Polydopamine sacrificial layer mediated SiOx/C@C yolk@shell structure for durable lithium storage

Abstract

SiO_x has aroused great attention as a lithium-ion battery anode material owing to its lower cost and smaller volume expansion than Si. Nevertheless, its practical application is hindered by the still existing volume expansion and low electrical conductivity, resulting in rapid capacity decay. Herein, SiO_x/C@N-doped carbon yolk@shell microspheres (denoted as YS-SiO_x/C@C) have been constructed by a polydopamine-mediated selective etching strategy. In the constructed material, a SiO_x/C composite core is encapsulated in a N-doped hollow carbon sphere with sufficient void space existing between the SiO_x/C core and carbon shell. The yolk@shell structure could buffer the large volume fluctuation, resulting in significantly enhanced structural stability. Benefiting from the structural merits, the new composite delivers a stable high capacity of 804 mA h g⁻¹ at 100 mA g⁻¹ and long-term cyclability (1000 cycles at 500 mA g⁻¹). Besides, the HF-free polydopamine-mediated selective etching strategy developed here paves a new way to construct yolk@shell structures for electrode materials.