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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.


The morphology and microstructure of EG-MNPs-Al.(a) SEM image of macroscale EG-MNPs-Al material. (b) SEM image of the expanded orientation of EG-MNPs-Al. (c) SEM image of the interspaces of EG-MNPs-Al sheets. (d) SEM image of worm-shaped EG-MNPs-Al, (e) corresponding Al elemental map and (f) EDS spectrum of the area outlined by the white square in (d).
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f1: The morphology and microstructure of EG-MNPs-Al.(a) SEM image of macroscale EG-MNPs-Al material. (b) SEM image of the expanded orientation of EG-MNPs-Al. (c) SEM image of the interspaces of EG-MNPs-Al sheets. (d) SEM image of worm-shaped EG-MNPs-Al, (e) corresponding Al elemental map and (f) EDS spectrum of the area outlined by the white square in (d).

Mentions: The SEM images and elemental analysis shown in Fig. 1 characterize the morphology and structure of the EG-MNPs-Al material. Figure 1a,b clearly present that the EG-MNPs-Al has a worm-like structure with more than 100 μm large size sheets, and large amounts of slit-shaped pores between the graphite platelets are clearly visible. Figure 1b also shows the presence and orientation of EG sheets in the resulting product, indicating that the natural flake graphite (NFG) expands along c-axis (the direction perpendicular to the graphite layers). Figure 1c exhibits that the EG-MNPs-Al possesses an ideal layer-by-layer structure with an enlarged interlayer spacing and retains an analogous long-range-ordered layered structure2026. It can be attributed to the enormous volume increase during the thermal treatment process. Additionally, at a high temperature, the intercalation agents decompose and force the adjacent graphite layers of graphite intercalation compound (GIC) to separate from each other randomly27. At high magnifications, a kind of honeycomb-like microstructure consisting of many translucent and wrinkled paper-like graphene sheets are observed in Fig. 1c 28. Due to the discontinuous aggregation of curled EG sheets, there are also abundant pores of different sizes (the width of pores is about 3 μm) ranging from macroscale to nanoscale26. Therefore, the interspaces between the EG sheets are easily embedded with small particles and thereby the Al metal nanoparticles could easily insert into the interspaces. The morphology of EG-MNPs-Al shown in Fig. 1d is similar to that of the pure EG, signifying that the Al existing as small nanoparticles is embedded into the interspaces. The Al elemental map (Fig. 1e) and EDS analysis (Fig. 1f) corresponding to the area outlined by the white square in Fig. 1d show a uniform distribution of Al element in the EG-MNPs-Al sample, confirming that the decomposed Al metal nanoparticles are effectively inserted into the framework of the EG host.


Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries
The morphology and microstructure of EG-MNPs-Al.(a) SEM image of macroscale EG-MNPs-Al material. (b) SEM image of the expanded orientation of EG-MNPs-Al. (c) SEM image of the interspaces of EG-MNPs-Al sheets. (d) SEM image of worm-shaped EG-MNPs-Al, (e) corresponding Al elemental map and (f) EDS spectrum of the area outlined by the white square in (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5037376&req=5

f1: The morphology and microstructure of EG-MNPs-Al.(a) SEM image of macroscale EG-MNPs-Al material. (b) SEM image of the expanded orientation of EG-MNPs-Al. (c) SEM image of the interspaces of EG-MNPs-Al sheets. (d) SEM image of worm-shaped EG-MNPs-Al, (e) corresponding Al elemental map and (f) EDS spectrum of the area outlined by the white square in (d).
Mentions: The SEM images and elemental analysis shown in Fig. 1 characterize the morphology and structure of the EG-MNPs-Al material. Figure 1a,b clearly present that the EG-MNPs-Al has a worm-like structure with more than 100 μm large size sheets, and large amounts of slit-shaped pores between the graphite platelets are clearly visible. Figure 1b also shows the presence and orientation of EG sheets in the resulting product, indicating that the natural flake graphite (NFG) expands along c-axis (the direction perpendicular to the graphite layers). Figure 1c exhibits that the EG-MNPs-Al possesses an ideal layer-by-layer structure with an enlarged interlayer spacing and retains an analogous long-range-ordered layered structure2026. It can be attributed to the enormous volume increase during the thermal treatment process. Additionally, at a high temperature, the intercalation agents decompose and force the adjacent graphite layers of graphite intercalation compound (GIC) to separate from each other randomly27. At high magnifications, a kind of honeycomb-like microstructure consisting of many translucent and wrinkled paper-like graphene sheets are observed in Fig. 1c 28. Due to the discontinuous aggregation of curled EG sheets, there are also abundant pores of different sizes (the width of pores is about 3 μm) ranging from macroscale to nanoscale26. Therefore, the interspaces between the EG sheets are easily embedded with small particles and thereby the Al metal nanoparticles could easily insert into the interspaces. The morphology of EG-MNPs-Al shown in Fig. 1d is similar to that of the pure EG, signifying that the Al existing as small nanoparticles is embedded into the interspaces. The Al elemental map (Fig. 1e) and EDS analysis (Fig. 1f) corresponding to the area outlined by the white square in Fig. 1d show a uniform distribution of Al element in the EG-MNPs-Al sample, confirming that the decomposed Al metal nanoparticles are effectively inserted into the framework of the EG host.

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.