Structural Origins of the Enhancement in Ionic Conductivity of a Chalcogenide Compound by Adding AgI

Graphical Mill and heat : A chemo-mechanical milling process is used to prepare a highly conductive amorphous 0.5AgI ⋅ 0.5 Ag 3 PS 4 conductor. The mechanisms of the enhancement in ionic conductivity for the present 0.5AgI ⋅ 0.5 Ag 3 PS 4 amorphous powder together with the heat-treated one are discussed. Through a chemo-mechanical milling process, we prepared a highly conductive (1.1×10 −3 S ⋅ cm −1 ) amorphous 0.5AgI ⋅ 0.5 Ag 3 PS 4 conductor, which is much higher than that of pure amorphous Ag 3 PS 4 (8.5×10 −4 S ⋅ cm −1 ). Detailed structural characterizations indicate that compared to the ionic conductivity of the amorphous Ag 3 PS 4 conductor, the enhancement can be ascribed to the formation of mixed polymeric anions {[PS 4 ] m I n } around Ag + ions. Through heat-treatment at 370 °C for 20 minutes, the room temperature ionic conductivity of the 0.5AgI ⋅ 0.5 Ag 3 PS 4 conductor is further enhanced by about 4 times. This enhancement can be ascribed to the following two aspects: 1) the existence of residual amorphous phase with higher ionic conductivity; 2) the connection of the fast ionic conductive interfaces between the deposited Ag 7 PS 6 nano-crystals and the residual amorphous phase. This work reveals the key roles of both disorder and interface in improving the ionic conductivity of solid-state electrolytes.