Reassembled Graphene-Platelets Encapsulated Silicon Nanoparticles for Li-Ion Battery Anodes

Abstract

Among lithium alloy metals, silicon is an attractive candidate to replace commercial graphite anode because silicon possesses about ten times higher theoretical energy density than graphite. However, electrically nonconducting silicon undergoes a large volume changes during lithiation/delithiation reactions, which causes fast loss of storage capacity upon cycling due to electrode pulverization. To alleviate these problems, electrodes comprising Si nanoparticles (20 nm) and graphene platelets, denoted as SiGP-1 (Si = 35.5 wt%) and SiGP-2 (Si = 57.6 wt%), have been prepared with low cost materials and using easily scalable solution-dispersion methods. X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses indicated that Si nanoparticles were highly dispersed and encapsulated between graphene sheets that stacked into platelets in which portions of graphite phases were reconstituted. From the galvanostatic cycling test, SiGP-1 exhibited a reversible lithiation capacity of approximately 802 mAh/g with excellent capacity retention up to 30 cycles at 100 mA/g. Further cycling with a step-increase of current density (100-1,000 mA/g) up to 120 cycles revealed that it has an appreciable power capability as well, showing 520 mAh/g at 1,000 mA/g with capacity loss of 0.2-0.3% per cycle. The improved electrochemical performance is attributed to the robust electrical integrity provided by flexible graphene sheets that encapsulated dispersed Si nanopraticles and stacked into platelets with portions of reconstituted graphite phases in their structure.

A High‐Energy Li‐Ion Battery Using a Silicon‐Based Anode and a Nano‐Structured Layered Composite Cathode

“…In the XRD patterns of Si/C and Si/C‐IWGS shown in Figure S2c, a broad hump at 2 θ = 10–25° is observed corresponding to an amorphous carbon phase with the crystalline Si diffraction peaks at 2 θ = 28.6°, 47.5°, and 56.3° corresponding to the (111), (220), and (311) planes, respectively. In the Si‐graphene composites in which graphene is employed as the sole carbon in relatively high content, the reconstituted graphitic phase is formed where graphene sheets stack and is primarily observed at 2 θ = 26.4° with a relatively high intensity. However, the reconstituted graphitic phase is not observed in the XRD pattern of Si/C‐IWGS partly due to the very low content of graphene (∼6 wt%, see below) in the composite as well as the highly dispersed graphene sheets in the composite without forming thick graphene stacks of a graphitic phase.…”

Rational design of silicon-based composites for high-energy storage devices

“…Graphene, a single-atom-thick layer of sp 2 hybridized carbon in the two-dimensional (2D) form, has been identied as an attractive supporting material that may address the huge volume expansion problems associated with Si anodes. [63][64][65][66][67][68][69][70][71][72] Graphene's many appealing properties such as excellent electrical conductivity, superior mechanical and chemical properties, and extremely high aspect ratio have been successfully exploited in Si/C composites, which are very effective in achieving long cycle life. Lee et al 65 fabricated silicon nanoparticles-graphene paper composites by simple membrane ltering of a homogeneous mixture of SiNPs and graphene oxides (GO) in aqueous solution followed by thermal reduction in a H 2 /Ar gas ow.…”

Dual Carbonaceous Materials Synergetic Protection Silicon as a High-Performance Free-Standing Anode for Lithium-Ion Battery

“…There was an increase in the weight between 650 °C and 800 °C, corresponding to oxidation of Si to SiO 2 under air atmosphere. Thus, the quantity loss for Si/rGO and C@Si/rGO can be calculated from Equations (1) and (2) [56]. X 1 + Y 1 = 1; 1.03X 1 /(1.03X 1 + 0.3340) = 1 − 0.3340 X 2 + Y 2 = 1; 1.03X 2 /(1.03X 1 + 0.3337) = 1 − 0.3337where, X 1 and X 2 are the content of silicon in Si/(C + rGO) and Si/C, respectively.…”