Limits...
Silicon carbide-free graphene growth on silicon for lithium-ion battery with high volumetric energy density.

Son IH, Hwan Park J, Kwon S, Park S, Rümmeli MH, Bachmatiuk A, Song HJ, Ku J, Choi JW, Choi JM, Doo SG, Chang H - Nat Commun (2015)

Bottom Line: However, the large volume change of silicon over charge-discharge cycles weakens its competitiveness in the volumetric energy density and cycle life.Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation.The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers.

View Article: PubMed Central - PubMed

Affiliation: Energy Material Lab, Material Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-803, Republic of Korea.

ABSTRACT
Silicon is receiving discernable attention as an active material for next generation lithium-ion battery anodes because of its unparalleled gravimetric capacity. However, the large volume change of silicon over charge-discharge cycles weakens its competitiveness in the volumetric energy density and cycle life. Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation. The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers. When paired with a commercial lithium cobalt oxide cathode, the silicon carbide-free graphene coating allows the full cell to reach volumetric energy densities of 972 and 700 Wh l(-1) at first and 200th cycle, respectively, 1.8 and 1.5 times higher than those of current commercial lithium-ion batteries. This observation suggests that two-dimensional layered structure of graphene and its silicon carbide-free integration with silicon can serve as a prototype in advancing silicon anodes to commercially viable technology.

No MeSH data available.


Related in: MedlinePlus

SiC-free graphene growth on Si NPs.(a) A low-magnification TEM image of Gr–Si NP. (b) A higher-magnification TEM image for the same Gr–Si NP from the white box in a. (Insets) The line profiles from the two red boxes indicate that the interlayer spacing between graphene layers is ∼3.4 Å, in good agreement with that of typical graphene layers based on van der Waals interaction. (c) A high-magnification TEM image visualizing the origins (red arrows) from which individual graphene layers grow. (d) A schematic illustration showing the sliding process of the graphene coating layers that can buffer the volume expansion of Si.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4491181&req=5

f1: SiC-free graphene growth on Si NPs.(a) A low-magnification TEM image of Gr–Si NP. (b) A higher-magnification TEM image for the same Gr–Si NP from the white box in a. (Insets) The line profiles from the two red boxes indicate that the interlayer spacing between graphene layers is ∼3.4 Å, in good agreement with that of typical graphene layers based on van der Waals interaction. (c) A high-magnification TEM image visualizing the origins (red arrows) from which individual graphene layers grow. (d) A schematic illustration showing the sliding process of the graphene coating layers that can buffer the volume expansion of Si.

Mentions: The direct growth of high-quality graphene on Si via CVD process has proven challenging22 because typical graphene synthesis conditions require a reducing atmosphere that tends to strip the native Si oxide layer off the Si surface, and then drives a reaction between Si and decomposed carbon precursors to form SiC23. Our initial approach of using methane (CH4) as a carbon precursor mixed with H2 was indeed unable to achieve a graphene growth on the Si NPs (Supplementary Fig. 1), thereby yielding only β-SiC (Supplementary Fig. 2). To overcome this limitation, we included carbon dioxide (CO2), a mild oxidant, in the CVD process along with CH4 (refs 24, 25). The inclusion of CO2 allows one to avoid the formation of SiC and also lower the growth temperature compared with well-known graphene growth on surface23. In our experiment, at 900 °C, the graphene growth was incomplete or inhomogeneous (Supplementary Fig. 3), whereas graphene growth at 1,100 °C produced oxide layers on the Si surface that are too thick for efficient Li ion diffusion (Supplementary Fig. 4). At an intermediate temperature of 1,000 °C, 2–10 layers of graphene were formed as shown in transmission electron microscope (TEM) images (Fig. 1a,b) clearly displaying the layered structure as well as the interlayer distance near 3.4 Å (Fig. 1b, inset). Closer inspection indicates that individual layers are anchored directly to the Si particle surface at their ends (red arrows in Fig. 1c) and lie parallel to the Si surface. These well-aligned graphene layers can maintain their layered stacking structure even during lithiation via a sliding process (Fig. 1d), thus providing an elegant means to accommodate the volume expansion of Si. Graphene growth has been attempted on Si dioxide (SiO2) surfaces using CH4 and H2 (refs 26, 27). However, the graphene growth in those processes was very inefficient or does not avoid SiC formation. The inefficient growth is ascribed to insufficient catalytic sites on SiO2 surface. By contrast, in our process, the CO2 addition generates more catalytic sites in the form of SiOx with some defects.


