## 3 Results and Discussion
### Electrochemical Performance of Negative Plates  
The electrochemical impedance of the negative plates was tested to describe the impact of the additive materials on NAM. The Nyquist plots of impedance consisting of a semicircle and straight-line were analyzed, as shown in Figure 5a. In the plots, the electrolyte impedance of the cells is represented by the intersection point between the  
Figure 4: XPS pattern of the LC composites (**a**) total peak, (**b**) C 1s, (**c**) O 1s and (**d**) Pb-4f. Figure 3: (**a**) SEM image of LC. EDS mapping images of LC. (**b**) C element, (**c**) O element and (**d**) Pb element. semicircle and the real axis, which can also be interpreted as the internal resistance of the batteries [36; 37]. Compared with PLC (0.210 \(\Omega\)) and HPC (0.213 \(\Omega\)), the internal resistance of the LC cell is smaller, i.e., only 0.187 \(\Omega\), which is smaller than that of the control cell. It can be seen that the additive of HPC material works effectively on decreasing the internal resistance of the cells, and the performance of the LC material is better. The diffusion rate of ions in the electrolyte has a direct impact on the quantity of large PbSO\({}_{4}\) particles. Figure 5b illustrates the CV curves of the negative plates with different additives at the scan rate of 5 mV s\({}^{-1}\). It can be seen that, compared with the control electrode, the redox peak current of the negative electrode containing HPC material is significantly increased. It shows that the addition of HPC material can accelerate the oxidation-reduction reaction on the negative electrodes. Table 1 shows the current parameters of oxidation peak (I\({}_{\text{pa}}\)) and reduction peak (I\({}_{\text{pc}}\)). The ratios of the peak current indicate that a part of the chemical reaction in the negative electrodes is irreversible. An important conclusion can be drawn, that is, PbSO\({}_{4}\) crystals on the negative electrodes will inevitably accumulate. Fortunately, the negative electrode with LC has the largest redox current peak ratio. Therefore, the redox process of the cell is the fastest. It also shows that the LC material is able to delay the accumulation of PbSO\({}_{4}\) crystals in the negative electrode. In addition, the largest oxidation peak area in LC cell brings more about lead participating in the chemical reaction, indicating that the LC cell has the largest specific discharge capacity. At the scanning speed of 1 mV s\({}^{-1}\), we rely on the LSV curves to study the hydrogen evolution behavior of the four negative electrodes. Under the same potential conditions, the measured LSV curves are shown in Figure 5c. The slowest hydrogen evolution reaction rate is that of the control electrode, which is followed by the LC electrode, and the fastest rate is that of the HPC electrode. Under the same potential condition of \(-\)1.5 V, the hydrogen evolution currents of the control electrode, LC electrode, PLC electrode, and HPC electrode are \(-\)0.11, \(-\)0.15, \(-\)0.21, and \(-\)0.26 A g\({}^{-1}\), respectively. It can be concluded from the data that the hydrogen evolution reaction of LC is much weaker than that of HPC electrode. This indicated that the inclusion of Pb into HPC helped to slow down the hydrogen evolution reaction. The specific capacity presents another important battery performance indicator, which is directly related to the battery's capacity. Therefore, all cells should be tested for initial specific discharge capacity at 0.1 C. As shown in Figure 6a, compared with the control \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **I\({}_{\text{pa}}\) (A g\({}^{-1}\))** & **I\({}_{\text{pc}}\) (A g\({}^{-1}\))** & **I\({}_{\text{pc}}\)/I\({}_{\text{pa}}\)** \\ \hline LC & 0.87 & 0.64 & 0.73 \\ PLC & 0.65 & 0.43 & 0.66 \\ HPC & 0.64 & 0.39 & 0.60 \\ Control & 0.39 & 0.20 & 0.51 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Redox peak parameters obtained from Figure 5b. Figure 5: (a) Electrochemical impedance spectroscopy, (b) CV curves and (c) LSV curves.