# The Effect of TiO2 on the Electrochemical Performance of Sb2O3 Anodes for Li-Ion Batteries
## 3 Results and Discussion
### Electrochemical Performance
After the 2 nd cycle, the coulombic efficiency for all electrodes was over 99%, indicating good cycling stability and capacity retention. Noticeably, the (3:1) TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) composite electrode outperformed both materials and demonstrated a good cyclic performance, maintaining a stable specific capacity between the 30 th and 70 th cycles. And, remarkably, by the 77 th cycle its specific capacity increased to 521 mAh g\({}^{-1}\), eventually finishing at 536 mAh g\({}^{-1}\) by its 100 th cycle. It can be assumed that the thickness of the TiO\({}_{2}\) coating along the surface of the Sb\({}_{2}\)O\({}_{3}\) particles was significant enough to act as a buffer when undergoing high volume changes. Figures S3 and S4 show the charge/discharge profile and cycling performance of the TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) composite electrode with 1:1 and 1:4 ratios. The results in Figures S3 and S4 show a capacity degradation (capacity fading) caused by the high-volume change of the composite electrodes after 100 cycles at 100 mA g\({}^{-1}\). The results observed in Figures S3 and S4 on the electrochemical performance of TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) composite electrodes with lower ratios (1:4) showed much higher amounts of the Sb material and a not-sufficient amount of TiO\({}_{2}\) to observe a coating on Sb\({}_{2}\)O\({}_{3}\) particles. Figure 10: Cycling performance and coulombic efficiency of Sb\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\) and (3:1) TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) electrodes at a current density of 100 mA g\({}^{-1}\). Figure 9: Charge/discharge curves after 100 cycles of (**a**) Sb\({}_{2}\)O\({}_{3}\), (**b**) TiO\({}_{2}\) and (**c**) (3:1) TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\). The diffraction patterns of the three ratios studied in the hydrothermal synthesis are shown in the supplementary information (Figure S5). For the current work, it was desirable to perform a high level of TiO\({}_{2}\) coating on the Sb\({}_{2}\)O\({}_{3}\) particles to ensure that the volume expansion issue of the composite electrode, caused by a high amount of Sb, would be adequately addressed. The XRD results for the 1:1 ratio (Figure S5A) show some visible TiO\({}_{2}\) coating in the diffraction pattern, as indicated by the peak at 29 in 2-theta, while for the (1:4) TiO\({}_{2}\):Sb\({}_{2}\)O\({}_{3}\) sample the TiO\({}_{2}\) was not visible. To study the effect of TiO\({}_{2}\) on the Sb\({}_{2}\)O\({}_{3}\) material, one needs to have sufficient TiO\({}_{2}\) present in the sample, as without enough amount of TiO\({}_{2}\) in the composite there may only be a doping effect and not a complete encapsulation of the Sb\({}_{2}\)O\({}_{3}\) particles. The diffraction pattern of the (1:4) TiO\({}_{2}\):Sb\({}_{2}\)O\({}_{3}\) sample indicates that the TiO\({}_{2}\) phase was not visible. However, in the (1:1) TiO\({}_{2}\):Sb\({}_{2}\)O\({}_{3}\) sample, the Ti phase becomes visible in the diffraction pattern, as does the Sb\({}_{5}\)O\({}_{4}\)Cl\({}_{2}\). In fact, Sb\({}_{4}\)O\({}_{5}\)Cl\({}_{2}\) compounds were used as anode materials in LIBs, SIBs and potassium ion batteries [72]. The electrochemical performance of the Sb\({}_{4}\)O\({}_{5}\)Cl\({}_{2}\) anode in LIBs was somehow similar to that of Sb\({}_{2}\)O\({}_{3}\)[31]. To examine the rate performance of the nanocomposite electrode, Li-ion half cells were cycled at different current densities, starting at 50, 100, 200, 400, 500 and then back to 50 mA g\({}^{-1}\). Figure 11 shows the rate performance in terms of charge capacity vs cycle numbers for TiO\({}_{2}\), Sb\({}_{2}\)O\({}_{3}\) and (3:1) TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) electrodes. The Sb\({}_{2}\)O\({}_{3}\) electrode exhibited a high capacity up to the 40 th cycle, but was not steady and decreased rapidly over time, while TiO\({}_{2}\) demonstrated a stable rate performance but showed low capacity.