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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

Structural evolution of polysilynes during lithiation.Diffuse reflectance UV-vis spectra of (a) poly(methylsilyne) 1 and (b) poly(phenylsilyne) 2. Corresponding photos for each sample are also shown (insets). Colour change with lithiation was observed. XRD patterns of (c) poly(methylsilyne) 1 and (d) poly(phenylsilyne) 2. Blue, green and red lines are initial pattern and patterns for SiR/nLi (n = 0.5) and SiR/nLi (n = 1.0), respectively. Black dotted lines represent XRD cell holder.
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f4: Structural evolution of polysilynes during lithiation.Diffuse reflectance UV-vis spectra of (a) poly(methylsilyne) 1 and (b) poly(phenylsilyne) 2. Corresponding photos for each sample are also shown (insets). Colour change with lithiation was observed. XRD patterns of (c) poly(methylsilyne) 1 and (d) poly(phenylsilyne) 2. Blue, green and red lines are initial pattern and patterns for SiR/nLi (n = 0.5) and SiR/nLi (n = 1.0), respectively. Black dotted lines represent XRD cell holder.

Mentions: Poly(methylsilyne) 1 exhibited a strong absorption band in the UV region with an edge at 450 nm (3.0 eV), which is in agreement with that of the previously reported Si polymer (Fig. 4a). After the mechanochemical reaction, the absorption band edge of polysilyne 1/0.5 Li shifted to a longer wavelength and exhibited a lower bandgap energy (0.8 eV). Increasing the Li content to yield polysilyne 1/1.0 Li did not result in a further shift of this absorption peak, suggesting that the Li storage capacity of 1 is saturated above a composition of 1/0.5 Li. Poly(phenylsilyne) 2 exhibited an absorption band edge at 490 nm (2.8 eV) very similar to that of poly(methylsilyne) 1 (Fig. 4b). After milling 2 with 0.5 Li, both polysilyne 2 and polysilyne 2/0.5 Li-like moieties coexisted in the composite due to the inhomogeneous distribution of Li in polysilyne 2/0.5 Li. However, when an equal amount of Li was added to generate polysilyne 2/1.0 Li, the peak shape drastically changed and exhibited an absorption edge at 0.8 eV. In addition, in the XRD patterns shown in Fig. 4c,d, it can be seen that the peak shift for n = 0.5 for polysilyne 1/n Li is saturated at 2θ = 8.0°, while the peak for polysilyne 2 shifts continuously to 2θ = 6.6° from 7.2° as the amount of added Li increases. These results agree well with those obtained from the electrochemical Li insertion reaction analysis, for which values of 0.45 Li per formula unit and 0.9 Li per formula unit of polysilyne 1 and polysilyne 2, respectively, were determined. In other words, the quantity of Li that could be inserted increased when the polysilyne included an organic substituent that expanded the cage size. Furthermore, these results indicate the formation of new electron band levels following lithiation of the polysilynes. This property renders the polysilynes suitable for use as anode materials, because their conductivities increase during the Li insertion process.


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)

Structural evolution of polysilynes during lithiation.Diffuse reflectance UV-vis spectra of (a) poly(methylsilyne) 1 and (b) poly(phenylsilyne) 2. Corresponding photos for each sample are also shown (insets). Colour change with lithiation was observed. XRD patterns of (c) poly(methylsilyne) 1 and (d) poly(phenylsilyne) 2. Blue, green and red lines are initial pattern and patterns for SiR/nLi (n = 0.5) and SiR/nLi (n = 1.0), respectively. Black dotted lines represent XRD cell holder.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Structural evolution of polysilynes during lithiation.Diffuse reflectance UV-vis spectra of (a) poly(methylsilyne) 1 and (b) poly(phenylsilyne) 2. Corresponding photos for each sample are also shown (insets). Colour change with lithiation was observed. XRD patterns of (c) poly(methylsilyne) 1 and (d) poly(phenylsilyne) 2. Blue, green and red lines are initial pattern and patterns for SiR/nLi (n = 0.5) and SiR/nLi (n = 1.0), respectively. Black dotted lines represent XRD cell holder.
Mentions: Poly(methylsilyne) 1 exhibited a strong absorption band in the UV region with an edge at 450 nm (3.0 eV), which is in agreement with that of the previously reported Si polymer (Fig. 4a). After the mechanochemical reaction, the absorption band edge of polysilyne 1/0.5 Li shifted to a longer wavelength and exhibited a lower bandgap energy (0.8 eV). Increasing the Li content to yield polysilyne 1/1.0 Li did not result in a further shift of this absorption peak, suggesting that the Li storage capacity of 1 is saturated above a composition of 1/0.5 Li. Poly(phenylsilyne) 2 exhibited an absorption band edge at 490 nm (2.8 eV) very similar to that of poly(methylsilyne) 1 (Fig. 4b). After milling 2 with 0.5 Li, both polysilyne 2 and polysilyne 2/0.5 Li-like moieties coexisted in the composite due to the inhomogeneous distribution of Li in polysilyne 2/0.5 Li. However, when an equal amount of Li was added to generate polysilyne 2/1.0 Li, the peak shape drastically changed and exhibited an absorption edge at 0.8 eV. In addition, in the XRD patterns shown in Fig. 4c,d, it can be seen that the peak shift for n = 0.5 for polysilyne 1/n Li is saturated at 2θ = 8.0°, while the peak for polysilyne 2 shifts continuously to 2θ = 6.6° from 7.2° as the amount of added Li increases. These results agree well with those obtained from the electrochemical Li insertion reaction analysis, for which values of 0.45 Li per formula unit and 0.9 Li per formula unit of polysilyne 1 and polysilyne 2, respectively, were determined. In other words, the quantity of Li that could be inserted increased when the polysilyne included an organic substituent that expanded the cage size. Furthermore, these results indicate the formation of new electron band levels following lithiation of the polysilynes. This property renders the polysilynes suitable for use as anode materials, because their conductivities increase during the Li insertion process.

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