Abstract
Sn-based anode material is considered as the high energy density anode material to replace the conventional carbon anode materials. Furthermore, high structure stability of lithium titanate is also investigated to improve its electrochemical performance. For Sn-based anode materials, various morphologies of carbonaceous materials were chosen as the substrate for Sn coating by carbothermal reduction process. The morphology of carbon substrate affects the electrochemical performance of Sn-based/C composite anode material. The different morphologies of carbon materials include mesophase graphite powder (MGP), nature graphite (NG), and multi-walled carbon nanotube added with nature graphite (MWCNTs + NG). The additive of MWCNT was a crucial factor to improve Sn-based composite anodes for cyclability and reversible capacity. Volume changes and morphological changes in Sn can be reduced by encasing MWCNT in a carbonaceous material that has sufficient flexibility to act as a buffer. The charge capacity of the Sn-SnO2 / C-C (NG+MWCNT) electrode in the fiftieth cycle was 435 mAh/g, which was higher than that of the Sn/C (NG) electrode. After 50 cycles, the retention of the Sn-SnO2 / C-CNT electrode and the Sn/C electrode was 97% and 63%, respectively. Pristine Li4Ti5O12 (LTO) and Ru-doped Li4Ti5O12 (Ru-doped LTO) are synthesized by solid-state reaction. Ru doping into the lattice of LTO affects the electronic configuration of LTO, leading to the modification of optical properties and conductivity. The variations between pristine LTO and Ru-doped LTO in optical properties are investigated by UV–vis and Raman spectroscopy. The significant improvement in electrochemical performance demonstrates that ruthenium doped lithium titanate is promising as a high rate anode for lithium ion batteries. Moreover, an entanglement structure of LTO / multi-walled carbon nanotube (LTO / MWCNTs) composite was prepared by a ball-milling-assisted solid-state reaction. The additive of MWCNTs can prevent the aggregation of LTO particles during the calcination process of the solid-state reaction. In addition, the entanglement of the MWCNTs and LTO creates an effective conductive network, which improves the electrochemical performance of LTO. After 100 cycles, the reversible capacity and capacity retention of LTO / MWCNTs is 147 mAh/g and 97%, respectively, at 10 C. Finally, the as-synthesized of Ru-doped LTO / MWCNTs composite anode possesses the advantages of Ru-doping, particle size reducing, and surface conductivity improving. After 100 cycles, Ru-doped LTO / MWCNTs provide the highest reversible capacity of 156 mAh/g among the others electrode of bare LTO, Ru-doped LTO and LTO / MWCNTs at 10 C.