Carbon Nanotube-Reinforced Binder-Free Sn/SnO₂/Cu₃Sn Composite Materials for High-Capacity Lithium-Ion Battery Anodes

Tin (Sn)-based anodes have been extensively studied because of the abundant reserves, low cost of Sn, high theoretical capacity and ideal working voltages. However, the Li⁺ insertion/deinsertion process induces huge volume changes, leading to pulverization of the active particles, limiting their commercial application. Therefore, in this work, an Sn/SnO₂/Cu₃Sn/CNTs composite anode material with a three-dimensional (3D) conductive network structure was synthesized by electrodeposition on a copper (Cu) collector. The results showed that when used as an anode in a lithium-ion battery (LIB), the Sn/SnO₂/Cu₃Sn/CNTs sample retained a reversible specific capacity of 779 mAh/g after 200 cycles, whereas a Sn/SnO_2/Cu₃Sn sample retained only 367 mAh/g after 100 cycles. Moreover, the Sn/SnO₂/Cu₃Sn/CNTs sample retained a capacity of 553 mAh/g even after 500 cycles at 1C. The Li⁺ diffusion coefficient of the Sn/SnO₂/Cu₃Sn/CNTs sample was calculated as 2.82 × 10^-12 cm² s^-1, almost four times higher than that of the Sn/SnO₂/Cu₃Sn sample (7.45 × 10^-13 cm² s^-1). The is because the CNTs conductive network is effective in mitigating the stress changes caused by volume expansion of the composite during Li⁺ insertion/deinsertion, which improves electronic conductivity and reduces Li⁺ diffusion resistance. This work provides a viable approach for designing anodes with high power density.