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Synthesis of three-dimensionally interconnected sulfur-rich polymers for cathode materials of high-rate lithium-sulfur batteries.

Kim H, Lee J, Ahn H, Kim O, Park MJ - Nat Commun (2015)

Bottom Line: Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases.Our lithium-sulfur cells display discharge capacity of 945 mAh g(-1) after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles.Particularly, the organized amine groups in the crystals increase Li(+)-ion transfer rate, affording a rate performance of 1210, mAh g(-1) at 0.1 C and 730 mAh g(-1) at 5 C.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.

ABSTRACT
Elemental sulfur is one of the most attractive cathode active materials in lithium batteries because of its high theoretical specific capacity. Despite the positive aspect, lithium-sulfur batteries have suffered from severe capacity fading and limited rate capability. Here we report facile large-scale synthesis of a class of organosulfur compounds that could open a new chapter in designing cathode materials to advance lithium-sulfur battery technologies. Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases. Our lithium-sulfur cells display discharge capacity of 945 mAh g(-1) after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles. Particularly, the organized amine groups in the crystals increase Li(+)-ion transfer rate, affording a rate performance of 1210, mAh g(-1) at 0.1 C and 730 mAh g(-1) at 5 C.

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Crystal structure analysis.Powder XRD profiles of (a) the as-prepared TTCA-I and TTCA-II co-crystals, (b) the heat-treated TTCA-I and TTCA-II at 160 °C and (c) the vulcanized S-TTCA-I and S-TTCA-II at 245 °C. Miller indices of the reflection plane hkl are given in each figure.
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f4: Crystal structure analysis.Powder XRD profiles of (a) the as-prepared TTCA-I and TTCA-II co-crystals, (b) the heat-treated TTCA-I and TTCA-II at 160 °C and (c) the vulcanized S-TTCA-I and S-TTCA-II at 245 °C. Miller indices of the reflection plane hkl are given in each figure.

Mentions: To determine the changes in crystal structures as a result of heat treatment and vulcanization, a set of powder X-ray diffraction (XRD) profiles that used a 2θ scan range of 5−35° with a 0.02° step interval are presented in Fig. 4a–c. As shown in Fig. 4a, TTCA-I initially had a monoclinic P21/c space group, while a triclinic P1 space group was determined for TTCA-II. The unit cell parameters obtained from the Cambridge Structural Database are a=9.780 Å, b=12.755 Å, c=9.280 Å, α= 90.00°, β=91.19° and γ=90.00° for TTCA-I; and a=8.937 Å, b=9.985 Å, c=10.447 Å, α=95.12°, β=96.79° and γ=107.29° for TTCA-II46. Elimination of solvent from TTCA-I and TTCA-II then leads to structural transformation into identical triclinic structures with a space group (Fig. 4b) having the unit cell parameters a=5.587 Å, b=7.047 Å, c=8.799 Å, α=102.99°, β=92.87° and γ=110.47°. The emergence of porous morphologies is thus ascribed to shrinkage of the cell volume, where the degree of reduction for TTCA-I and TTCA-II is different. This should be closely related with the surface area (pore volume) of heat-treated TTCA frameworks. Finally, S-TTCA-I and S-TTCA-II displayed featureless XRD patterns, as shown in Fig. 4c, denoting that the covalent attachment of sulfur into TTCA frameworks destroyed the long-ranged π–π stacking of TTCA rings. Given that the crystalline peaks of both TTCA and elemental sulfur remain intact after sulfur impregnation at 160 °C (Supplementary Fig. 3), the absence of sulfur crystal peaks after vulcanization (Fig. 4c) should be noteworthy. This implies that the sulfur in S-TTCA exists in an amorphous state, as it was involved in the polymerization. Note that the TTCA crystals were thermally stable (see the temperature-dependent XRD profiles in Supplementary Fig. 4), and therefore, the loss of crystallinity of S-TTCA is not ascribed to the amorphization of TTCA.


Synthesis of three-dimensionally interconnected sulfur-rich polymers for cathode materials of high-rate lithium-sulfur batteries.

