In Situ Construction of Bimetallic Selenides Heterogeneous Interface on Oxidation-Stable TiCT MXene Toward Lithium Storage with Ultrafast Charge Transfer Kinetics.

TiCT (MXene) is widely acknowledged as an excellent substrate for constructing heterogeneous structures with transition metal chalcogenides (TMCs) for boosting the electrochemical performance of lithium-ion storage. However, conventional synthesis strategies inevitably lead to poor electrochemical charge transfer due to TiCT-derived TiO at the heterogeneous interface between TiCT and TMCs. Here, an innovative in situ selenization strategy is proposed to replace the originally generated TiO on TiCT with metallic TiSe interphase, clearing the bottleneck of slow charge transfer barrier caused by MXene oxidation. The construction of bimetallic selenide formed by CoSe and TiSe generates intrinsic electric fields to guide the fast ion diffusion kinetics in a heterogeneous interface. Additionally, the CoSe/TiSe/TiCT heterogeneous structure with enhanced structural stability and improved rate performance is confirmed by both experiments and theoretical calculations. The engineered heterogeneous structure exhibits an ultra-high pseudocapacitance contribution (73.1% at 0.1 mV s), rendering it well-suited to offset the kinetics differences between double-layer materials. The assembled lithium-ion capacitor based on CoSe/TiSe/TiCT possesses a high energy density and an ultralong life span (89.5% after 10 000 times at 2 A g). This devised strategy provides a feasible solution for utilizing the performance advantages of MXene substrates in lithium storage with ultrafast charge transfer kinetics.