Boosting Superior Lithium Storage Performance of Alloy-Based Anode Materials via Ultraconformal Sb Coating-Derived Favorable Solid-Electrolyte Interphase

Alloy materials such as Si and Ge are attractive as high-capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge-charge processes. Compared to the over-emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid-electrolyte interphase (SEI) are significantly lacking. This work demonstrates that modifying the surface of alloy-based anode materials by building an ultraconformal layer of Sb can significantly enhance their structural and interfacial stability during cycling. Combined experimental and theoretical studies consistently reveal that the ultraconformal Sb layer is dynamically converted to Li3Sb during cycling, which can selectively adsorb and catalytically decompose electrolyte additives to form a robust, thin, and dense LiF-dominated SEI, and simultaneously restrain the decomposition of electrolyte solvents. Hence, the Sb-coated porous Ge electrode delivers much higher initial Coulombic efficiency of 85% and higher reversible capacity of 1046 mAh g(-1) after 200 cycles at 500 mA g(-1), compared to only 72% and 170 mAh g(-1) for bare porous Ge. The present finding has indicated that tailoring surface structures of electrode materials is an appealing approach to construct a robust SEI and achieve long-term cycling stability for alloy-based anode materials.