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.