Silicon anodes usually endure low initial coulombic efficiency (ICE) in applications for lithium‐ion batteries (LIBs), although the volume expansion and structural stability has been greatly improved under many efforts in the recent years. During the first charge and discharge, a large number of lithium ions can participate in the formation of a solid electrolyte interface (SEI) on anode surface, such as LiF, Li₂CO₃ and many Li‐based compounds, resulting in low efficiency, particularly as the nano‐sized silicon is widely applied to solve the volume effect. Herein, we find that the lithium difluorophosphate (LiPO₂F₂, LiDFP) additive shows some special properties, which greatly improve the reversible capacity in the first discharge. The silicon nanoparticles can deliver an ICE of 70.6 % with 2 wt% LiDFP in the electrolyte, which is increased by 17.7 % compared with the cell without LiDFP (ca. 52.9 %). By comparing the XPS and NMR results, it appears the LiDFP may reduce the number of lithium ions involved in the SEI reaction in the electrolyte during the first discharge, and thus the ICE can be improved.

中文翻译：

---

二氟磷酸锂作为提高硅阳极初始库仑效率的有效添加剂

硅阳极通常在锂离子电池（LIB）的应用中具有较低的初始库仑效率（ICE），尽管近年来的许多努力已大大改善了体积膨胀和结构稳定性。在第一次充放电期间，大量锂离子会参与阳极表面上的固体电解质界面（SEI）的形成，例如LiF，Li ₂ CO ₃和许多基于锂的化合物，从而导致效率低下，特别是随着纳米级硅被广泛应用于解决体积效应。在此，我们发现二氟磷酸锂（LiPO ₂ F ₂，LiDFP）添加剂显示出一些特殊的性能，从而大大提高了首次放电时的可逆容量。硅纳米粒子在电解质中含2 wt％的LiDFP时可提供70.6％的ICE，与不带LiDFP的电池（约52.9％）相比，ICE的ICE增加了17.7％。通过比较XPS和NMR结果，似乎LiDFP可以减少第一次放电期间电解质中SEI反应中涉及的锂离子的数量，从而可以改善ICE。