Molecularly Tethered Conductive Network Overcomes Capacity-Stability Trade-Off of Silicon Anodes

Silicon is a premier anode candidate for next-generation lithium-ion batteries, yet its practical application is fundamentally impeded by colossal volumetric expansion and sluggish charge transport. While graphitic carbon nitride (g-C3N4) offers abundant lithiophilic sites as a buffering matrix, its inherent insulating nature and weak van der Waals interactions with Si inevitably lead to rapid structural degradation. Herein, we report a low-temperature molten salt-assisted magnesiothermic reduction strategy that enables the construction of conductive carbon nitride@silicon (CCN@Si) hybrid anodes featuring molecularly tethered interfaces. The AlCl3 molten salt acts as a unique molten-salt thermal-buffering medium that kinetically freezes Si nanoparticle growth. Concurrently, synchronized magnesiothermic denitridation (MD) triggers a critical insulator-to-conductor transition by restoring the delocalized π-conjugated carbon network. Crucially, this in situ process generates active surface dangling bonds, driving the spontaneous thermodynamic self-assembly of strong Si-C covalent bonds at the heterointerface. Both experimental characterizations and theoretical calculations confirm that this robust interfacial tethering effectively buffers volumetric strain and ensures high-flux, bidirectional electron conduction. Consequently, the CCN@Si anode exhibits exceptional electrochemical stability, delivering a high reversible capacity of 1277.0 mAh g-1 after ultralong 2000 cycles at 2 A g-1. This defect-driven molecularly tethered paradigm offers a generalizable pathway for developing ultrastable energy storage systems.