TiO2-Assisted Derivation of Silicon Quantum Dots From Silica Cages Achieving 0.04% Capacity Decay Per Cycle to 900 Cycles.

Ultra-small silicon (Si) quantum dots electrochemically reduced from silica (SiO2) cages enabled the anode to deliver a remarkable initial Coulombic efficiency of near-100%. However, because the practical cycling environment resembles the electrochemical pretreatment conditions, the remaining silica cages continued to be reduced during cycling, leading to capacity fluctuation and gradual decay. In this work, we introduce a TiO2-assisted derivation strategy to regulate the formation of silicon quantum dots from silica cages. The introduction of TiO2 significantly accelerates the electrochemical preprocessing and shortens the activation time, while confining the reduction reaction within the contacted region. Consequently, the mechanical integrity of the robust silica cages can be preserved over prolonged cycling. As a result, the SiO2@TiO2 electrode exhibits excellent cycling stability with only 0.04% capacity decay per cycle up to 900 cycles. Furthermore, the full cell paired with LiFePO4 delivers a high energy density of 362.4 Wh·kg-1 at 1C after 400 cycles, based on the total mass of the cathode and anode active materials.