Electrochemical Decalcification-Exfoliation of Two-Dimensional Siligene, Si x Ge y : Material Characterization and Perspectives for Lithium-Ion Storage

A two-dimensional (2D) silicene-germanene alloy,siligene(Si x Ge y ),a single-phase material, has attracted increased attention due toits two-elemental low-buckled composition and unique physics and chemistry.This 2D material has the potential to address the challenges causedby low electrical conductivity and the environmental instability ofcorresponding monolayers. Yet, the siligene structure was studiedin theory, demonstrating the material's great electrochemicalpotential for energy storage applications. The synthesis of free-standingsiligene remains challenging and therefore hinders the research andits application. Herein we demonstrate nonaqueous electrochemicalexfoliation of a few-layer siligene from a Ca1.0Si1.0Ge1.0 Zintl phase precursor. The procedure wasconducted in an oxygen-free environment applying a -3.8 V potential.The obtained siligene exhibits a high quality, high uniformity, andexcellent crystallinity; the individual flake is within the micrometerlateral size. The 2D Si x Ge y was further explored as an anode material for lithium-ionstorage. Two types of anode have been fabricated and integrated intolithium-ion battery cells, namely, (1) siligene-graphene oxidesponges and (2) siligene-multiwalled carbon nanotubes. Theas-fabricated batteries both with/without siligene exhibit similarbehavior; however there is an increase in the electrochemical characteristicsof SiGe-integrated batteries by 10%. The corresponding batteries exhibita 1145.0 mAh center dot g(-1) specific capacity at 0.1 A center dot g(-1). The SiGe-integrated batteries demonstrate a verylow polarization, confirmed by their good stability after 50 workingcycles and a decrease in the solid electrolyte interphase level thatoccurs after the first discharge/charge cycle. We anticipate the growingpotential of emerging two-component 2D materials and their great promisefor energy storage and beyond.

Automated summary

This study successfully synthesized high-quality few-layer siligene through nonaqueous electrochemical exfoliation method, and evaluated its performance as an anode material for lithium-ion batteries. The results showed that the siligene exhibited excellent electrochemical characteristics and increased the capacity of the integrated batteries by 10%.