Ni–Sn intermetallics as an efficient buffering matrix of Si anodes in Li-ion batteries

Abstract

For a successful integration of silicon in high-capacity anodes of Li-ion batteries, its intrinsic capacity decay on cycling due to severe volume swelling should be minimized. In this work, Ni-Sn...

Impact of Surface Chemistry of Silicon Nanoparticles on the Structural and Electrochemical Properties of Si/Ni3.4Sn4 Composite Anode for Li-Ion Batteries

“…For the first galvanostatic cycle of the bare Si R -NiSn composite (Figure 7a), four clear reduction peaks of moderate intensity are observed at 0.66, 0.56, 0.42 and 0.34 V and a broad additional one below 0.1 V. The first four peaks are attributed to lithiation of the main phase (free Sn), whereas the latter one is assigned to the formation of Li-rich Li y Si and Li z Sn alloys [31]. In the anodic branch, four clear oxidation peaks are observed at 0.44, 0.58, 0.70 and 0.78 V, which are attributed to the decomposition of the different Li z Sn alloys (Li 7 Sn 2 , Li 5 Sn 2 , LiSn and Li 2 Sn 5 ) in agreement with previous reports [38,42]. The signal at 0.58 V is in fact a triplet due to the decomposition of three Li z Sn alloys of close composition: Li 13 Sn 5 , Li 5 Sn 2 and Li 7 Sn 3 [42,43].…”

“…This agglomeration favorizes discrete volume changes, leading to electrode cracking [19] and severe capacity decay for the bare Si R -NiSn composite, as observed in Figure 6a. [20,38,44]. The detected dQ/dV peaks for the first galvanostatic cycle in the bare SiR-NiSn composite are consistent with the coexistence of pure Si and Sn phases ( Table 2).…”

“…However, reaction R1 is not fully suppressed on prolonged milling since 2 and 4 wt.% of Sn are detected using XRD for Si C and Si O , respectively. This reveals that carbon coating is more efficient than the oxide one, which is further supported by the fact that the stoichiometry of Ni 3+ x Sn 4 remains constant for the Si C -NiSn composite while it is partially altered for Si O -NiSn ( Table 2 ) [ 38 ]. The lower efficiency of the oxide coating to minimize the reaction between Si and Ni 3.4 Sn 4 can be tentatively attributed to its small thickness (6 nm) and to the fact that the coating also contains Si in the form of SiO 2 .…”

“…The signal at 0.58 V is in fact a triplet due to the decomposition of three Li z Sn alloys of close composition: Li 13 Sn 5 , Li 5 Sn 2 and Li 7 Sn 3 [ 42 , 43 ]. In addition, an anodic bump and a broad oxidation peak can be observed at 0.32 and 0.46 V, which are attributed to the decomposition of amorphous Li 3.16 Si and Li 7 Si 3 alloys, respectively [ 20 , 38 , 44 ]. The detected d Q /d V peaks for the first galvanostatic cycle in the bare Si R -NiSn composite are consistent with the coexistence of pure Si and Sn phases ( Table 2 ).…”

“…To ensure full electrode lithiation, cells were cycled at C/50 for the first cycle, with a voltage window comprised between 0 and 2 V vs. Li + /Li, and at C/20 for the second and third cycles, with a voltage window comprised between 70 mV and 2 V vs. Li + /Li. The cut-off voltage of 70 mV was imposed to avoid the formation of crystalline Li 15 Si 4 phase [ 38 ]. For all subsequent cycles, the kinetic regime was increased to C/10 to accomplish long-term cycling studies (up to 400 cycles) in a reasonable time duration and with a voltage window comprised between 70 mV and 2 V. Reference cycles at a rate of C /20 were done at second and third cycles and after every 20 cycles.…”