Improved lithium ion storage performance of Ti₃C₂T_x MXene@S composite with carboxymethyl cellulose binder

MXenes are regarded as promising electrode materials for lithium-ion batteries owing to their high electrical conductivity and two-dimensional structure but suffer from low intrinsic specific capacities. In this study, we fabricate sulphur-doped multilayer Ti₃C₂T_x MXenes via calcination and annealing using sublimed sulphur as the sulphur source. After sulphur doping, the interlayer spacing of Ti₃C₂T_x increases, which is favourable for Li-ion insertion. The Ti₃C₂T_x MXene@S composite exhibits excellent electrochemical performance. A high reversible specific capacity of 393.8 mAh g^-1 at a current density of 100 mA g^-1 after 100 cycles is obtained. Additionally, a negative fading phenomenon is observed when the specific capacity increases to 858.9 mAh g^-1 after 2550 cycles at 1 A g^-1 and to 322.2 mA h g^-1 after 3600 cycles at 5 A g^-1 from the initial 267.3 mAh g^-1. We systematically investigate the effects of two different binders (polyvinylidene difluoride and carboxymethyl cellulose, hereinafter abbreviated as PVDF and CMC, respectively) on the electrochemical performance of the Ti₃C₂T_x MXene@S composite and discovered that the electrode using the CMC binder exhibits better lithium-ion storage performance than that using the PVDF binder, which is attributed to the lower charge transfer resistance, higher ion diffusivity, and enhanced adhesion force.