Abstract

The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries. However, the optimal fabrication method for this composite remains a challenge. Here, we developed a novel method using supercritical carbon dioxide (scCO2) to intercalate Si nanoparticles into graphene nanosheets. Silicon was modified with a thin layer of polyaniline, which assisted the dispersion of graphene sheets by introducing π-π interaction. Using scCO2, well-dispersed Si/graphene composite was successfully obtained in a short time under mild temperature. The composite showed high cycle performance (1,789 mAh/g after 250 cycles) and rate capability (1,690 mAh/g at a current density of 4,000 mA/g). This study provides a new approach for cost-effective and scalable preparation of a Si/graphene composite using scCO2 for a highly stable lithium battery anode material.

Highlights

  • The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries

  • Graphene contents were varied for the initial optimization process; based on these results, graphene content was set at 30 wt% for further analyses

  • When a Si nanoparticle was covered by PANi, the color of the particle changed from light to dark brown (Fig. 1b)

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Summary

Introduction

The silicon (Si)/graphene composite has been touted as one of the most promising anode materials for lithium ion batteries. GO has a negative charge resulting from ionization of its carboxylic acid and phenolic hydroxyl groups, which could exert electrostatic attraction with positively charged materials To achieve such attraction, some researchers have tried to modify the surfaces of Si particles with surfactant, polymer, or silane[15,19,20,21]. The prepared Si/reduced graphene oxide composite showed a specific capacity of 1,600 mAh/g after 50 cycles[21] In these studies, Si/graphene composite was obtained using electrostatic interactions; complex pretreatment and post-thermal treatment would be required to modify the Si and to reduce the graphene oxide and/or remove the residual moieties, respectively. Various metal precursors or monomer were used for the reaction under scCO2 fluid; to the best of our knowledge, few studies have tried to prepare Si/graphene composite, which might be due to highly reactive nature of Si precursors

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