Formation of 2:1 Li-Fe-phyllosilicate with montmorillonite-like structure in hydrothermal conditions

Abstract

Here, we report on hydrothermal synthesis and structural characterization of Li-Fe-montmorillonite (MMT). To date, this 2:1 type phyllosilicate attracts attention due to such properties as high ion mobility, hydrophilicity, electrical and thermal resistance. Due to that, various MMTs may serve as perspective components of Li-ion batteries (electrolyte and separator fillers, as well as protective buffer layer on top of Li metal anode). Scarce data on synthetic Li-Fe³⁺-MMTs motivated us to investigate formation process and structure features of such phyllosilicate by X-ray diffraction, UV-visible and Mössbauer spectroscopy, and other methods. We established critical Fe³⁺ content and temperature range needed for almost single-phase MMTs formation. Around 20% of total Fe may occupy tetrahedral site of MMT layer. Thermal behavior of Li-Fe-MMT strongly depends on hydrothermal synthesis conditions because of different Li⁺ amount present in the interlayer space and in the layer vacancies.