## 3 Results and Discussion
### Electrochemical Performance Measurement of LTO in LTO/LFP Battery  
Then, for large-scale application, the electrochemical performance of LTO material is important to be analyzed using a full-cell battery (LTO vs. LFP). The LTO/LFP battery was tested using NEWARE Battery analyzer and BTS software. First, in order to investigate the best C-rate for the formation of an LTO-LFP battery, the various C-rates were used for testing. Figure 2 presents the charge-discharge formation curve at various C-rates of an LTO-0 wt % NaCl/LFP battery with a voltage range of 1.0-3.0 V. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**LTO**} & \multirow{2}{*}{**Lattice Constant (Å)**} & \multicolumn{4}{c}{**FWHM (\({}^{\circ}\))**} & \multicolumn{4}{c}{**Crystallite Size (nm)**} \\ \cline{3-8}  & & **(111)** & **(311)** & **(400)** & **(111)** & **(311)** & **(400)** \\ \hline
0 wt \% NaCl & 8.377 & 0.321 & 0.266 & 0.272 & 26.94 & 32.72 & 32.80 \\
2 wt \% NaCl & 8.373 & 0.197 & 0.140 & 0.170 & 42.66 & 62.17 & 52.48 \\
4 wt \% NaCl & 8.362 & 0.154 & 0.137 & 0.168 & 54.57 & 63.53 & 53.11 \\
6 wt \% NaCl & 8.384 & 0.151 & 0.135 & 0.146 & 55.66 & 64.47 & 61.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The structural parameters of LTO material. The optimum initial specific capacity was operated at 0.3 C-rate, which obtained the specific discharge capacity of 121.1 mAh/g. Hence, the 0.3 C-rate was chosen for further testing of the LTO material with NaCl addition. Figure 3 presents the electrochemical performance (1.0-3.0 V) of LTO with various additions of NaCl at 0.3 C-rate. The LTO/LFP battery displayed a plateau voltage at \(\approx\)1.8 V, which agrees with the values found in the literature [42; 55]. The initial specific discharge capacities at 0.3 C-rate of LTO with NaCl additions of 0, 2, 4, and 6 wt % were 121.1, 132.4, 145.6, and 113.5 mAh/g, respectively. The LTO-4 wt % NaCl shows the highest initial discharge capacity in this study, which confirms the predictions [50] that the highly crystalline LTO performs at great capacity [17]. However, LTO-6 wt % NaCl has the highest level of crystallinity, but it also has the lowest initial discharge capacity. It means that the addition of 6 wt % NaCl cannot be ignored on LTO material, which is confirmed by the appearance of NaCl peaks in the XRD pattern. In addition, based on the SEM result, the NaCl addition of 6 wt % can cause higher agglomeration on LTO morphology, resulting in the lowest initial specific discharge capacity in this study. It can be concluded that the higher NaCl addition (\(\geq\)6 wt %) causes the NaCl to act as impurities on the LTO material, which will have a poor effect on the electrochemical performance. The initial Coulombic efficiency (CE) of LTO with NaCl additions of 0, 2, 4, and 6 wt % were 84.46%, 90.99%, 91.55%, and 97.84%, respectively. Based on this finding, it can be concluded that a high level of crystallinity results in better structural properties and caused better CE, which is consistent with previous research reported by [PERSON] et al. [18]. In order to investigate the rate ability of LTO without and with NaCl addition, the LTO/LFP battery was charged and discharged at various higher current rates. Figure 4 compares the rate ability of LTO-0 wt % NaCl and LTO-4 wt % NaCl, as tested at 0.3, 1, 3, 5, 7, and 10 C charge-discharge rate. LTO-4 wt % NaCl shows a discharge capacity that ranged from 145.6 mAh/g at 0.3 C to 118.6 mAh/g at 10 C. Meanwhile, LTO-0 wt % NaCl showed a discharge capacity that ranged from 123.8 mA/g at 0.3 C to 86.3 mAh/g at 10 C. It can be seen that the specific capacity of LTO-4 wt % only slightly decreases from 0.3 to 10 C-rate. Compared to LTO-0 wt % NaCl, LTO-4 wt % NaCl has a higher specific capacity at various higher current rates in this study. The capacity retentions of the LTO/LFP battery at 0.3-10 C-rate are presented in Table 2. The LTO-4 wt % NaCl has a smaller drop-specific capacity (18.6%) than LTO-0 wt % NaCl (30.8%) from 0.3 to 10 C-rate.