Rational Design of Porous N-Ti3C2 MXene@CNT Microspheres for High Cycling Stability in Li–S Battery

Abstract

Highlights

• N-Ti₃C₂@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-Ti₃C₂@CNT microsphere/S cathode shows highly cycling stability in lithium-sulfur battery.

Herein, N-Ti₃C₂@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-Ti₃C₂@CNT microspheres to be ideal sulfur host. When used in lithium–sulfur (Li–S) battery, the N-Ti₃C₂@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 C-rate 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.