MXene/Si@SiO_<i>x</i>@C Layer-by-Layer Superstructure with Autoadjustable Function for Superior Stable Lithium Storage

Abstract

Despite its very high capacity (4200 mAh g–1), the widespread application of the silicon anode is still hampered by severe volume changes (up to 300%) during cycling, which results in electrical contact loss and thus dramatic capacity fading with poor cycle life. To address this challenge, 3D advanced Mxene/Si-based superstructures including MXene matrix, silicon, SiOx layer, and nitrogen-doped carbon (MXene/Si@SiOx@C) in a layer-by-layer manner were rationally designed and fabricated for boosting lithium-ion batteries (LIBs). The MXene/Si@SiOx@C anode takes the advantages of high Li+ ion capacity offered by Si, mechanical stability by the synergistic effect of SiOx, MXene, and N-doped carbon coating, and excellent structural stability by forming a strong Ti–N bond among the layers. Such an interesting superstructure boosts the lithium storage performance (390 mAh g–1 with 99.9% Coulombic efficiency and 76.4% capacity retention after 1000 cycles at 10 C) and effectively suppresses electrode swelling only to 12% with no noticeable fracture or pulverization after long-term cycling. Furthermore, a soft package full LIB with MXene/Si@SiOx@C anode and Li[Ni0.6Co0.2Mn0.2]O2 (NCM622) cathode was demonstrated, which delivers a stable capacity of 171 mAh g–1 at 0.2 C, a promising energy density of 485 Wh kg–1 based on positive active material, as well as good cycling stability for 200 cycles even after bending. The present MXene/Si@SiOx@C becomes among the best Si-based anode materials for LIBs.