Yolk-Shell Gradient-Structured SiO_x Anodes Derived from Periodic Mesoporous Organosilicas Enable High-Performance Lithium-Ion Batteries

Gradient-structured materials hold great promise in the areas of batteries and electrocatalysis. Here, yolk-shell gradient-structured SiO_x -based anode (YSG-SiO_x /C@C) derived from periodic mesoporous organosilica spheres (PMOs) through a selective etching method is reported. Capitalizing on the poor hydrothermal stability of inorganic silica in organic-inorganic hybrid silica spheres, the inorganic silica component in the hybrid spheres is selectively etched to obtain yolk-shell-structured PMOs. Subsequently, the yolk-shell PMOs are coated with carbon to fabricate YSG-SiO_x /C@C. YSG-SiO_x /C@C is comprised of a core with uniform distribution of SiO_x and carbon at the atomic scale, a middle void layer, and outer layers of SiO_x and amorphous carbon. This unique gradient structure and composition from inside to outside not only enhances the electrical conductivity of the SiO_x anode and reduces the side reactions, but also reserves void space for the expansion of SiO_x , thereby effectively mitigating the stress caused by volumetric effect. As a result, YSG-SiO_x /C@C exhibits exceptional cycling stability and rate capability. Specifically, YSG-SiO_x /C@C maintains a specific capacity of 627 mAh g^-1 after 400 cycles at 0.5 A g^-1 , and remains stable even after 550 cycles at current density of 2 A g^-1 , achieving a specific capacity of 519 mAh g^-1 .