Kim H, Lee J, Ahn H, Kim O, Park MJ - Nat Commun (2015)

Crystal structure analysis.Powder XRD profiles of (a) the as-prepared TTCA-I and TTCA-II co-crystals, (b) the heat-treated TTCA-I and TTCA-II at 160 °C and (c) the vulcanized S-TTCA-I and S-TTCA-II at 245 °C. Miller indices of the reflection plane hkl are given in each figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490390&req=5

f4: Crystal structure analysis.Powder XRD profiles of (a) the as-prepared TTCA-I and TTCA-II co-crystals, (b) the heat-treated TTCA-I and TTCA-II at 160 °C and (c) the vulcanized S-TTCA-I and S-TTCA-II at 245 °C. Miller indices of the reflection plane hkl are given in each figure.
Mentions: To determine the changes in crystal structures as a result of heat treatment and vulcanization, a set of powder X-ray diffraction (XRD) profiles that used a 2θ scan range of 5−35° with a 0.02° step interval are presented in Fig. 4a–c. As shown in Fig. 4a, TTCA-I initially had a monoclinic P21/c space group, while a triclinic P1 space group was determined for TTCA-II. The unit cell parameters obtained from the Cambridge Structural Database are a=9.780 Å, b=12.755 Å, c=9.280 Å, α= 90.00°, β=91.19° and γ=90.00° for TTCA-I; and a=8.937 Å, b=9.985 Å, c=10.447 Å, α=95.12°, β=96.79° and γ=107.29° for TTCA-II46. Elimination of solvent from TTCA-I and TTCA-II then leads to structural transformation into identical triclinic structures with a space group (Fig. 4b) having the unit cell parameters a=5.587 Å, b=7.047 Å, c=8.799 Å, α=102.99°, β=92.87° and γ=110.47°. The emergence of porous morphologies is thus ascribed to shrinkage of the cell volume, where the degree of reduction for TTCA-I and TTCA-II is different. This should be closely related with the surface area (pore volume) of heat-treated TTCA frameworks. Finally, S-TTCA-I and S-TTCA-II displayed featureless XRD patterns, as shown in Fig. 4c, denoting that the covalent attachment of sulfur into TTCA frameworks destroyed the long-ranged π–π stacking of TTCA rings. Given that the crystalline peaks of both TTCA and elemental sulfur remain intact after sulfur impregnation at 160 °C (Supplementary Fig. 3), the absence of sulfur crystal peaks after vulcanization (Fig. 4c) should be noteworthy. This implies that the sulfur in S-TTCA exists in an amorphous state, as it was involved in the polymerization. Note that the TTCA crystals were thermally stable (see the temperature-dependent XRD profiles in Supplementary Fig. 4), and therefore, the loss of crystallinity of S-TTCA is not ascribed to the amorphization of TTCA.

Bottom Line: Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases.Our lithium-sulfur cells display discharge capacity of 945 mAh g(-1) after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles.Particularly, the organized amine groups in the crystals increase Li(+)-ion transfer rate, affording a rate performance of 1210, mAh g(-1) at 0.1 C and 730 mAh g(-1) at 5 C.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.

ABSTRACT
Elemental sulfur is one of the most attractive cathode active materials in lithium batteries because of its high theoretical specific capacity. Despite the positive aspect, lithium-sulfur batteries have suffered from severe capacity fading and limited rate capability. Here we report facile large-scale synthesis of a class of organosulfur compounds that could open a new chapter in designing cathode materials to advance lithium-sulfur battery technologies. Porous trithiocyanuric acid crystals are synthesized for use as a soft template, where the ring-opening polymerization of elemental sulfur takes place along the thiol surfaces to create three-dimensionally interconnected sulfur-rich phases. Our lithium-sulfur cells display discharge capacity of 945 mAh g(-1) after 100 cycles at 0.2 C with high-capacity retention of 92%, as well as lifetimes of 450 cycles. Particularly, the organized amine groups in the crystals increase Li(+)-ion transfer rate, affording a rate performance of 1210, mAh g(-1) at 0.1 C and 730 mAh g(-1) at 5 C.

No MeSH data available.


Related in: MedlinePlus