MXene
nanosheets (MNSs) with high conductivity, high flexibility,
and rich surface functional groups have gained renewed attention due
to their potential applications for energy storage devices. However,
the low theoretical specific capacity and easy self-aggregation of
MNSs severely restrict their practical application. Herein, a superior
anode material with a unique hierarchical structure and optimal composition
(SnO2@NDPC/MNSs-2, NDPC = nitrogen-doped porous carbon)
for lithium-ion capacitors (LICs) is successfully fabricated by an
electrostatic self-assembly strategy. Specifically, the contrary charges
of the SnO2@NDPC and MNSs enable a feasible and convenient
route for the preparation of the as-achieved nanocomposite. Moreover,
the SnO2@NDPC with ∼5 nm SnO2 nanoparticles
offering a high specific capacity and pores structure can simultaneously
prevent the restack of MNSs and withstand the volume expansion during
the repeated Li+ insertion–extraction processes,
and the two-dimensional MNSs can improve the overall conductivity
of the nanocomposite and facilitate the Li+ transport kinetics.
As a result, the as-prepared anode material displays excellent rate
performance and extraordinary cycle stability, with a high specific
capacity of 465 mAh g–1 after 500 cycles at 2 A
g–1 and 90.2% capacity retention capability. More
importantly, an assembled LIC with the biomass-derived nitrogen-rich
porous carbon and SnO2@NDPC/MNSs-2 as respective cathode
and anode can deliver a high energy density of 55.9 Wh kg–1 at a high power density of 6097 W kg–1 and excellent
cycle performance, making it potential an anode material for practical
LICs with high power and energy densities.