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Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries

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ABSTRACT

The development of high capacity and long-life lithium-ion batteries is a long-term pursuing and under a close scrutiny. Most of the researches have been focused on exploring electrode materials and structures with high store capability of lithium ions and at the same time with a good electrical conductivity. Thermal conductivity of an electrode material will also have significant impacts on boosting battery capacity and prolonging battery lifetime, which is, however, underestimated. Here, we present the development of an expanded graphite embedded with Al metal nanoparticles (EG-MNPs-Al) synthesized by an oxidation-expansion process. The synthesized EG-MNPs-Al material exhibited a typical hierarchical structure with embedded Al metal nanoparticles into the interspaces of expanded graphite. The parallel thermal conductivity was up to 11.6 W·m−1·K−1 with a bulk density of 453 kg·m−3 at room temperature, a 150% improvement compared to expanded graphite (4.6 W·m−1·K−1) owing to the existence of Al metal nanoparticles. The first reversible capacity of EG-MNPs-Al as anode material for lithium ion battery was 480 mAh·g−1 at a current density of 100 mA·g−1, and retained 84% capacity after 300 cycles. The improved cycling stability and system security of lithium ion batteries is attributed to the excellent thermal conductivity of the EG-MNPs-Al anodes.

No MeSH data available.


TEM images, EDS and XPS of EG-MNPs-Al.(a) TEM image of stacked graphene sheets in EG-MNPs-Al. (b) HRTEM image of EG-MNPs-Al where the lattice planes correspond to (002) planes with an enlarged interlayer distance of 0.387 nm. The right-top inset picture is the corresponding selected area electron diffraction (SAED) pattern. (c) HRTEM image of a section of EG-MNPs-Al embedded with Al metal nanoparticles, (d) corresponding EDS spectrum. (e) XPS spectrum of EG-MNPs-Al.
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f2: TEM images, EDS and XPS of EG-MNPs-Al.(a) TEM image of stacked graphene sheets in EG-MNPs-Al. (b) HRTEM image of EG-MNPs-Al where the lattice planes correspond to (002) planes with an enlarged interlayer distance of 0.387 nm. The right-top inset picture is the corresponding selected area electron diffraction (SAED) pattern. (c) HRTEM image of a section of EG-MNPs-Al embedded with Al metal nanoparticles, (d) corresponding EDS spectrum. (e) XPS spectrum of EG-MNPs-Al.

Mentions: TEM image in Fig. 2a illustrates that the EG-MNPs-Al sample consists of a number of graphene sheets with irregular shapes, and the transparency reveals that the sheets, which resemble a crumpled paper, are composed of a few graphene layers. The disorder-stacking graphene sheets form corrugated and curled structures, and the stacking layers are not commensurate2829. The possible reason is that the expanding process parameters can not be efficiently controlled1626. Therefore, the disordered aggregation leads to the presence of many nanopores and nanocavities in the scrolled graphene sheets, which are favorable to the intercalation of Li+. HRTEM image in Fig. 2b displays that the EG-MNPs-Al possesses the expanded interlayer distances and the long-range channels, which are suitable for lithium ions transport. The average interlayer spacing of (002) plane is measured to be 0.387 nm, which is larger than that of graphite (0.34 nm)30, indicating that the distance between graphite layers is enlarged after the oxidation-expansion process because of the insertion of oxygen-containing groups. The right-top inset picture in Fig. 2b is the selected area electron diffraction (SAED) pattern of the corresponding EG-MNPs-Al. The well-defined diffraction spots fully confirm that the crystal-structure of EG-MNPs-Al is hexagonal. The HRTEM image in Fig. 2c illustrates that Al nanoparticles (indicated as a white circle, the diameter is measured to be about 3 nm) are adhered on the interlayers of the EG sheets. Combined with the EDS spectrum (Fig. 2d), it further corroborates that Al metal nanoparticles existed among the EG sheets, in addition to other elements including O (from oxidation process), S (from H2SO4), Cl (from AlCl3), and Mn (from KMnO4) formed in the preparation process of EG-MNPs-Al.


Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries
TEM images, EDS and XPS of EG-MNPs-Al.(a) TEM image of stacked graphene sheets in EG-MNPs-Al. (b) HRTEM image of EG-MNPs-Al where the lattice planes correspond to (002) planes with an enlarged interlayer distance of 0.387 nm. The right-top inset picture is the corresponding selected area electron diffraction (SAED) pattern. (c) HRTEM image of a section of EG-MNPs-Al embedded with Al metal nanoparticles, (d) corresponding EDS spectrum. (e) XPS spectrum of EG-MNPs-Al.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5037376&req=5

f2: TEM images, EDS and XPS of EG-MNPs-Al.(a) TEM image of stacked graphene sheets in EG-MNPs-Al. (b) HRTEM image of EG-MNPs-Al where the lattice planes correspond to (002) planes with an enlarged interlayer distance of 0.387 nm. The right-top inset picture is the corresponding selected area electron diffraction (SAED) pattern. (c) HRTEM image of a section of EG-MNPs-Al embedded with Al metal nanoparticles, (d) corresponding EDS spectrum. (e) XPS spectrum of EG-MNPs-Al.
Mentions: TEM image in Fig. 2a illustrates that the EG-MNPs-Al sample consists of a number of graphene sheets with irregular shapes, and the transparency reveals that the sheets, which resemble a crumpled paper, are composed of a few graphene layers. The disorder-stacking graphene sheets form corrugated and curled structures, and the stacking layers are not commensurate2829. The possible reason is that the expanding process parameters can not be efficiently controlled1626. Therefore, the disordered aggregation leads to the presence of many nanopores and nanocavities in the scrolled graphene sheets, which are favorable to the intercalation of Li+. HRTEM image in Fig. 2b displays that the EG-MNPs-Al possesses the expanded interlayer distances and the long-range channels, which are suitable for lithium ions transport. The average interlayer spacing of (002) plane is measured to be 0.387 nm, which is larger than that of graphite (0.34 nm)30, indicating that the distance between graphite layers is enlarged after the oxidation-expansion process because of the insertion of oxygen-containing groups. The right-top inset picture in Fig. 2b is the selected area electron diffraction (SAED) pattern of the corresponding EG-MNPs-Al. The well-defined diffraction spots fully confirm that the crystal-structure of EG-MNPs-Al is hexagonal. The HRTEM image in Fig. 2c illustrates that Al nanoparticles (indicated as a white circle, the diameter is measured to be about 3 nm) are adhered on the interlayers of the EG sheets. Combined with the EDS spectrum (Fig. 2d), it further corroborates that Al metal nanoparticles existed among the EG sheets, in addition to other elements including O (from oxidation process), S (from H2SO4), Cl (from AlCl3), and Mn (from KMnO4) formed in the preparation process of EG-MNPs-Al.

View Article: PubMed Central - PubMed

ABSTRACT

The development of high capacity and long-life lithium-ion batteries is a long-term pursuing and under a close scrutiny. Most of the researches have been focused on exploring electrode materials and structures with high store capability of lithium ions and at the same time with a good electrical conductivity. Thermal conductivity of an electrode material will also have significant impacts on boosting battery capacity and prolonging battery lifetime, which is, however, underestimated. Here, we present the development of an expanded graphite embedded with Al metal nanoparticles (EG-MNPs-Al) synthesized by an oxidation-expansion process. The synthesized EG-MNPs-Al material exhibited a typical hierarchical structure with embedded Al metal nanoparticles into the interspaces of expanded graphite. The parallel thermal conductivity was up to 11.6 W·m−1·K−1 with a bulk density of 453 kg·m−3 at room temperature, a 150% improvement compared to expanded graphite (4.6 W·m−1·K−1) owing to the existence of Al metal nanoparticles. The first reversible capacity of EG-MNPs-Al as anode material for lithium ion battery was 480 mAh·g−1 at a current density of 100 mA·g−1, and retained 84% capacity after 300 cycles. The improved cycling stability and system security of lithium ion batteries is attributed to the excellent thermal conductivity of the EG-MNPs-Al anodes.

No MeSH data available.