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Improving battery safety by reducing the formation of Li dendrites with the use of amorphous silicon polymer anodes.

Maruyama H, Nakano H, Ogawa M, Nakamoto M, Ohta T, Sekiguchi A - Sci Rep (2015)

Bottom Line: The currently used anode materials have low redox voltages that are very close to the redox potential for the formation of Li metal, which leads to severe short circuiting.Equally as significant, poly(methylsilyne) and poly(phenylsilyne) are capable of reacting with 0.45 and 0.9 Li atoms per formula unit, respectively, at an average voltage of approximately 1.0 V, affording reversible capacities of 244 mAh·g(-1) and 180 mAh·g(-1).Moreover, noteworthy is the fact that polysilynes are suitable for practical applications because they can be prepared through a simple and low-cost process and are easy to handle.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.

ABSTRACT
To provide safe lithium-ion batteries (LIBs) at low cost, battery materials which lead to reduced Li dendrite formation are needed. The currently used anode materials have low redox voltages that are very close to the redox potential for the formation of Li metal, which leads to severe short circuiting. Herein, we report that when the three-dimensional amorphous silicon polymers poly(methylsilyne) and poly(phenylsilyne) are used as anode materials, dendritic Li formation on the anode surface is avoided up to a practical current density of 10 mA·g(-1) at 5 °C. Equally as significant, poly(methylsilyne) and poly(phenylsilyne) are capable of reacting with 0.45 and 0.9 Li atoms per formula unit, respectively, at an average voltage of approximately 1.0 V, affording reversible capacities of 244 mAh·g(-1) and 180 mAh·g(-1). Moreover, noteworthy is the fact that polysilynes are suitable for practical applications because they can be prepared through a simple and low-cost process and are easy to handle.

No MeSH data available.


Related in: MedlinePlus

SEM images of different anodes before and after Li insertion.Initial surface of anodes based on (a) graphite and (d) poly(methylsilyne) 1. SEM images of (b,c) graphite and (e,f) poly(methylsilyne) 1 after Li insertion at 10 mA·g−1 and 100 mA·g−1, respectively.
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f5: SEM images of different anodes before and after Li insertion.Initial surface of anodes based on (a) graphite and (d) poly(methylsilyne) 1. SEM images of (b,c) graphite and (e,f) poly(methylsilyne) 1 after Li insertion at 10 mA·g−1 and 100 mA·g−1, respectively.

Mentions: Finally, to assess the low-temperature performances of these new anode materials, cells were prepared in which (i) commercial graphite (Fig. 5a–c) or (ii) polysilyne 1 (Fig. 5d–f) was paired with Li metal in a half-cell operated at 5 °C. These cells were subjected to deep Li insertion to 0.05 V and then extracted for SEM observation. After the first Li insertion at 10 mA·g−1, the graphite electrode was covered with thin mossy Li compounds or a solid electrolyte interface (Fig. 5b). Furthermore, when the applied current density was increased to 100 mA·g−1, the mossy layer grew very thick (Fig. 5c) and individual graphite particles could not be clearly observed in the anode. The situation was very different with polysilyne 1. After the first Li insertion at a rate of 10 mA·g−1, neither mossy Li compounds nor a solid electrolyte interface was clearly observed on the electrode surface (Fig. 5e), similarly to that of the initial polysilyne 1 (Fig. 5d). Even after applying a current density of 100 mA·g−1, individual particles of polysilyne 1 could still be observed, although very thin mossy Li compounds covered the electrode. The lack of Li compound formation on the polysilyne electrode is attributed to the moderate Li insertion potential of approximately 1 V. Due to the polymeric silicon structure of polysilyne 1, the electrolyte wetted both the outside and inside surfaces of the anode, which had a highly lipophilic character. Thus, it is thought that the mobility of the Li ions in the polysilyne anode was higher than that in the graphite anode. In addition, the potential for Li insertion is very close to that of Li metal formation for the graphite anode, and therefore, Li compounds readily formed on the electrode surface. The stability of the anode material surface is known to be important for battery cycling and safety. Thus, the present results suggest that polysilyne is a suitable anode material for LIBs operated at low temperatures or high rates due to its stability.


