Interfacial built-in electric field and crosslinking pathways enabling WS₂/Ti₃C₂T_x heterojunction with robust sodium storage at low temperature

Developing efficient energy storage for sodium-ion batteries (SIBs) by creating high-performance heterojunctions and understanding their interfacial interaction at the atomic/molecular level holds promise but is also challenging. Besides, sluggish reaction kinetics at low temperatures restrict the operation of SIBs in cold climates. Herein, cross-linking nanoarchitectonics of WS₂/Ti₃C₂T_x heterojunction, featuring built-in electric field (BIEF), have been developed, employing as a model to reveal the positive effect of heterojunction design and BIEF for modifying the reaction kinetics and electrochemical activity. Particularly, the theoretical analysis manifests the discrepancy in work functions leads to the electronic flow from the electron-rich Ti₃C₂T_x to layered WS₂, spontaneously forming the BIEF and “ion reservoir” at the heterogeneous interface. Besides, the generation of cross-linking pathways further promotes the transportation of electrons/ions, which guarantees rapid diffusion kinetics and excellent structure coupling. Consequently, superior sodium storage performance is obtained for the WS₂/Ti₃C₂T_x heterojunction, with only 0.2% decay per cycle at 5.0 A g⁻¹ (25 °C) up to 1000 cycles and a high capacity of 293.5 mA h g⁻¹ (0.1 A g⁻¹ after 100 cycles) even at −20 °C. Importantly, the spontaneously formed BIEF, accompanied by “ion reservoir”, in heterojunction provides deep understandings of the correlation between structure fabricated and performance obtained.