Silicon carbide-free graphene growth on silicon for lithium-ion battery with high volumetric energy density.

Son IH, Hwan Park J, Kwon S, Park S, Rümmeli MH, Bachmatiuk A, Song HJ, Ku J, Choi JW, Choi JM, Doo SG, Chang H - Nat Commun (2015)

SiC-free graphene growth on Si NPs.(a) A low-magnification TEM image of Gr–Si NP. (b) A higher-magnification TEM image for the same Gr–Si NP from the white box in a. (Insets) The line profiles from the two red boxes indicate that the interlayer spacing between graphene layers is ∼3.4 Å, in good agreement with that of typical graphene layers based on van der Waals interaction. (c) A high-magnification TEM image visualizing the origins (red arrows) from which individual graphene layers grow. (d) A schematic illustration showing the sliding process of the graphene coating layers that can buffer the volume expansion of Si.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491181&req=5

f1: SiC-free graphene growth on Si NPs.(a) A low-magnification TEM image of Gr–Si NP. (b) A higher-magnification TEM image for the same Gr–Si NP from the white box in a. (Insets) The line profiles from the two red boxes indicate that the interlayer spacing between graphene layers is ∼3.4 Å, in good agreement with that of typical graphene layers based on van der Waals interaction. (c) A high-magnification TEM image visualizing the origins (red arrows) from which individual graphene layers grow. (d) A schematic illustration showing the sliding process of the graphene coating layers that can buffer the volume expansion of Si.
Mentions: The direct growth of high-quality graphene on Si via CVD process has proven challenging22 because typical graphene synthesis conditions require a reducing atmosphere that tends to strip the native Si oxide layer off the Si surface, and then drives a reaction between Si and decomposed carbon precursors to form SiC23. Our initial approach of using methane (CH4) as a carbon precursor mixed with H2 was indeed unable to achieve a graphene growth on the Si NPs (Supplementary Fig. 1), thereby yielding only β-SiC (Supplementary Fig. 2). To overcome this limitation, we included carbon dioxide (CO2), a mild oxidant, in the CVD process along with CH4 (refs 24, 25). The inclusion of CO2 allows one to avoid the formation of SiC and also lower the growth temperature compared with well-known graphene growth on surface23. In our experiment, at 900 °C, the graphene growth was incomplete or inhomogeneous (Supplementary Fig. 3), whereas graphene growth at 1,100 °C produced oxide layers on the Si surface that are too thick for efficient Li ion diffusion (Supplementary Fig. 4). At an intermediate temperature of 1,000 °C, 2–10 layers of graphene were formed as shown in transmission electron microscope (TEM) images (Fig. 1a,b) clearly displaying the layered structure as well as the interlayer distance near 3.4 Å (Fig. 1b, inset). Closer inspection indicates that individual layers are anchored directly to the Si particle surface at their ends (red arrows in Fig. 1c) and lie parallel to the Si surface. These well-aligned graphene layers can maintain their layered stacking structure even during lithiation via a sliding process (Fig. 1d), thus providing an elegant means to accommodate the volume expansion of Si. Graphene growth has been attempted on Si dioxide (SiO2) surfaces using CH4 and H2 (refs 26, 27). However, the graphene growth in those processes was very inefficient or does not avoid SiC formation. The inefficient growth is ascribed to insufficient catalytic sites on SiO2 surface. By contrast, in our process, the CO2 addition generates more catalytic sites in the form of SiOx with some defects.

Bottom Line: However, the large volume change of silicon over charge-discharge cycles weakens its competitiveness in the volumetric energy density and cycle life.Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation.The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers.

View Article: PubMed Central - PubMed

Affiliation: Energy Material Lab, Material Research Center, Samsung Advanced Institute of Technology, Samsung Electronics Co., Ltd, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 443-803, Republic of Korea.

ABSTRACT
Silicon is receiving discernable attention as an active material for next generation lithium-ion battery anodes because of its unparalleled gravimetric capacity. However, the large volume change of silicon over charge-discharge cycles weakens its competitiveness in the volumetric energy density and cycle life. Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation. The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers. When paired with a commercial lithium cobalt oxide cathode, the silicon carbide-free graphene coating allows the full cell to reach volumetric energy densities of 972 and 700 Wh l(-1) at first and 200th cycle, respectively, 1.8 and 1.5 times higher than those of current commercial lithium-ion batteries. This observation suggests that two-dimensional layered structure of graphene and its silicon carbide-free integration with silicon can serve as a prototype in advancing silicon anodes to commercially viable technology.

No MeSH data available.


Related in: MedlinePlus