Rettie Alexander J E, Ding Jingxuan, Zhou Xiuquan, Johnson Michael J, Malliakas Christos D, Osti Naresh C, Chung Duck Young, Osborn Raymond, Delaire Olivier, Rosenkranz Stephan, Kanatzidis Mercouri G
Materials Science Division, Argonne National Laboratory, Lemont, IL, USA.
Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London, UK.
Nat Mater. 2021 Dec;20(12):1683-1688. doi: 10.1038/s41563-021-01053-9. Epub 2021 Jul 22.
Superionic conductors possess liquid-like ionic diffusivity in the solid state, finding wide applicability from electrolytes in energy storage to materials for thermoelectric energy conversion. Type I superionic conductors (for example, AgI, AgSe and so on) are defined by a first-order transition to the superionic state and have so far been found exclusively in three-dimensional crystal structures. Here, we reveal a two-dimensional type I superionic conductor, α-KAgSe, by scattering techniques and complementary simulations. Quasi-elastic neutron scattering and ab initio molecular dynamics simulations confirm that the superionic Ag ions are confined to subnanometre sheets, with the simulated local structure validated by experimental X-ray powder pair-distribution-function analysis. Finally, we demonstrate that the phase transition temperature can be controlled by chemical substitution of the alkali metal ions that compose the immobile charge-balancing layers. Our work thus extends the known classes of superionic conductors and will facilitate the design of new materials with tailored ionic conductivities and phase transitions.
超离子导体在固态下具有类似液体的离子扩散率，在从储能电解质到热电能量转换材料等领域有广泛应用。I型超离子导体（例如碘化银、硒化银等）由向超离子态的一级转变定义，迄今为止仅在三维晶体结构中被发现。在此，我们通过散射技术和补充模拟揭示了一种二维I型超离子导体α-KAgSe。准弹性中子散射和从头算分子动力学模拟证实，超离子银离子被限制在亚纳米片层中，通过实验X射线粉末对分布函数分析验证了模拟的局部结构。最后，我们证明了相变温度可以通过组成固定电荷平衡层的碱金属离子的化学取代来控制。因此，我们的工作扩展了已知的超离子导体类别，并将促进具有定制离子电导率和相变的新材料的设计。
