No abstract

Silicon-based materials are the desirable anodes for next-generation lithium-ion batteries; however, the large volume change of Si during the charging/discharging process causes electrode fracture and an unstable solid–electrolyte interphase (SEI) layer, which severely impair their stability and Coulombic efficiency. Herein, a bundle of silicon nanoparticles is encapsulated in robust micrometer-sized MXene frameworks, in which the MXene nanosheets are precrumpled by 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-cross-linking 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 SEI layer outside the frameworks upon cycling, which not only shuts down the parasitic reaction between Si and an 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 mA h 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.

The high-capacity silicon anode is regarded as a promising electrode material for next-generation lithium-ion batteries. Unfortunately, its practical application is still severely hindered by electrode fracture and unstable solid electrolyte interphase during cycling. Herein, we design a structure of encapsulating silicon in a robust “janus shell”, in which an internal graphene shell with sufficient void space is used to absorb the mechanical stress induced by volume expansion, and the conformal carbon outer shell is introduced to strongly bond the loosely stacked graphene shell and simultaneously seal the nanopores on the surface. With the ultrastable janus carbon shell, the excellent structural integrity of the electrode and stable solid electrolyte interphase layer could be effectively preserved, resulting in an impressive cycling behavior. Indeed, the as-synthesized anodes demonstrate superior cycle stability and excellent rate performance, delivering a high reversible capacity of 1416 mA h g–1 at a current density of 0.2 A g–1 and 852 mA h g–1 at a high current density of 5 A g–1. Remarkably, the superior capacity retention of 88.5% could be achieved even after 400 cycles at a high current density of 2 A g–1. More importantly, this work opens up a novel avenue to address high-capacity anodes with a large volume change.

No abstract

No abstract