Brinek Marina, Hiebl Caroline, Wilkening H Martin R
Institute for Chemistry and Technology of Materials, Christian Doppler Laboratory for Lithium Batteries, Graz University of Technology (NAWI Graz), Stremayrgasse 9, 8010 Graz, Austria.
Chem Mater. 2020 Jun 9;32(11):4754-4766. doi: 10.1021/acs.chemmater.0c01367. Epub 2020 May 19.
Argyrodite-type LiPSX (X = Cl, Br) compounds are considered to act as powerful ionic conductors in next-generation all-solid-state lithium batteries. In contrast to LiPSBr and LiPSCl compounds showing ionic conductivities on the order of several mS cm, the iodine compound LiPSI turned out to be a poor ionic conductor. This difference has been explained by anion site disorder in LiPSBr and LiPSCl leading to facile through-going, that is, long-range ion transport. In the structurally ordered compound, LiPSI, long-range ion transport is, however, interrupted because the important intercage Li jump-diffusion pathway, enabling the ions to diffuse over long distances, is characterized by higher activation energy than that in the sibling compounds. Here, we introduced structural disorder in the iodide by soft mechanical treatment and took advantage of a high-energy planetary mill to prepare nanocrystalline LiPSI. A milling time of only 120 min turned out to be sufficient to boost ionic conductivity by 2 orders of magnitude, reaching σ = 0.5 × 10 S cm. We followed this noticeable increase in ionic conductivity by broad-band conductivity spectroscopy and Li nuclear magnetic relaxation. X-ray powder diffraction and high-resolution Li, P MAS NMR helped characterize structural changes and the extent of disorder introduced. Changes in attempt frequency, activation entropy, and charge carrier concentration seem to be responsible for this increase.
硫银锗矿型LiPSX（X = Cl，Br）化合物被认为是下一代全固态锂电池中强大的离子导体。与离子电导率在几mS cm量级的LiPSBr和LiPSCl化合物不同，碘化合物LiPSI结果证明是一种较差的离子导体。这种差异已通过LiPSBr和LiPSCl中的阴离子位点无序导致的便捷贯穿（即长程离子传输）来解释。然而，在结构有序的化合物LiPSI中，长程离子传输被中断，因为重要的笼间Li跳跃扩散途径（使离子能够长距离扩散）的特征是具有比其同族化合物更高的活化能。在这里，我们通过软机械处理在碘化物中引入结构无序，并利用高能行星式球磨机制备了纳米晶LiPSI。结果表明，仅120分钟的球磨时间就足以使离子电导率提高2个数量级，达到σ = 0.5×10 S cm。我们通过宽带电导率光谱和锂核磁共振弛豫跟踪了离子电导率的这种显著增加。X射线粉末衍射和高分辨率锂、磷固体核磁共振有助于表征结构变化和引入的无序程度。尝试频率、活化熵和载流子浓度的变化似乎是这种增加的原因。
