Constructing Built-in Electric Field in Heterogeneous Flower-Like SnS2@Few-Layer Ti3C2 for Enhanced Charge Transfer Kinetics in Lithium-ion Capacitors

Lithium-ion capacitors (LICs) are considered promising advanced energy storage devices due to their combination of high energy and power density. However, the inherent mismatch in charge storage rate between anode and cathode has forced search for anode materials with accelerated reaction kinetics. Herein, heterogeneous flower-like SnS₂@few-layer Ti₃C₂ (SnS₂@f-Ti₃C₂) composites with asymmetric charge distribution through Sn─O─Ti bonded are prepared, which can regulate the electronic structure of active sites. Moreover, the presence of f-Ti₃C₂ substrate suppresses the volume expansion of SnS₂, while the SnS₂ alleviates the interlayer stacking and increases the active sites of f-Ti₃C₂ during charging/discharging processes. Consequently, LICs consisting of SnS₂@f-Ti₃C₂ anode and activated carbon (AC) cathode display high power density (6.67 kW kg⁻¹), high energy density (126.26 Wh kg⁻¹), and superior stability. Furthermore, the density functional theory (DFT) calculations and experimental characterizations reveal that the built-in electric field, induced by modulating the work function of SnS₂ and f-Ti₃C₂ MXene, enables the directional electron transfer between heterogeneous interfaces, thereby lowering the diffusion energy barrier of Li ions and boosting the electrochemical reaction kinetics of SnS₂@f-Ti₃C₂ composites. This work provides guidance for designing composites with unique surface-interface structures and modulating directional carrier transport between heterojunctions.