Room-temperature liquid-plasma-engineered covalent interfaces enable dual-confinement silicon anodes with ultrahigh Si content and ultralong cycling life

Silicon (Si) is widely regarded as a leading high-capacity anode candidate for next-generation lithium-ion batteries (LIBs), benefiting from its ultrahigh theoretical specific capacity and ultralow lithiation potential. However, its practical commercialization has long been impeded by severe volume variation over successive lithiation/delithiation cycles, which causes electrode pulverization, unregulated solid electrolyte interphase (SEI) growth, and consequent rapid capacity degradation. In this work, we develop a room-temperature liquid-phase plasma strategy to engineer interfacial covalent bonding in dual-confinement Si anodes with long-cycle stability. The liquid-phase plasma process produces abundant oxidative radicals and high-energy electrons, which simultaneously promote robust covalent coupling between composite components and enable in situ conformal growth of an amorphous TiO 2 interlayer on Si nanoparticles. This design constructs a hierarchical dual-confinement architecture in which Si−O−Ti covalent bonds act synergistically with physical encapsulation. This synergy effectively mitigates cycle-induced mechanical stress, preserves the structural integrity of the Si@TiO 2 @MXene electrode, and simultaneously balances electron and ion transport. Consequently, the optimized 60 wt% Si anode delivers an initial discharge capacity of 2784 mAh g −1 at 0.1 A g −1 , paired with an initial Coulombic efficiency (ICE) of 89.2%. It retains 931.4 mAh g −1 of reversible capacity after 1000 continuous cycles at 1 A g −1 , indicating improved cycling durability relative to Si-based anodes with non-covalent interfaces. The proposed liquid plasma-enabled strategy provides a versatile interfacial engineering approach for fabricating durable, high-capacity Si-based anodes for high-energy LIBs.