Opening Magnesium Storage Capability of Two-Dimensional MXene by Intercalation of Cationic Surfactant

Abstract

Two-dimensional (2D) Ti3C2 MXene has attracted great attention in electrochemical energy storage devices (supercapacitors and lithium-ion and sodium-ion batteries) due to its excellent electrical conductivity as well as high volumetric capacity. Nevertheless, a previous study showed that multivalent Mg2+ ions cannot reversibly insert into MXene, resulting in a negligible capacity. Here, we demonstrate a simple strategy to achieve high magnesium storage capability for Ti3C2 MXene by preintercalating a cationic surfactant, cetyltrimethylammonium bromide (CTAB). Density functional theory simulations verify that intercalated CTA+ cations reduce the diffusion barrier of Mg2+ on the MXene surface, resulting in the significant improvement of the reversible insertion/deinsertion of Mg2+ ions between MXene layers. Consequently, the MXene electrode exhibits a desirable volumetric specific capacity of 300 mAh cm–3 at 50 mA g–1 as well as outstanding rate performance. This work endows MXene material with an application in electrochemical energy storage and, simultaneously, introduces magnesium battery materials as a member.

MXene‐Based Anodes for Metal‐Ion Batteries

“…To fully exploit the entire MXene sheet, sufficient interlayer space must be provided for metal plating, and the intercalation barrier of deep adsorption sites must be lowered (especially in the case of large Na + and K + ions) by either delamination or expansion of the interlayer spacing (i. e., pillaring). Interlayer expansion and delamination is easily achieved in situ during MAX phase etching by LiF/HCl solution, but it has also been demonstrated in HF‐etched MXenes through intercalation of molecules and larger ions such as DMSO and K + . Restacking can be prevented by thoroughly homogenising the components in MXene composites, or by the fabrication of a 3D meso‐ or macroporous design.…”

“…The first was made using cetyltrimethylammonium bromide (CTAB) to increase the interlayer spacing of Ti 3 C 2 T X stacks, and the second was made by hydrothermally compositing Ti 3 C 2 T X with MoS 2 (another suitable cathode material for Mg cells) . Both of these cathodes dramatically increased the amount of Mg 2+ intercalated into Ti 3 C 2 T X , with the pre‐intercalation of CTAB/CTA + into delaminated Ti 3 C 2 T X achieving a capacity of 47–108 mAh g −1 at 50–2000 mA g −1 . The Ti 3 C 2 T X /MoS 2 composite exhibited a reasonable plateau in its galvanometric discharge curve, and delivered 93–165 mAh g −1 at 50–200 mA g −1 , but only retained 70 % of that after 50 cycles…”

Prelithiated V2C MXene: A High‐Performance Electrode for Hybrid Magnesium/Lithium‐Ion Batteries by Ion Cointercalation

“…MXenes, a novel kind of 2D layered transition‐metal carbides or nitrides, have recently attracted tremendous attention in many fields such as energy storage, catalysis, electronics, etc. Especially, MXenes with unique physical and chemical properties become excellent candidates for battery electrode materials .…”

Are MXenes suitable as cathode materials for rechargeable Mg batteries?

“…38 Recently, several works have reported similar initial capacities for pristine Ti3C2Tx, all tested with APC-THF electrolyte at room temperature. [39][40][41] By pre-incorporation of large organic molecules (e.g. cationic surfactant, 40 phenyl-MgCl from the electrolyte 41 ) or even carbon nanospheres, 39 reversible capacities of 100-200 mA h g -1 have been reported.…”

“…[39][40][41] By pre-incorporation of large organic molecules (e.g. cationic surfactant, 40 phenyl-MgCl from the electrolyte 41 ) or even carbon nanospheres, 39 reversible capacities of 100-200 mA h g -1 have been reported. However, all the mentioned works have utilized delaminated Ti3C2Tx, and combined with the mentioned spacer molecules/structures, a highly porous structure with a large surface area is obtained.…”