Controllable Synthesis and Lithium Storage Performance of Graphene Network@Mesoporous Carbon Integrated with Nano Silicon and Metal Oxides

Description

Silicon (Si) and metal oxides are promising candidates for the next-generation Li-ionbattery anode materials as substitute for existing commercial graphite anodes because oftheir high theoretical specific capacities, abundance, easy preparation, and low cost.These candidates have many advantages, but their poor electrical conductivity and slowLi-ions diffusion in solid bulk materials greatly limit the rate capabilities for fastcharge/discharge. In addition, the dramatic volume change in these elements duringcharge/discharge results in pulverization and exfoliation from the current collector,leading to poor cycling performance and rapid capacity decay. Thus, the practicalapplications of Si and metal oxides are greatly challenged until today given their poorrate and cycling capability.This project aims to synthesize a versatile 3D hierarchical graphenenetworks@mesoporous carbon (3D-HGN@MPC) core-shell nanostructure andincorporate it with Si and metal oxides to obtain high-performance anode materials.This project is the first synthesis of a hierarchical carbon structure with a 3D graphenenetwork core and a mesoporous carbon shell, whose thickness and pore size are tunable.The synthesis is based on a layer-by-layer assembly and a soft template method formesoporous carbon through template removal, graphene oxide reduction, heat-inducedassembly, and polymer carbonization. 3D-HGN@MPC is first integrated with nano Si(and metal oxides), and the hierarchical 3D graphene layer then fills the void spacebetween the Si (and metal oxides) core and the outer carbon shell. Filling the void spacecan further improve electronic conductivity compared with the electrodes with a commonyolk-shell structure. In addition, this unique 3D-HGN@MPC carbon material with 3Dhierarchical interconnected pores facilitates the infiltration of electrolyte to ensure theefficient interfacial contact among electrolyte ions, electroactive materials, andmesoporous carbon shell. These features lead to excellent rate performance of theelectrode and provide great potential for fast charge and discharge in practicalapplications. The dual protection provided by the 3D graphene layer and the mesoporouscarbon shell can effectively buffer and restrict the volume change of the electroactivematerials and thus increase cycle stability. This project will deliver important theoreticaland experimental bases for designing exceptional anode materials with high capacity,high rate, and long cycle life.