Tuning Diffusion Preferences in Silicon-Based Anodes for Enhanced Rapid and Homogeneous Lithiation.

Abstract

The inherently sluggish lithiation kinetics of silicon (Si), coupled with its severe volume expansion, causes lithiation retardation and thus exacerbates the failure of Si-based anodes. Here, a Li⁺-diffusion-preference tuning strategy for homogeneous lithiation of Si has been proposed to address these issues and successfully validated through both simulation and experiments using commercial photovoltaic silicon waste (Si_pv). In detail, Li⁺ preferentially diffuses along grain boundaries (GBs) and then into grains, enabling rapid and homogeneous lithiation throughout the Si particles rather than the conventional outside-to-inside lithiation process that suffers from lithiation retardation. Furthermore, the high-concentration GBs impart isotropic lithiation behavior and induce a fine-grain strengthening effect, enhancing the structural stability of Si_pv. The anode prepared by combining Si_pv with graphite (Si_pv/g) thus demonstrates stable cycling with a capacity retention of 93.8% after 1000 cycles. Even at -20 °C, Si_pv/g delivers a 136.2% increase in specific capacity compared to that of commercial Si-based anodes. This work proposes a constructive strategy to essentially improve the electrochemical performance of Si-based anodes.