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

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.

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Thermal diffusivity and conductivity of EG and EG-MNPs-Al.(a) Expanded volume of EG-MNPs-Al after thermal treatment at 700, 800, 900, and 1000 °C, respectively. (b) Thermal diffusivity, and (c) thermal conductivity of the samples listed in Table 1 at different temperatures. (d) The heat conduction schematic diagram of EG-MNPs-Al material along the direction perpendicular to the graphite layers.
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f4: Thermal diffusivity and conductivity of EG and EG-MNPs-Al.(a) Expanded volume of EG-MNPs-Al after thermal treatment at 700, 800, 900, and 1000 °C, respectively. (b) Thermal diffusivity, and (c) thermal conductivity of the samples listed in Table 1 at different temperatures. (d) The heat conduction schematic diagram of EG-MNPs-Al material along the direction perpendicular to the graphite layers.

Mentions: Figure 4a exhibits the influence of expanding temperature on the expanded volume of the EG-MNPs-Al-3 materials. It shows that the expanded volume reaches a maximum value of 265 mL·g−1 at 1000 °C and a higher expanding temperature is beneficial to improve the expanded volume. Figure 4b shows the parallel thermal diffusivity for the samples listed in Table 1. It indicates that the parallel thermal diffusivities monotonically decrease with the temperature increase. Most of the heat transfer mainly occurs by phonons33. As the temperature goes up, the lattice vibration intensifies and the probability of phonon scattering increases, so the parallel thermal diffusivity decreases. However, there was a noticeable difference in heat conducting capability of the EG and EG-MNPs-Al samples. The parallel thermal diffusivity of EG-MNPs-Al is higher than that of EG and reach a maximum value of 1.89 cm2·s−1 at room temperature. The insertion of Al metal nanoparticles into the interlayers of EG can be the possible reason for the higher thermal diffusivity. As shown in Fig. 4c, the corresponding parallel thermal conductivities were also calculated using the formula λ = α • ρ • cp (λ: thermal conductivity, α: thermal diffusivity, ρ: density, cp: specific heat capacity), clearly illustrating the effect of Al adding contents on the parallel thermal conductivity of EG. EG-MNPs-Al materials exhibit a steady improvement in the parallel thermal conductivity compared to the EG materials, and the EG-MNPs-Al-3 attained the highest parallel thermal conductivity value of 11.6 W·m−1·K−1 with a bulk density of 453 kg·m−3 at room temperature, a 150% improvement compared to EG. It is true that the thermal conductivity of Al (~230 W·m−1·K−1) is much higher than graphite in parallel direction (~10 W·m−1·K−1) at room temperature, so that the parallel thermal conductivity improvement of EG-MNPs-Al could be attributed to its special structure with Al metal nanoparticles embedded into the interspaces of EG3435. Figure 4c also shows that the parallel thermal conductivity of EG-MNPs-Al enhances greatly with the weight ratio of added Al increasing. It further indicates that the Al nanoparticles play a key role in the parallel thermal conductivity improvement343637. In addition, the parallel thermal conductivities of all EG-MNPs-Al samples show little variation with temperature, illustrating an outstanding thermal stability of the EG-MNPs-Al samples37.


Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries
Thermal diffusivity and conductivity of EG and EG-MNPs-Al.(a) Expanded volume of EG-MNPs-Al after thermal treatment at 700, 800, 900, and 1000 °C, respectively. (b) Thermal diffusivity, and (c) thermal conductivity of the samples listed in Table 1 at different temperatures. (d) The heat conduction schematic diagram of EG-MNPs-Al material along the direction perpendicular to the graphite layers.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Thermal diffusivity and conductivity of EG and EG-MNPs-Al.(a) Expanded volume of EG-MNPs-Al after thermal treatment at 700, 800, 900, and 1000 °C, respectively. (b) Thermal diffusivity, and (c) thermal conductivity of the samples listed in Table 1 at different temperatures. (d) The heat conduction schematic diagram of EG-MNPs-Al material along the direction perpendicular to the graphite layers.
Mentions: Figure 4a exhibits the influence of expanding temperature on the expanded volume of the EG-MNPs-Al-3 materials. It shows that the expanded volume reaches a maximum value of 265 mL·g−1 at 1000 °C and a higher expanding temperature is beneficial to improve the expanded volume. Figure 4b shows the parallel thermal diffusivity for the samples listed in Table 1. It indicates that the parallel thermal diffusivities monotonically decrease with the temperature increase. Most of the heat transfer mainly occurs by phonons33. As the temperature goes up, the lattice vibration intensifies and the probability of phonon scattering increases, so the parallel thermal diffusivity decreases. However, there was a noticeable difference in heat conducting capability of the EG and EG-MNPs-Al samples. The parallel thermal diffusivity of EG-MNPs-Al is higher than that of EG and reach a maximum value of 1.89 cm2·s−1 at room temperature. The insertion of Al metal nanoparticles into the interlayers of EG can be the possible reason for the higher thermal diffusivity. As shown in Fig. 4c, the corresponding parallel thermal conductivities were also calculated using the formula λ = α • ρ • cp (λ: thermal conductivity, α: thermal diffusivity, ρ: density, cp: specific heat capacity), clearly illustrating the effect of Al adding contents on the parallel thermal conductivity of EG. EG-MNPs-Al materials exhibit a steady improvement in the parallel thermal conductivity compared to the EG materials, and the EG-MNPs-Al-3 attained the highest parallel thermal conductivity value of 11.6 W·m−1·K−1 with a bulk density of 453 kg·m−3 at room temperature, a 150% improvement compared to EG. It is true that the thermal conductivity of Al (~230 W·m−1·K−1) is much higher than graphite in parallel direction (~10 W·m−1·K−1) at room temperature, so that the parallel thermal conductivity improvement of EG-MNPs-Al could be attributed to its special structure with Al metal nanoparticles embedded into the interspaces of EG3435. Figure 4c also shows that the parallel thermal conductivity of EG-MNPs-Al enhances greatly with the weight ratio of added Al increasing. It further indicates that the Al nanoparticles play a key role in the parallel thermal conductivity improvement343637. In addition, the parallel thermal conductivities of all EG-MNPs-Al samples show little variation with temperature, illustrating an outstanding thermal stability of the EG-MNPs-Al samples37.

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.


Related in: MedlinePlus