MXene Frameworks Promote the Growth and Stability of LiF-Rich Solid-Electrolyte Interphases on Silicon Nanoparticles Bundles.

The silicon-based materials are the desirable anodes for next-generation lithium-ion batteries; however, the large volume change of Si during charging/discharging process causes electrode fracture and unstable solid-electrolyte interphase (SEI) layer, which severely impair its stability and Coulombic efficiency. Herein, the bundle of silicon nanoparticles are encapsulated in the robust micrometer-sized MXene frameworks, in which the MXene nanosheets are pre-crumpled by the capillary compression force to effectively buffer the stress induced by the volume change, and the abundant covalent bonds (Ti-O-Ti) between adjacent nanosheets formed through a facile thermal self-crosslinking reaction further guarantee the robustness of the MXene architecture. Both factors stabilize the electrode structure. Moreover, the abundant fluorine terminations on MXene nanosheets contribute to an in situ formation of a highly compact, durable and mechanically robust LiF-rich solid-electrolyte interphase layer outside the frameworks upon cycling, which not only shuts down the parasitic reaction between Si and organic electrolyte but also enhances the structural stability of MXene frameworks. Benefiting from these merits, the as-prepared anodes deliver a high specific capacity of 1797 mAh g-1 at 0.2 A g-1, and a high capacity retention of 86.7% after 500 cycles at 2 A g-1 with an average Coulombic efficiency of 99.6%. Significantly, this work paves the way for other high-capacity electrode materials with a strong volume effect.