Structural Characterization of Oxyhalide Materials for Solid-State Batteries

Development of materials with novel composition to obtain rechargeable solid-state batteries with improved capacity and energy density is one of the hot topics in material science. Inorganic and thermally stable oxyhalide materials are potential substitutes for the toxic and flammable organic liquid electrolytes used in the Li-ion batteries. Herein, Li-, Na-, and K-ion-based oxyhalide materials doped with Ca, Ba, and Mg are synthesized. The samples are characterized by neutron and X-ray diffractometry, Raman spectroscopy, thermal analysis, and transmission electron microscopy (TEM). Significant differences can be observed between the Li/Na/K-series, but within the series the diffraction character of the compositions is similar; semi-amorphous/crystalline phases are identified. Characteristic first- and second-neighbor distributions reveal a very compact network structure. X-ray diffractometry and Raman studies prove that the investigated Li-, Na-, and K-based samples absorb water, even if they are kept under dry conditions. The Li3OCl antiperovskite phase is identified by X-ray diffraction (XRD) in all the Ca-, Ba-, and Mg-doped samples. TEM studies show that the morphology of the samples consists of nanograins of different size below 100 nm. According to elemental maps, the doping Ba forms oxide nanoparticles, while Mg is incorporated into the Na- and K-based network structure.