Interfacial Enhancement of Silicon-Based Anode by a Lactam-Type Electrolyte Additive

A silicon-based anode is being developed for industrial application in lithium-ion batteries (LIBs) because of its extremely high theoretical specific capacity. However, the large volume variation during de/lithiation and poor interfacial stability issues cause rapid capacity decay, hindering its practical application. Herein, from the interfacial stabilization point of view, a lactam-based electrolyte additive, namely, N-acetylcaprolactam (donated as NACA), is explored to construct a flexible, robust, and protecting solid electrode interphase (SEI) on the SiOx/C electrode surface. On one hand, due to a stronger complexation with PF5/HF/H2O, NACA functions well in stabilizing the LiPF6 salt, thereby mitigating the corrosion of HF toward the SiOx/C electrode. On the other hand, the NACA-derived interphase could be well adapted to the huge volume change of the silicon electrode. As a consequence, the Li||SiOx/C battery with 2% NACA shows an increase in capacity retention by 15.6% at 30 °C and by 20.8% at 45 °C at 0.5C compared to the baseline. Meanwhile, the cycling performance of the NCM90 cathode is also improved with the NACA additive. Our work provides valuable understanding for seeking more effective amide-based additives for a silicon-based electrode and for the development of functional electrolytes for high-energy-density LIBs.