SiOx enhances prelithiation kinetics and homogeneity in graphite-based anodes

Abstract

Graphite anodes deliver outstanding cycling stability but are limited to a theoretical capacity of 372 mA h g⁻¹. Blending silicon oxide (SiO_x) (1600 mA h g⁻¹) with graphite can boost energy density while partially overcoming the drawbacks of each component, yet the composite suffers from the intrinsically low initial coulombic efficiency of SiO_x. Prelithiation, adding lithium to the anode before full-cell assembly, is an effective route to recover this first-cycle Li loss and raise ICE, but practical implementation is non-trivial. Ultrathin Li foils (sub 3 μm) would be ideal prelithiation sources, although producing and handling such fragile foils at scale remain difficult. Moreover, prelithiation kinetics differ markedly between the two active phases: graphite lithiates slowly, leading to non-uniform Li uptake and local over-lithiation, whereas SiO_x accepts Li rapidly and homogeneously. This study replaces continuous foils with an array of lithium strips, eliminating the stringent thickness requirement, enables quantitative control of the lithium dose via strip pitch and width, and preserves open gaps that facilitate electrolyte penetration and ion transport. Lithium from the strips is initially absorbed by the SiO_x domains; the subsequent diffusion of Li⁺ into graphite creates a uniform lithium gradient across the electrode and suppresses local over-lithiation. The resulting prelithiated SiO_x/graphite anode achieves a 96% ICE and retains 82% of its capacity after 1100 cycles in LiFePO₄ full cells without observable structural degradation. The Li-strip array prelithiation strategy, combined with rational SiO_x distribution, offers a scalable pathway toward high-energy-density, long-life lithium-ion batteries.