Volume expansion restriction by TiO₂ structural unit in silicon anodes with yolk–shell structure for lithium-ion batteries

Silicon, due to its high theoretical capacity and abundant resources, has emerged as a potential anode material for lithium-ion batteries (LIBs). However, it suffers from intrinsic capacity decay and rapid degradation, coupled with huge volume expansion that leads to unstable growth of solid electrolyte interface (SEI). Here, we present a straightforward method to construct yolk–shell (YS)-Si/SiO₂-Ti@C materials with YS structure by reducing titanium silicalite-1 (TS-1) with magnesium and altering depositing carbon sequence. Besides, the intermediate space can effectively accommodate the expansion of internal silicon nanoparticles. TiO₂ structural units anchored in the silica alleviate stress–strain in the Si nanoparticles to enhance the cycling stability. The obtained YS-Si/SiO₂-Ti@C composites anode exhibits exceptional reversible capacity and cycling stability compared to YS-Si/SiO₂@C (without TiO₂) and commercial Si electrodes. Notably, the YS-Si/SiO₂-Ti@C composite anode achieves a high specific capacity (1290 mAh·g⁻¹ after 200 cycles at 0.8 A·g⁻¹) and a stable SEI film. Specially, the YS-Si/SiO₂-Ti@C electrode delivers impressive capacity of 1590, 1521, 1222, and 646 mAh·g⁻¹ at 0.8, 2, 4, and 8 A·g⁻¹, respectively. This study paves an avenue for addressing challenge of drastic volume change in silicon during lithiation/delithiation process to improve cycling stability of LIBs.