A flexible design strategy to modify Ti3C2T MXene surface terminations via nucleophilic substitution for long-life Li-S batteries

An efficient nucleophilic substitution strategy is reported to purposefully designed Magnolol-modified Ti 3 C 2 T x (M-Ti 3 C 2 T x ) as high affinitive and superior reaction kinetics cathode host materials. MXene-based materials have gained considerable attention for lithium-sulfur (Li-S) batteries cathode materials due to their superior electric conductivity and high affinitive to polysulfides. However, there are still challenges in modifying the surface functional groups of MXene to further improve the electrochemical performance and increase the structure variety for MXene-based sulfur host. Herein, we report an efficient and flexible nucleophilic substitution (S N ) strategy to modify the Ti 3 C 2 T x surface terminations and purposefully designed Magnolol-modified Ti 3 C 2 T x (M-Ti 3 C 2 T x ) as powerful cathode host materials. Benefiting from more C–Ti–O bonds forming and diallyl groups terminations reducing after the dehalogenation and nucleophilic addition reactions, the given M-Ti 3 C 2 T x electrode could effectively suppress the lithium polysulfides shuttling via chemisorption and C S covalent bond formation. Besides, the Magnolol-modified Ti 3 C 2 T x significantly accelerates polysulfide redox reaction and reduces the activation energy of Li 2 S decomposition. As a result, the as-prepared M-Ti 3 C 2 T x electrode displays an excellent rate capability and a high reversible capacity of 7.68 mAh cm −2 even under 7.2 mg cm −2 S-loaded with a low decay rate of 0.07% (from 2nd cycle). This flexible surface-modified strategy for MXene terminations is expected to be extended to other diverse MXene applications.