Preparation and Properties of N-Doped C@SnO ₂ /Sn Particles Wrapped in a CNT Network with High Initial Coulomb Efficiency for Li-Ion Batteries

SnO2 is the most widely used high-capacity anode material in lithium-ion batteries (LIBs). However, the huge volume expansion during Li+ de-embedding, leading to structural instability and slow electrochemical kinetics, has prevented its practical application. Herein, we report a successful synthesis of ultrafine SnO2 nanoparticles by a green and efficient supercritical hydrothermal synthesis, followed by the preparation of composites consisting of nitrogen-doped amorphous carbon and carbon nanotubes (CNTs) in SnO2 (N-CNT/C@SnO2–Sn), forming a conductive network by water/solvent heating and sintering. Compared to CNT@SnO2, C@SnO2–Sn, CNT/C@SnO2–Sn, and unmodified SnO2, the results show that the heteroatom nitrogen-doped carbon and CNT materials are favorable for enhancing the electrical conductivity and structural stability of SnO2, as well as the composite has higher specific capacity, cycling reversibility, and fast electrochemical kinetics. The composite exhibits excellent lithium storage performance with a high reversible capacity of 643.9 mAh g–1, a high initial Coulombic efficiency of about 80.3% at a current density of 100 mA g–1 after 400 cycles, and a reversible capacity of 538.8 mAh g–1 even at 1 A g–1 after 500 cycles. The excellent electrochemical properties of this composite provide a reasonable guide for applying metal oxides in anode materials for LIBs.