It is challenging to design silicon anode exhibiting stable cycling behavior, high volumetric and specific capacity, and low volume expansion for Li-based batteries.Herein, we designed Si/C-IWGN composites (Si/C composites internally-wired with graphene networks). For this purpose, we used simple aqueous sol-gel systems consisting of varying amounts of silicon nanoparticles, resorcinol-formaldehyde, and graphene oxide. We found that that a small amount of graphene (1-10 wt%) in Si/C-IWGNs efficiently stabilized its cycling behavior. The enhanced cycling stability of Si/C-IWGNs could be ascribed to the following facts: 1) ideally dispersed graphene networks were formed in the composites, 2) these graphene networks also created enough void spaces for silicon to expand and contract with the electrode thickness increase comparable to that of graphite. Furthermore, properly designed Si/C-IWGNs exhibited high volumetric capacity of ~141% greater than that of commercial graphite.Finally, a hybrid sample, Si-Gr, consisting of a high capacity Si/C-IWGN and graphite was prepared to demonstrate a hybrid strategy for a reliable and cost-effective anode with a capacity level required in high-energy Li-ion cells. The Si-Gr hybrid exhibited not only high capacity (800-900 mAh g -1 at 100 mA g -1 ) but also high electrode volumetric capacity of 161% greater than that of graphite. 6 large fraction of void spaces between nanoparticles and graphene networks in these composites. Since, Si/C composites are internally-wired with graphene networks, they are denoted as Si/C-IWGNs hereafter. The Si/C-IWGN samples were simply prepared by carbonizing the composite gels formed in aqueous mixtures consisting of SiNPs, resorcinol(R)-formaldehyde (F) as the carbon precursor and a small amount of graphene oxide (GO) in one-pot reactions as shown in Scheme 1. Various Si/C-IWGN samples were prepared with different contents of SiNPs (40 or 50 wt%) and graphene (1, 5 and 10 wt%). Two types of gelation catalysts (C), Na 2 CO 3 or NH 4 OH, with different concentration (R/C ratio = 100-500 in molar) were used for forming composite gels.Various electrochemical responses of Si/C-IWGNs, such as cycling stability, volumetric as well as specific capacity, Coulombic efficiency, and electrode thickness increase, are thoroughly compared with those of the following reference samples: 1) control composites, Si/C composites, which were prepared without GO addition in the gel formation process in Scheme 1, and 2) commercial graphite. Finally, we have demonstrated a hybrid strategy to develop a reliable and low-cost anode materials consisting of mixtures of high capacity Si/C-IWGNs and commercial graphite.
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