Stabilizing lithium deposition within bimodal porous SiO₂-TiO₂ microspheres as 3D host structure

Three-dimensional (3D) host materials for lithium metal anodes (LMAs) have gained attention because they can mitigate volume expansion and local current density through their large surface area and suppress the dendritic growth of lithium. Recent research on 3D host materials has focused on conductive materials; however, the benefits of 3D host materials cannot be fully utilized because lithium deposition begins at the top of the structure. Herein, we fabricate SiO₂-TiO₂ composite microspheres with bimodal pore structures (bi-SiTiO) by simple spray pyrolysis. These microspheres effectively store lithium within the structure from the bottom of the electrode while preventing lithium dendrite formation. Focused ion beam-scanning transmission electron microscopy (FIB-STEM) analysis reveals that the lithiophilic properties of composite microspheres enhanced their effectiveness in storing lithium, with small pores acting as “lithium-ion sieves” for a uniform lithium-ion flux and large pores that provide sufficient volume for lithium deposition. The bi-SiTiO composite microspheres exhibit a high Coulombic efficiency of 98.5% over 200 cycles at 2.0 mA·cm⁻² when operated in a lithium half-cell. With a high lithium loading of 5.0 mAh·cm⁻², the symmetrical cell of the bi-SiTiO electrode sustains more than 900 h. A full cell coupled with an LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode also exhibits enhanced electrochemical properties in terms of cycling stability and rate capability.