Polymer configuration conversion mechanism in dynamically stable interface of silicon anodes†

Abstract

Silicon oxide nanospheres (SiOC) have been considered one of the key candidates for the next generation of high-energy-density anode materials. Nevertheless, the intrinsic limitations of their design impede their large-scale commercial deployment, including large volume expansion, poor electrical conductivity, and low initial coulombic efficiency (ICE). The application of a polymer coating represents a beneficial modification. Herein, a composite SiOC anode is synthesized by constructing poly(hexaazatrinaphthalene) (PHATN) on the surface of boron doping-induced self-assembled SiOC nanospheres. The SiOC nanospheres change from a monodisperse structure to a regular and ordered arrangement by self-assembly, which improves the structural stability. A special polymer, PHATN, is selected for its unique structure, which introduces a dynamic conversion mechanism to the material. During the lithium intercalation process, –CN– groups in the PHATN coordinate with Li⁺ to form –C–N–Li– bonds on the PHATN molecule layer. The dynamic volume change of the PHATN molecule allows room for the volume expansion of SiOC, thus providing excellent protection against structural collapse. After 1000 deep cycles, the capacity of the composite anode can be maintained at 623.7 mA h g⁻¹, showing considerable stability and superior specific capacity. PHATN simultaneously repairs the surface defects of the SiOC assemblies and enhances the performance of the SEI membrane, increasing the ICE from 40% to 50%, which exhibits better electrochemical performance.