Fluorine- and Acid-Free Strategy toward Scalable Fabrication of Two-Dimensional MXenes for Sodium-Ion Batteries

Abstract

MXenes are emerging 2D materials that have gained great attention because of their unique physical−chemical properties. However, the wide application of MXenes is prohibited by their high cost and environmentally harmful synthesis process. Here a fluoride-and acid-free physical vacuum distillation strategy is proposed to directly synthesize a series of MXenes. Specifically, by introducing a low-boiling-point element into MAX and subsequently evaporating A elements via physical vacuum distillation, fluoride-free MXenes (Ti 3 C 2 T x , Nb 2 CT x , Nb 4 C 3 T x , Ta 2 CT x , Ti 2 NT x , Ti 3 CNT x , etc.) are fabricated. This is a green and one-step process without any acid/alkaline involved and with all reactions inside a vacuum tube furnace, avoiding any contamination to external environments. Besides, the synthetic temperature is controlled to regulate the layered structures and specific surface areas of MXenes. Accordingly, the synthesized Ti 3 C 2 T x MXene exhibits improved sodium storage performance. This method may provide an alternative for the scalable production of MXenes and other 2D materials.

Two-dimensional MXenes for flexible energy storage devices

“…designed a physical vacuum distillation to synthesize a series of MXenes. 56 By regulating vacuum temperature, Al atoms in MAX precursor were replaced by Zn atoms in ZnCl 2 molten salt. Subsequently, it was evaporated by forming AlCl 3 at low temperature.…”

Cobalt Oxide 2D Nanosheets Formed at a Polarized Liquid|Liquid Interface toward High-Performance Li-Ion and Na-Ion Battery Anodes

“…Methods that yield nanostructured active materials, such as using an ITIES, are useful in battery research as small active particles give porous electrodes with high capacity and excellent rate performance. − In particular, using active particles in the form of 2D platelets has an advantage over spherical particles because they possess three times less surface area per volume for a given solid-state diffusion length. , This gives short diffusion lengths, and so reduced solid-state diffusion times and enhanced rate performance, without extremely large active surface areas. In this manner, unwanted parasitic reactions are reduced between the active electrode materials and the nonaqueous electrolyte at different potentials …”

Buffer solution induced highly crystalline sodium-rich Prussian blue for sodium storage

“…Rechargeable sodium ion batteries (SIBs) are recognized as promising candidates for large-scale energy-storage applications. [1][2][3][4][5][6][7][8] Prussian blue (PB) and its analogs (PBAs) have gained a lot of attention as the cathode of SIBs benefiting from their rigid open-framework and large interstitial sites, which allows the fast insertion and extraction of sodium ions during the charge/discharge process. [9][10][11] Among these PBAs, the Na 2Àx Fe[Fe(CN) 6 ] 1Ày & y ÁnH 2 O is most likely to be used in SIBs due to its high theoretical capacity of 170 mA h g À1 , relatively high voltage around 3.2 V and low cost.…”