Amorphous conductors with high ionic conductivity are a promising candidate as electrolytes in all-solid state batteries. In this work, we prepared amorphous Ag 3 PS 4 conductor via a chemo-mechanical milling process, and then characterized its structure and electrochemical properties . The results show that Ag + conductivity of the amorphous Ag 3 PS 4 was remarkably enhanced by three orders of magnitude compared to its crystalline counterpart. Furthermore, the amorphous sample exhibits lower activation energy ( E a ) for ionic conductivity as a function of temperature. Structural characterizations indicate that the tetrahedral [PS 4 ] units were retained in amorphous Ag 3 PS 4 , but the Ag + ions became more liberated than those in the crystalline state, leading to the enhanced migration of Ag + ions, thereby, the ionic conductivity in amorphous Ag 3 PS 4 is drastically increased. This work provides insight into the crucial role of the disorder in raising the ionic conductivity of amorphized chalcogenide materials containing mobile ions.
Wanchun Qiao,Ang Qiao,Yunhang Tao,Shaoxuan Gu,Yuanzheng Yue,Haizheng Tao
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.
In this work we succeeded in synthesizing a chalcogenide glass, that is, the Ag 3 PS 4 glass, by milling the mixture of the crystalline Ag 2 S and P 2 S 5 powder. In terms of potential energy, the glass was excited by the milling process. The evidence for the energy excitation was the occurrence of the sub- T g relaxation recorded by a differential scanning calorimeter (DSC). The relaxation behavior in the milling-derived Ag 3 PS 4 glass was found to significantly differ from that of a hyperquenched oxide glass. We observed two decoupled peaks of the energy release during a DSC scan, which are in contrast to the single asymmetric peak of the hyperquenched glass. The low-temperature peak could be attributed to the β-relaxation of the Ag–S ionic bonds, whereas the high-temperature peak could arise from the α-relaxation of the distorted rigid [PS 4 ] units involving covalent bonds. The decoupling between the two peaks implies the fragile nature of the Ag 3 PS 4 glass. Upon the dynamic heating and the sub- T g annealing we found that the relaxation of the Ag 3 PS 4 glass is of high nonexponentiallity, and hence, of high structural heterogeneity.
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