Rectifying solid electrolyte interphase structure for stable multi-dimensional silicon anodes

Abstract

Electrolyte engineering is a promising strategy to stabilize electrode structure. However, the high active material utilization of Si anode accompanied by inevitable huge volume expansion makes higher requirements than regulating Li metal deposition behaviors from dendrite growth. Herein, we rectified the solid electrolyte interphase (SEI) layer on Si surface to maintain the electrode integrity during repeated cycling. In our design, an oligomeric buffer layer (CHO₂^-/CH₃O^-) derived from FEC and an inorganic pillar (LiF/Li₃N) derived from LiFSI/LiNO₃ weave into organic-inorganic crosslinking SEI during the initial activation process. Leveraging COMSOL modeling reveals the small stress and strain of the Si particle under the protective effect of concrete SEI layers. Moreover, synchrotron X-ray 3D nano-computed tomography comprehensively elucidates the structural integrity of Si particles during cycling. With this merit, various silicon-based anodes show remarkable cycling stability. Notably, the Si/C || LiFePO₄ full battery still affords a capacity retention ratio exceeding 95% at 1 mA cm⁻² after 300 cycles. This interphase engineering design strategy provided in our work advances the understanding of how to cope with devastating volume variation by leveraging the SEI characteristic perspective.