Enabling robust structural and interfacial stability of micron-Si anode toward high-performance liquid and solid-state lithium-ion batteries

Silicon (Si) anode holds great promise for next-generation high-energy-density lithium-ion batteries (LIBs) due to its ultrahigh theoretical capacity and earth-abundant nature. However, its poor structural and interfacial stability caused by severe volume change and continuous side reactions with highly permeable liquid electrolytes lead to substantial capacity fading with cycling, which impedes its practical application. Here, a novel SiO2@Li3PO4@carbon shell coated on micron-sized Si (MSi) (denoted as Si@SiO2@LPO@C) is designed for the first time, which has been shown to release the stress and maintain the mechanical integrity while ensuring stable solidelectrolyte interphase (SEI). Moreover, the in-situ formed SiO2 interlayer can reduce the energy barrier of Li+ transport from Li3PO4 shell to Si core, as confirmed by theoretical simulations. Notably, the SEI originated from PEO/LITFSI solid-state electrolyte not only comprises more ratio of stable LiF but also only grows on outer surface of MSi, as evidenced by Cryo-transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) measurements. Consequently, the as-fabricated Si@SiO2@LPO@C anode demonstrates stable cycling performance with high capacities in LIBs with both liquid and solid-state electrolytes. Particularly, the Si@SiO2@LPO@C anode enables stable cycling stability, maintaining a specific capacity of 1012.4 mAh g-1 over 200 cycles and 1441.0 mAh g- 1 after 80 cycles in half and full solid-state LIBs, respectively. Our unique design that enables robust mechanical structure, favorable Li+ pathway, and stable interfacial chemistry of MSi anode with high capacity and stable cycle performance, is expected to extend to other alloy electrodes for high-energy liquid and solid-state batteries.