context: To overcome this limitation, analysis of Differential Capacity Plots (DCPs) has been performed to identify electrochemical charge/discharge reactions and track their evolution during cycling. Fig. 6 shows the DCPs for the different Si/Ni–Sn/Al/C composites at cycles 2, 80 and 200 corresponding to composite activation, maximum capacity and end-of-cycling states. For Si-B, at the 2nd lithiation (Fig. 6a), three reduction peaks are observed in the cathodic branch. The peak at 0.17 V is attributed to the reaction potential of amorphous Si with lithium to form LixSi alloys of approximate composition LiSi and Li7Si3. Silicon amorphisation is known to occur during the first lithiation of crystalline Si anodes. The two other reduction peaks at 0.31 and 0.62 V are attributed to the formation of LiySn alloys: Li7Sn2 and LiSn, respectively. On delithiation, multiple oxidation peaks are detected and are attributed to the decomposition of Li7Si3 at 0.51 V and different LiySn alloys: Li7Sn2 (or Li22Sn5), Li5Sn2, LiSn and Li2Sn5 at 0.47, 0.58, 0.74 and 0.81 V, respectively. The two phases Li7Sn3 and Li13Sn5 have compositions close to Li5Sn2 and could be involved in the delithiation process at 0.58 V. For both composites Si-AB and Si-A, poorly defined cathodic peaks are found at the 2nd lithiation, but DCPs exhibit significant features in delithiation. For Si-AB, two oxidation peaks are clearly identified at 0.47 and 0.58 V attributed to the decomposition of Li7Sn2 (or Li22Sn5) and Li5Sn2 alloys, respectively. For Si-A, a unique broad oxidation peak is observed at 0.51 V assigned to the decomposition of Li7Si3. Interestingly, no signal related to the decomposition of LiySn alloys is detected for the composite Si-A, suggesting that Ni3Sn2 does not react with lithium.
answer: Si 