A flexible design strategy to modify Ti3C2Tx MXene surface terminations via nucleophilic substitution for long-life Li-S batteries

Abstract

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 (SN) strategy to modify the Ti3C2Tx surface terminations and purposefully designed Magnolol-modified Ti3C2Tx (M-Ti3C2Tx) 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-Ti3C2Tx electrode could effectively suppress the lithium polysulfides shuttling via chemisorption and CS covalent bond formation. Besides, the Magnolol-modified Ti3C2Tx significantly accelerates polysulfide redox reaction and reduces the activation energy of Li2S decomposition. As a result, the as-prepared M-Ti3C2Tx 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.