Synthesis of Lithium Silicides, Germanides and Stannides with Ion Exchange Materials

由于两个原因，硅、锗和锡元素的二元锂化合物是有趣的可再生能源材料，即它们可以作为具有有趣的光电性质的半导体硅和锗同素异形体的负极材料和前体材料。在初步的实验和理论研究中，申请人已经证明了九原子团簇E9可以在溶液中氧化偶联，并且可以从含锂的前体中获得元素的新的亚稳同素异形体。理论研究也表明，含有九个原子团簇的元素的同素异形体是稳定的。具有直接带隙的材料显著提高了太阳能电池的效率。在该项目中，将利用离子交换技术，从更重、更容易获得的同系物开始，系统地开发具有九原子簇E9的含锂锌相E9。在初步研究过程中，以K4Sn9为原料，通过液氨离子交换合成Li4Sn9的新路线的成功，证明了这一新的合成路线的原理。接下来，产物中的锂应该用我们实验室开发的用于其他含锂化合物(例如Li7Ge12)的氧化脱除方法进行氧化去除。在最好的情况下，这应该会导致对仍然包含九个原子团簇并具有直接带隙的元素进行新的修改。

For two reasons binary lithium compounds of the elements Si, Ge and Sn are interesting materials for renewable energy sources, i. e. they can serve as anode materials and as precursor materials for semiconducting Si and Ge allotropes with interesting optoelectronical properties. In preliminary experimental and theoretical studies the applicant has shown that nine-atom clusters E9 can be oxidatively coupled in solution, and that new metastable allotropes of the elements can be obtained from lithium-containing precursors. The stability of allotropes of the elements which contain nine-atom clusters has also been indicated by theoretical investigations. Materials with direct band gaps significantly increase the efficiency of solar cells. Within this project the class of lithium-containing Zintl phases with nine-atom clusters E9, which are not directly accessible so far, are to be developed systematically, starting from the heavier, better-accessible homologues by using ion exchange techniques. The successful synthesis of Li4Sn9 from K4Sn9 via this novel synthetic route for this kind of compounds by ion exchange in liquid ammonia in the course of preliminary studies serves as a proof of principle. In the following, the lithium in the resulting products should be removed oxidatively by using established methods developed in our laboratory for the delithiation of other lithium-containing compounds (e. g. Li7Ge12). This should in best-case lead to new modifications of the elements which still contain the nine atom clusters and possess direct band gaps.