Pre-lithiation strategy enhancing interfacial stability of carbon-coated SiO anodes via controlled formation of LixSiyOz for high-energy lithium-ion batteries

A controllable pre-lithiation strategy is presented, elevating the ICE of carbon-coated SiO from 73.97% to 91.19% and a relatively high-capacity retention rate of 90.98% after 500 cycles at 1.2 A g −1 . • The work unveils the mechanism of interfacial stabilization through multi-scale diagnostics, demonstrating that optimized pre-lithiation fosters a uniform and robust SEI, thereby suppressing continuous electrolyte decomposition. • First-principles calculations confirm the enhanced pre-lithiation kinetics afforded by carbon coating, providing a theoretical foundation for the design of high-performance SiO-based anodes. Low initial coulombic efficiency (ICE) and limited cycling stability obstacle the practical application of silicon monoxide (SiO) as an anode material. To solve these problems, this study proposes to use the Li x Si y O z substance formed during the pre-lithiation process to make up for the coating defects on the surface of carbon-coated SiO to further enhance the interface stability. We studied the pre-lithiation reaction mechanism by adjusting the ratio of lithium to silicon (Li/Si) and combining X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC) and in-situ high-temperature XRD. When the Li/Si ratio is optimized to 12.5%, the ICE of the pre-lithiated composite material significantly increases from 73.97% to 91.19% and a relatively high-capacity retention rate of 90.98% after 500 cycles at 1.2 A g −1 . More importantly, the assembled 2.0 Ah pouch cell has a long-term cycle life of over 700 cycles at 1.0C, with a capacity retention rate of 84.65%. Furthermore, in-situ electrochemical Raman spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) indicate that this pre-lithiation strategy promotes the formation of a more uniform and denser solid electrolyte interface (SEI), thereby suppressing ongoing electrolyte decomposition and reducing continuous electrolyte consumption. First-principles calculations further confirm that the carbon coating enhances the pre-lithiation kinetics of SiO. The controlled pre-lithiation process is schematically illustrated, showing the in-situ formation of an L ix Si y O z buffer layer on carbon-coated SiO, which compensates for coating defects, stabilizes the interface, and leads to significantly enhanced ICE and cycling stability. Download: Download high-res image (190KB) Download: Download full-size image