Stabilizing the Solid Electrolyte Interface Using a Zero-Strain Feature Protective Layer for a High-Performance Silicon–Graphite Anode

Abstract

Commercial graphite-based Li-ion batteries almost reached their maximum energy density limits, and the need for high-energy batteries increased tremendously. Silicon (Si) has become a viable anode; however, its enormous volume expansion limits its application. In this regard, the silicon−graphite (Si-G) composite is considered a potential anode to boost the energy density of graphite and alleviate the limitations of silicon. However, the formation of an unstable solid electrolyte interface (SEI) layer impedes its use in practical applications. Hence, constructing a stable SEI layer is crucial to attaining stable and long-term cyclability for Si-G. In this study, we investigated the influence of the Li 4 Ti 5 O 12 (LTO) protective coating on the Si-G composite anode toward the stable SEI layer formation. We found that the LTO coating on Si-G effectively suppresses the parasitic reaction of organic electrolytes with Si and facilitates stable SEI layer formation. In particular, the cross-sectional analysis of the LTO-Si-G electrode using transmission electron microscopy after cycling confirms the presence of stable and thin SEI. In addition, the electrode showed a higher Coulombic efficiency of 99.82%, a high specific capacity of 570.48 mAh g −1 , and enhanced capacity retention of 97.7% after 75 cycles. Our findings highlight that constructing a stable SEI by encasing the Si-G surface with LTO is a promising way to enhance the cycling performance of high-energy Li-ion batteries with the Si-G composite anode.