Limits...
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.

No MeSH data available.


Insertion/extraction mechanisms.Schematic diagrams of the insertion/extraction mechanisms of Li+ in (a) NFG, (b) EG and (c) EG-MNPs-Al.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5037376&req=5

f6: Insertion/extraction mechanisms.Schematic diagrams of the insertion/extraction mechanisms of Li+ in (a) NFG, (b) EG and (c) EG-MNPs-Al.

Mentions: In order to further understand the high reversible capacity and good cyclic stability of the EG-MNPs-Al material, the possible intercalation mechanisms of Li+ in NFG, EG and EG-MNPs-Al are schematically depicted in Fig. 6. The interpretive schematic shows that the Li+ insertion/extraction mechanisms of NFG, EG and EG-MNPs-Al are different from each other. According to the references1643, Li ions tend to be electrochemically absorbed on both sides of single-layer sheets that are arranged horizontally. The Li+ intercalated sites in graphite are predominantly interlayer space between the adjacent graphite layers due to the lamellar structure (Fig. 6a). However, the EG-MNPs-Al possesses a layer-by-layer structure with an enlarged interlayer lattice distance. It is more favorable to the electrochemical absorption of Li+ between the graphite layers, and can offer more Li+ insertion active sites44. Furthermore, the curled structure and disorder stacking of graphene sheets provide large amounts of pores or defects, resulting in a geometrical increase of Li+ intercalation numbers. Due to the enlarged interlayer space and the existence of graphene sheets, the unique structure of EG-MNPs-Al has many channels that can provide more effective Li+ insertion sites so that the diffusion of Li+ takes place easily. Thus, it effectively facilitates Li+ to reversibly insert into and extract from the electrode materials and thereby limits the formation of dead lithium. This reversible insertion/extraction is responsible for the excellent cycling stability of the electrode materials. Most importantly, the EG-MNPs-Al material possesses a particular hierarchical structure with metal particles embedded into the interspaces of EG, so that the alloying reaction between Al and Li may take place during the cycling (Fig. 6c). Owing to the formation of LixAl alloy, the Li+ storage capability of EG-MNPs-Al can be enhanced, higher than that of EG (Fig. 6b). And this is also the most important reason why the EG-MNPs-Al material delivers a higher reversible capacity than the other EG reported by previous studies171819. Therefore, the particular structure of the EG-MNPs-Al electrode material plays an important role in enhancing the large reversible capacity and cycling stability.


Expanded graphite embedded with aluminum nanoparticles as superior thermal conductivity anodes for high-performance lithium-ion batteries
Insertion/extraction mechanisms.Schematic diagrams of the insertion/extraction mechanisms of Li+ in (a) NFG, (b) EG and (c) EG-MNPs-Al.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f6: Insertion/extraction mechanisms.Schematic diagrams of the insertion/extraction mechanisms of Li+ in (a) NFG, (b) EG and (c) EG-MNPs-Al.
Mentions: In order to further understand the high reversible capacity and good cyclic stability of the EG-MNPs-Al material, the possible intercalation mechanisms of Li+ in NFG, EG and EG-MNPs-Al are schematically depicted in Fig. 6. The interpretive schematic shows that the Li+ insertion/extraction mechanisms of NFG, EG and EG-MNPs-Al are different from each other. According to the references1643, Li ions tend to be electrochemically absorbed on both sides of single-layer sheets that are arranged horizontally. The Li+ intercalated sites in graphite are predominantly interlayer space between the adjacent graphite layers due to the lamellar structure (Fig. 6a). However, the EG-MNPs-Al possesses a layer-by-layer structure with an enlarged interlayer lattice distance. It is more favorable to the electrochemical absorption of Li+ between the graphite layers, and can offer more Li+ insertion active sites44. Furthermore, the curled structure and disorder stacking of graphene sheets provide large amounts of pores or defects, resulting in a geometrical increase of Li+ intercalation numbers. Due to the enlarged interlayer space and the existence of graphene sheets, the unique structure of EG-MNPs-Al has many channels that can provide more effective Li+ insertion sites so that the diffusion of Li+ takes place easily. Thus, it effectively facilitates Li+ to reversibly insert into and extract from the electrode materials and thereby limits the formation of dead lithium. This reversible insertion/extraction is responsible for the excellent cycling stability of the electrode materials. Most importantly, the EG-MNPs-Al material possesses a particular hierarchical structure with metal particles embedded into the interspaces of EG, so that the alloying reaction between Al and Li may take place during the cycling (Fig. 6c). Owing to the formation of LixAl alloy, the Li+ storage capability of EG-MNPs-Al can be enhanced, higher than that of EG (Fig. 6b). And this is also the most important reason why the EG-MNPs-Al material delivers a higher reversible capacity than the other EG reported by previous studies171819. Therefore, the particular structure of the EG-MNPs-Al electrode material plays an important role in enhancing the large reversible capacity and cycling stability.

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.