SiOx owing to high reversible capacity and moderate volume expansion has been attracting a lot of attention as state-of-the-art anodes for the next generation of Li-ion batteries. However, poor cycling performance and poor rate capability, respectively associated with detrimental volume expansion and insulative amorphous SiO2, are still challenging issues which need to be addressed for the actual employment as anodes for Li-ion batteries. In this regard, here we design, synthesize, characterize and test carbon coated sheet-like SiO1.1 nanocomposites formed by Si-nanodomains confined inside amorphous SiO2 (nano-Si/a-SiO2). As a proof-of-concept, we achieve sheet-like SiOx nanocomposites via in-situ transformation of delaminated siloxene. In particular, self-prepared siloxene with oxygen-inserted Si6 rings terminated with H and OH ligands is prepared by delamination of CaSi2 in dilute HCl. Importantly, the resulting carbon coated nano-Si/a-SiO2 material shows enhanced reaction kinetics and structural stability leading to 946 mAh g−1 capacity at 0.15Ag−1. Intriguingly, 38.0% (~360 mAh g−1) of the maximum capacity is maintained even at 7.5Ag−1, corresponding to a remarkable less than 3min charge/discharge time. Finally, the electrode shows merely 24% of volume expansion and minor cracks with capacity retention of 92% after 300 cycles at 7.5Ag−1.