## 3 Results and Discussions
### The PCM Influence on LIB Temperature under Different Discharging Ratios  
Figure 7 shows the temperature curves of Sanyo and Sony LIB under the conditions of natural convection and PCM cooling. It is found that the PCM has a good effect to decrease the LIB temperature no matter it is discharged at a rate of 1 C or 2 C. Compared with natural convection cooling, the highest temperature of Sanyo LIB decreases about 4.7 \({}^{\circ}\)C and 12.8 \({}^{\circ}\)C for 1 C and 2 C discharging, respectively, and the highest temperature of Sony LIB decreases about 1.1 \({}^{\circ}\)C and 2 \({}^{\circ}\)C. The temperature reduction  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Sanyo** \\ **Saptery** \\ **Cycles** \\ **(mAh)** \\ \end{tabular} } & \multicolumn{2}{c}{**Excon**} & \multicolumn{2}{c}{**Air**} & \multicolumn{2}{c}{**PCM**} & \multicolumn{2}{c}{**PCM-fin**} \\ \cline{2-10}  & **Charging** & **Discharging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** \\  & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** \\  & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** \\  & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** \\ \hline
1 & 2416.836 & 2413.664 & 2397.757 & 2396.380 & 2396.886 & 2385.235 & 2399.645 & 2387.914 \\
2 & 2415.543 & 2412.135 & 2398.268 & 2398.719 & 2401.686 & 2483.068 & 2404.635 & 2379.632 \\
3 & 2414.601 & 2413.030 & 2401.894 & 2400.978 & 2402.126 & 2379.272 & 2405.866 & 2384.824 \\
4 & 2413.782 & 2412.072 & 2395.317 & 2399.563 & 2396.722 & 2382.227 & 2405.228 & 2386.124 \\
5 & 2414.819 & 2413.401 & 2401.893 & 2396.380 & 2395.279 & 2384.336 & 2403.516 & 2378.967 \\
6 & 2412.173 & 2411.815 & 2400.974 & 2397.655 & 2393.280 & 2376.504 & 2402.460 & 2382.489 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Capacity curve of Sanyo LIB in charge and discharge cycles.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **Sany** \\ **Saptery** \\ **Cycles** \\ **(mAh)** \\ \end{tabular} } & \multicolumn{2}{c}{**Excon**} & \multicolumn{2}{c}{**Air**} & \multicolumn{2}{c}{**PCM**} & \multicolumn{2}{c}{**PCM-fin**} \\ \cline{2-10}  & **Charging** & **Discharging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** & **Charging** \\  & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** & **Capacity** \\  & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** & **(mAh)** \\ \hline
1 & 1031.890 & 1032.637 & 1035.779 & 1033.977 & 1032.103 & 1031.853 & 1035.741 & 1024.440 \\
2 & 1008.673 & 1018.444 & 1033.233 & 1035.806 & 1032.359 & 1028.684 & 1031.933 & 1033.147 \\
3 & 1018.732 & 1023.337 & 1034.633 & 1036.101 & 1030.632 & 1029.485 & 1034.568 & 1033.514 \\
4 & 1022.702 & 1026.527 & 1035.109 & 1036.212 & 1031.216 & 1030.508 & 1035.078 & 1033.570 \\
5 & 1025.826 & 1028.784 & 1035.155 & 1036.361 & 1031.566 & 1030.718 & 1034.831 & 1033.665 \\
6 & 1028.002 & 1030.793 & 1035.320 & 1036.645 & 1031.840 & 1031.291 & 1035.110 & 1034.102 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Capacity curve of LiFePO4 LIB in charge and discharge cycles.  
effect of PCM on high rate discharge LIB is more obvious. In the charging and discharging cycles, Sanyo LIB generates more heat due to its large capacity, and PCM absorbs more latent heat. The PCM has the most obvious effect on the Sanyo battery in a 2 C discharging rate among all experiments.