Improving battery safety by reducing the formation of Li dendrites with the use of amorphous silicon polymer anodes.

Maruyama H, Nakano H, Ogawa M, Nakamoto M, Ohta T, Sekiguchi A - Sci Rep (2015)

SEM images of different anodes before and after Li insertion.Initial surface of anodes based on (a) graphite and (d) poly(methylsilyne) 1. SEM images of (b,c) graphite and (e,f) poly(methylsilyne) 1 after Li insertion at 10 mA·g−1 and 100 mA·g−1, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528197&req=5

f5: SEM images of different anodes before and after Li insertion.Initial surface of anodes based on (a) graphite and (d) poly(methylsilyne) 1. SEM images of (b,c) graphite and (e,f) poly(methylsilyne) 1 after Li insertion at 10 mA·g−1 and 100 mA·g−1, respectively.
Mentions: Finally, to assess the low-temperature performances of these new anode materials, cells were prepared in which (i) commercial graphite (Fig. 5a–c) or (ii) polysilyne 1 (Fig. 5d–f) was paired with Li metal in a half-cell operated at 5 °C. These cells were subjected to deep Li insertion to 0.05 V and then extracted for SEM observation. After the first Li insertion at 10 mA·g−1, the graphite electrode was covered with thin mossy Li compounds or a solid electrolyte interface (Fig. 5b). Furthermore, when the applied current density was increased to 100 mA·g−1, the mossy layer grew very thick (Fig. 5c) and individual graphite particles could not be clearly observed in the anode. The situation was very different with polysilyne 1. After the first Li insertion at a rate of 10 mA·g−1, neither mossy Li compounds nor a solid electrolyte interface was clearly observed on the electrode surface (Fig. 5e), similarly to that of the initial polysilyne 1 (Fig. 5d). Even after applying a current density of 100 mA·g−1, individual particles of polysilyne 1 could still be observed, although very thin mossy Li compounds covered the electrode. The lack of Li compound formation on the polysilyne electrode is attributed to the moderate Li insertion potential of approximately 1 V. Due to the polymeric silicon structure of polysilyne 1, the electrolyte wetted both the outside and inside surfaces of the anode, which had a highly lipophilic character. Thus, it is thought that the mobility of the Li ions in the polysilyne anode was higher than that in the graphite anode. In addition, the potential for Li insertion is very close to that of Li metal formation for the graphite anode, and therefore, Li compounds readily formed on the electrode surface. The stability of the anode material surface is known to be important for battery cycling and safety. Thus, the present results suggest that polysilyne is a suitable anode material for LIBs operated at low temperatures or high rates due to its stability.

Bottom Line: The currently used anode materials have low redox voltages that are very close to the redox potential for the formation of Li metal, which leads to severe short circuiting.Equally as significant, poly(methylsilyne) and poly(phenylsilyne) are capable of reacting with 0.45 and 0.9 Li atoms per formula unit, respectively, at an average voltage of approximately 1.0 V, affording reversible capacities of 244 mAh·g(-1) and 180 mAh·g(-1).Moreover, noteworthy is the fact that polysilynes are suitable for practical applications because they can be prepared through a simple and low-cost process and are easy to handle.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.

ABSTRACT
To provide safe lithium-ion batteries (LIBs) at low cost, battery materials which lead to reduced Li dendrite formation are needed. The currently used anode materials have low redox voltages that are very close to the redox potential for the formation of Li metal, which leads to severe short circuiting. Herein, we report that when the three-dimensional amorphous silicon polymers poly(methylsilyne) and poly(phenylsilyne) are used as anode materials, dendritic Li formation on the anode surface is avoided up to a practical current density of 10 mA·g(-1) at 5 °C. Equally as significant, poly(methylsilyne) and poly(phenylsilyne) are capable of reacting with 0.45 and 0.9 Li atoms per formula unit, respectively, at an average voltage of approximately 1.0 V, affording reversible capacities of 244 mAh·g(-1) and 180 mAh·g(-1). Moreover, noteworthy is the fact that polysilynes are suitable for practical applications because they can be prepared through a simple and low-cost process and are easy to handle.

No MeSH data available.


Related in: MedlinePlus