Abstract: PAN-ACF/SnO₂ composites were synthesized by a Sol-Gel method using SnCl₂ and polyacrylonitrile- based activated carbon fiber (PAN-ACF) as raw materials, and electrochemical performance of the composites as negative electrodes for lithium ion batteries was investigated. The chemical composition and micro-structure of the composites were examined with X-ray diffraction (XRD). The structure features of PAN-ACF and PAN-ACF/SnO₂ composites were analyzed by scanning electron microscope (SEM). The mass fraction of SnO₂ was determined by thermo gravimetric analysis (TGA). The electrochemical properties of the composites were evaluated by galvanostatic charge-discharge, electrochemical impedance spectrum (EIS) and cyclic voltammetry (CV). The results indicate that SnO₂ mass fraction in the PAN-ACF/SnO₂ composites has certain influence on the morphology, structure and electrochemical performance of the product. The SnO₂ in the composites has a tetragonal rutile structure with lattice constants of a = 0.4739 nm and c = 0.3181 nm. There are no obvious changes happened on the surface of PAN-ACF after charging and discharging process. When the composites are used as negative material for lithium ion batteries, the initial discharge capacity of composites with SnO₂ mass fraction of 41.9% is up to 1824 mAh/g at current density of 50 mA/g, which remains 450 mAh/g after 20 cycles and tends to be stable, showing a good cycling performance.

Key words: PAN-based activated carbon fiber, tin oxide, lithium-ion battery, negative material