HIGHLIGHTS • N-Ti 3 C 2 @CNT microspheres are successfully synthesized by the simple spray drying and one-step pyrolysis. • Within the microsphere, MXene nanosheets intimately interact with CNTs constructing porous and highly conductive network, which can provide strong immobilization for polysulfides. • N-Ti 3 C 2 @CNT microsphere/S cathode shows highly cycling stability in lithium-sulfur battery. ABSTRACT Herein, N-Ti 3 C 2 @CNT microspheres are successfully synthesized by the simple spray drying method. In the preparation process, HCl-treated melamine (HTM) is selected as the sources of carbon and nitrogen. It not only realizes in situ growth of CNTs on the surface of MXene nanosheets with the catalysis of Ni, but also introduces efficient N-doping in both MXene and CNTs. Within the microsphere, MXene nanosheets interconnect with CNTs to form porous and conductive network. In addition, N-doped MXene and CNTs can provide strong chemical immobilization for polysulfides and effectively entrap them within the porous microspheres. Above-mentioned merits enable N-Ti 3 C 2 @CNT microspheres to be ideal sulfur host. When used in lithium-sulfur (Li-S) battery, the N-Ti 3 C 2 @CNT microspheres/S cathode delivers initial specific capacity of 927 mAh g −1 at 1 C and retains high capacity of 775 mAh g −1 after 1000 cycles with extremely low fading rate (FR) of 0.016% per cycle. Furthermore, the cathode still shows high cycling stability at high Crate of 4 C (capacity of 647 mAh g −1 after 650 cycles, FR 0.027%) and high sulfur loading of 3 and 6 mg cm −2 for Li-S batteries.
MXenes
have gained great attention in various fields because of
their fascinating properties; however, the preparation of few-layered
MXene powders is still limited by serious restacking of MXene nanosheets.
Herein, for the first time, we have demonstrated an effective ammonium
ion route to fundamentally address restacking and aggregation of the
MXene nanosheets, using a solution-phase flocculation method (NH4+ method and modified NH4+ method) for large-scale
preparation of few-layered Ti3C2T
x
MXene powders in large quantities. The as-prepared
few-layered MXene nanosheet powders show large size in the ab plane without the restacking phenomenon even at scanning
electron microscopy measurements of 400× magnification, demonstrating
the effectiveness of the proposed method. The method is also suitable
for large-scale synthesis of other few-layered MXene powders, including
Nb4C3T
x
, V2CT
x
, Nb2CT
x
, etc., providing a general approach for the preparation of
various few-layered MXene nanosheet powders, which represents a significant
result for the development of MXenes.
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