Heteroanionic Halogenated TiBT_x MBene Protective Layer With Dual-Functional Zincophilic and Hydrophobic Characteristics for Dendrite-Free Zinc Anode

Two-dimensional (2D) hexagonal transition metal borides (h-MBenes), emerging members of 2D materials, demonstrate significant potential as protective layers for metal anodes. However, conventional MBenes synthesized by wet etching have massive oxygen-containing terminations imported during the chemical synthesis process, with zincophobic and hydrophilic, resulting in severe dendrite growth kinetics and compromising electrode performance. In this study, we report a novel hetero-halogen TiBT_X (T_X = Cl and I) h-MBenes through a halogen-radius-isomerization strategy, enabling precise mixed-halogen functionalization to create an ultrahigh zincophilic and hydrophobic microenvironment. Compared to single -I terminations, the mixed-halogen TiBT_X exhibits significantly enhanced zincophilicity with ordered Zn²⁺ adsorption, attributed to the asymmetry-inductive effect of the larger-radius -I ions. Simultaneously, the -Cl moieties serve as a protective barrier, mitigating water-induced corrosion of the Zn anode in aqueous electrolytes. Notably, the dual-functional TiBT_x-31 layer (TiBI_0.32Cl_0.13) demonstrates exceptional electrochemical performance, achieving a prolonged cycling life exceeding 2000 h an impressive average coulombic efficiency of 99.86%. Furthermore, the TiBT_x-31@Zn||NVO full pouch cell maintains 95.3% capacity retention over 100 cycles. This work highlights the innovative halogen-radius-isomerization approach for interfacial engineering by tailoring halogen terminations, offering new insights for the development of high-performance h-MBenes-based energy storage devices.