In situ construction of multifunctional Li2Si2O5/LiAlSiO4/C networks on micron silicon anodes for high initial coulombic efficiency

Abstract

The commercialization of silicon anodes is impeded by their initial coulombic efficiency (ICE) and poor cycling stability. Although pre-lithiation has emerged as a promising strategy to address these challenges, existing approaches suffer from high costs, complex processing, and inadequate environmental stability of pre-lithiated products. Herein, we report a scalable solid-state synthesis strategy. Using low-cost fly ash-derived activated carbon as a multifunctional precursor and LiOH as the lithium source, an integrated micro-silicon-based composite was constructed via in situ solid-state reactions during high-temperature treatment. The resulting composite simultaneously incorporates Li₂Si₂O₅ as a pre-lithiation agent, LiAlSiO₄ as a fast ion conductor, and a conductive/buffering carbon network. The composite delivers a high reversible specific capacity of 1564.3 mA h g⁻¹ while substantially improving the ICE of micro-silicon anodes from 77.9% to 93.3%. By optimizing the ratio of lithium source to silicon, the ICE can be further enhanced to 101.1%. Systematic phase evolution analysis and comparative experiments elucidate the synergistic mechanisms of Li₂Si₂O₅-mediated pre-lithiation and LiAlSiO₄-reduced interfacial impedance. This work not only presents a new pathway for high-value utilization of fly ash but also provides novel design principles for pre-lithiation of high-performance micro-silicon-based anodes.