# The Effect of TiO2 on the Electrochemical Performance of Sb2O3 Anodes for Li-Ion Batteries
## 3 Results and Discussion
### Electrochemical Performance  
Figure 8 shows the cyclic voltammetry (CV) curves of the initial five cycles for the TiO\({}_{2}\), Sb\({}_{2}\)O\({}_{3}\) and TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) electrodes at a scanning rate of 0.1 mVs\({}^{-1}\) between 0.01 and 3.0 V (vs. Li\({}^{+}\)/Li) The CV profiles of pure TiO\({}_{2}\) (Figure 8A) show similar results to those observed in previous work [63; 64; 65]. As shown in Figure 8B, the CV profiles of the Sb\({}_{2}\)O\({}_{3}\) electrode show that the first cathodic scan is different form the subsequent cathodic cycles, which can be attributed to the formation of the solid electrolyte interface (SEI) layer. The two cathodic peaks at 1 V and 0.6 V could be attributed to the conversion process from Sb\({}_{2}\)O\({}_{3}\) to metallic Sb and to the formation of the Li\({}_{3}\)Sb during the alloying reaction process, respectively [31]. The peaks from the 1 st to the 5 th cycles in the anodic scan, located at 1.1 V and 1.3 V, correspond to the dealloying and delithiation reactions. These CV results are in agreement with those reported on the Sb\({}_{2}\)O\({}_{3}\) electrodes [31; 66]. The CV results of the TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) electrode (Figure 8C) show that at the first cathodic scan, a distinct peak at 1.71 V indicated the transition of Sb\({}_{2}\)O\({}_{3}\) to metallic Sb and Li\({}_{2}\)O (as shown in Equation (1). In the subsequent cathodic scans, a weak reduction peak was observed at 2.5 V, indicating the transformation of Sb\({}_{2}\)O\({}_{3}\) to Sb metal. The reduction peaks at 0.44 and 1.07 V can be \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Energy** & **Ti** & **Energy** & **Ti** & **Energy** & **O** & **Energy** & **Sb** \\  & **(eV)** & **2p\({}_{\text{2/2p}}\)** & **(eV)** & **Ti** & **(eV)** & **1 s** & **(eV)** & **3d\({}_{\text{3/2}}\)/3d\({}_{\text{3/2}}\)** \\ \hline \multirow{2}{*}{(A) TiO\({}_{2}\)} & 458.6/464.3 & Ti\({}^{+}\)-O & 471.9 & Satellite & 530.4 & O-Ti & N/A & \\  & & & & & & & & \\ \hline \multirow{2}{*}{(B) TiO\({}_{2}\)@Sb\({}_{2}\)O\({}_{3}\) 3.1} & 458.6/464.4 & Ti\({}^{+}\)-O & 471.9 & Satellite & 531.4 & O-M & 528.4/537.7 & Sb(0) \\  & & & & & & & & 530.7/540.4 & Sb\({}^{3+}\)-O \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of the XPS fittings of the synthesized TiO\({}_{2}\) nanoparticles at 175 \({}^{\circ}\)C (A) and the TiO\({}_{2}\)@Sb\({}_{2}\)O\({}_{3}\) 3:1 (B). Figure 7: XPS spectrum of O 1S of the TiO\({}_{2}\) synthesized hydrothermally at 175 \({}^{\circ}\)C (**A**) and the Sb3d for 3:1 TiO\({}_{2}\) /Sb\({}_{2}\)O\({}_{3}\) (**B**). The bleu, green and red lines are the fitting curves of the XPS results shown in the Figure. attributed to a series of electrochemical reactions, including the alloying of metallic Sb to Li\({}_{x}\)Sb and the formation of the SEI layer at the surface of the electrode that is caused by the electrolyte decomposition [34; 49; 67]. After the 1 st cycle, these two peaks, at 1.71 and 0.44 V, were reversible and shifted slightly to the higher voltages, indicating the formation of a stable SEI film during the first cathodic scan [68]. This shift signified that the material was gradually activating as lithium was being deposited via insertion, which simultaneously increased the voltage. The CV profile of the (3:1) TiO\({}_{2}\)/Sb\({}_{2}\)O\({}_{3}\) electrode shows complex redox reactions, indicating an activation process in the initial lithiation process that was also observed in the literature [67; 68]. The CV results of different TiO\({}_{2}\) to Sb\({}_{2}\)O\({}_{3}\) ratios (1:1 and 1:4) are shown in the SI file Fig (Sx). The CV profiles clearly indicate that on increasing the Sb\({}_{2}\)O\({}_{3}\) amount in the composite electrode, the reactions and alloying/dealloying of Sb take place at below 1 V. Also, the formation of Sb\({}_{5}\)O\({}_{4}\)Cl\({}_{2}\) after heat treatment can also result in a complex CV profile of the composite electrode.