A general Lewis acidic etching route for preparing MXenes with enhanced electrochemical performance in non-aqueous electrolyte

TL;DR

This paper introduces a novel Lewis acidic melt etching method for synthesizing MXenes from unconventional MAX phases, resulting in materials with enhanced electrochemical performance for energy storage.

Contribution

It presents a new redox-controlled A-site-etching technique in Lewis acidic melts to produce MXenes from non-Al MAX phases, expanding synthesis options.

Findings

MXenes synthesized from Si, Zn, Ga MAX phases show high electrochemical capacity.

Ti3C2 MXene exhibits up to 738 C g-1 (205 mAh g-1) capacity.

The method enables high-rate performance in lithium-ion batteries.

Abstract

Two-dimensional carbides and nitrides of transition metals, known as MXenes, are a fast-growing family of 2D materials that draw attention as energy storage materials. So far, MXenes are mainly prepared from Al-containing MAX phases (where A = Al) by Al dissolution in F-containing solution, but most other MAX phases have not been explored. Here, a redox-controlled A-site-etching of MAX phases in Lewis acidic melts is proposed and validated by the synthesis of various MXenes from unconventional MAX phase precursors with A elements Si, Zn, and Ga. A negative electrode of Ti3C2 MXene material obtained through this molten salt synthesis method delivers a Li+ storage capacity up to 738 C g-1 (205 mAh g-1) with high-rate performance and pseudocapacitive-like electrochemical signature in 1M LiPF6 carbonate-based electrolyte. MXene prepared from this molten salt synthesis route offer opportunities as high-rate negative electrode material for electrochemical energy storage applications.