Tailoring Multilayer Fine-Grained Solid Electrolyte Interphase by Pulse Electrochemical Activation Maneuver for Stable Si/C Anodes

Abstract

Silicon (Si) is widely regarded as one of the most promising anode materials for lithium-ion batteries due to its exceptionally high specific capacity. However, the significant volumetric changes (up to 400%) of Si anode degrades the solid-electrolyte interphase (SEI) and significantly hinders its practical application. Herein, we modulate the formation of fine-grained SEI composed of multiple layers by pulse electrochemical activation mode, where each layer is uniformly distributed with fine inorganic particles and interspersed with buffer organics. This tailored multilayer fine-grained SEI effectively promotes the lithium-ion diffusion kinetics through SEI featuring a small Gibbs free energy (0.235 eV), which is only 1/5 of the typical double-layer SEI, as well as smaller charge transfer resistances during the whole electrochemical processes. Moreover, it exhibits a high Young’s modulus of 12.5 GPa in comparison to that of the typical double-layer SEI (5.1 GPa) and much-inhibited stress and strain, so as to generate lower thickness expansion/shrinkage ratios. Consequently, the assembled Si/C || LiFePO4 full cell, operating at a current density of 1 A g−1, demonstrates a remarkable capacity retention of 93.6% after 583 cycles, which also shows a practical application by powering an unmanned aircraft. This interfacial engineering maneuver sheds light on enhancing the electrochemical performance of other high-capacity electrode materials with substantial volume changes.