3D Si/C particulate nanocomposites internally wired with graphene networks for high energy and stable batteries

Abstract

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. Experimental

Critical Insight into the Relentless Progression Toward Graphene and Graphene‐Containing Materials for Lithium‐Ion Battery Anodes

“…K. Lee et al, [ 374 ] synthesizing Si/RGO composites with a variable content of graphene (in the 1-10 wt% range), showed how the graphene matrix effectively stabilizes the electrode upon cycling. Moreover, using strategic material design, one of the composites exhibited a high volumetric capacity of about 141% higher than commercial graphite, even if the material's density was only 0.55 g cm −3 .…”

High-Performance Li-Ion Battery Anodes Based on Silicon-Graphene Self-Assemblies

“…However, the electrochemical reaction between nonconducting silicon and lithium ions is accompanied by a huge net volume expansion (∼300%) 15,17,18 followed by electrode pulverization, leading to rapid capacity fading due to loss of electrical contact, growth of a newly formed unstable solid-electrolyte interface (SEI), 19,20 electrolyte depletion, and so on. To address these issues associated with silicon, tremendous research efforts have been devoted z E-mail: jklee88@dau.ac.kr to rational designs of silicon-based composites in which the huge volume variation is effectively accommodated and thus the electrical network is well preserved to secure a long cycle life.Among many conducting carbonaceous platforms for the formation of silicon-based composites, graphene has been effectively incorporated in a variety of formats to enhance the cycling stability of silicon:11, 21-38 a self-supporting silicon nanoparticle (SiNP)-graphene paper composite prepared by simple membrane filtering of a homogeneous aqueous mixture of SiNPs or silicon nanowires and graphene oxide (GO), 21,22,28,32 crumpled-graphene-encapsulated SiNPs prepared by an aerosol-assisted capillary assembly method, 24 graphene granules or a graphene hybrid coated with nanosilicon by chemical vapor deposition, 23,30 Si/C composites internally wired with dispersed graphene networks prepared by a solution-based sol-gel process, 11,39 Si-graphene composites prepared by an electrostatic self-assembly method, 25,27,29,31,40 and conformal growth of graphene cages on the surface of silicon particles by a Ni-catalyzed dissolutionprecipitation mechanism. …”

“…11, 21-38 a self-supporting silicon nanoparticle (SiNP)-graphene paper composite prepared by simple membrane filtering of a homogeneous aqueous mixture of SiNPs or silicon nanowires and graphene oxide (GO), 21,22,28,32 crumpled-graphene-encapsulated SiNPs prepared by an aerosol-assisted capillary assembly method, 24 graphene granules or a graphene hybrid coated with nanosilicon by chemical vapor deposition, 23,30 Si/C composites internally wired with dispersed graphene networks prepared by a solution-based sol-gel process, 11,39 Si-graphene composites prepared by an electrostatic self-assembly method, 25,27,29,31,40 and conformal growth of graphene cages on the surface of silicon particles by a Ni-catalyzed dissolutionprecipitation mechanism.…”

Engineering Carbon Distribution in Silicon‐Based Anodes at Multiple Scales

“…[15] Methane gas alwayss erves as the carbon source to produce graphene when using the CVD reac-tor. [18] Compositingw ith 2D graphene can remarkably improve the initial coulombic efficiencyo wing to the lower number of surface dangling bonds. [17] For the preparation of GO, graphite is the most frequentlya dopted carbons ource based on the famous Hummer's method.…”