Borate‐Like Terminations Strengthen MXene–Silicon Coupling for Ultrafast and Durable Lithium Storage

ABSTRACT Surface terminations play a crucial role in determining the properties of MXene. This study developed a silicon anode composite using borate‐terminated MXene (Ti 3 C 2 T x ) nanosheets to achieve enhanced electrochemical performance. These borate‐like surface terminations (Ti─O─B─O) chemically anchored the MXene to Si nanoparticles, forming strong interfacial bonds. X‐ray absorption spectroscopy confirmed that borate functionalization increased the oxidation state of Ti while maintaining the local coordination environment and two‐dimensional carbide structure of the MXene, despite modification in surface chemistry. Ex‐situ XPS analysis of the borate‐terminated MXene nanosheets (B‐MXNS)/Si electrode further reveals the formation of a boron‐rich, fluorine‐regulated solid–electrolyte interphase containing B–F and P–F species with suppressed excessive LiF accumulation, indicating effective HF scavenging and mitigation of continuous electrolyte decomposition. This chemically stabilized interphase rationalizes the higher initial Coulombic efficiency and exceptional long‐term cycling stability of the B‐MXNS/Si anode at high silicon loading. The composite (60 wt% Si) retained around 80% of the initial capacity after 1200 cycles at 2 A g −1 and delivered approximately 2100 mAh g −1 at 4 A g −1 . This study underscores that atomic‐level surface engineering with boron effectively addresses long‐standing challenges in high‐silicon‐content anodes and provides a promising route toward high‐energy‐density lithium‐ion batteries with extended cycle life.