Facile Synthesis of Two-Dimensional Natural Vermiculite Films for High-Performance Solid-State Electrolytes

Abstract

Ceramic electrolytes hold application prospects in all-solid-state lithium batteries (ASSLB). However, the ionic conductivity of ceramic electrolytes is limited by their large thickness and intrinsic resistance. To cope with this challenge, a two-dimensional (2D) vermiculite film has been successfully prepared by self-assembling expanded vermiculite nanosheets. The raw vermiculite mineral is first exfoliated to thin sheets of several atomic layers with about 1.2 nm interlayer channels by a thermal expansion and ionic exchanging treatment. Then, through vacuum filtration, the ion-exchanged expanded vermiculite (IEVMT) sheets can be assembled into thin films with a controllable thickness. Benefiting from the thin thickness and naturally lamellar framework, the as-prepared IEVMT thin film exhibits excellent ionic conductivity of 0.310 S·cm−1 at 600 °C with low excitation energy. In addition, the IEVMT thin film demonstrates good mechanical and thermal stability with a low coefficient of friction of 0.51 and a low thermal conductivity of 3.9 × 10−3 W·m−1·K−1. This reveals that reducing the thickness and utilizing the framework is effective in increasing the ionic conductivity and provides a promising stable and low-cost candidate for high-performance solid electrolytes.

A comprehensive review of atomically thin silicates and their applications

“…Recently, the solid-state electrolyte performance of a film made by assembling 2D vermiculite sheets, where the 2D vermiculite is prepared by thermal expansion and ion-exchange treatment, has been reported. Through a 2D vermiculite film, an ionic conductivity of 0.310 S•cm −1 with low excitation energy was observed at 600 • C [89]. Vermiculite nanosheets are also utilized to extract functional core layers, such as MgO and Fe 2 O 3 sandwiched between two tetrahedral layers of SiO 2 and Al 2 O 3 in vermiculite structures (figure 6(d)) [87].…”