental tests on a Li₆PS₅Cl electrolyte containing 1 μm and 5 μm particles confirm these findings.