A versatile LiTFSI-like anchor for constructing robust interfacial layers with tailored structures for silicon anodes

Abstract

To overcome the severe side reactions induced by the volume changes in silicon (Si) anodes, optimizing and constructing a robust solid electrolyte interphase (SEI) is a prerequisite for the construction of high-energy-density Si-based Li-ion batteries. This work combines the advantages of electrolyte design and surface modification, constructs a phenyl trifluoromethanesulfonimide (PTFSI, with a lithium bis (trifluoromethanesulfonyl) imide-like structure) interfacial layer with electrolyte additive function on the Si surface. The resultant PTFSI-customized interfacial layer modulates the solvation/desolvation reaction mechanism at the electrode interface, constructing an artificial SEI structure composed of oligomers and inorganic salts, which has fast ionic conductivity, and can depress the electrolyte consumption and maintain the integrity of electrode structure. Therefore, the optimized Si@PTFSI anode demonstrates significantly enhanced rate capability and cycling performance. After 300 cycles at 0.5 C, it delivers a capacity of 1241.9 mAh g–1, while the reference Si anode has almost no capacity. Furthermore, LiNi0.5Co0.2Mn0.3O2//Si@PTFSI full-cell delivers a high reversible capacity of 120.1 mAh g–1 at the 300th cycle.