Inverse Vulcanization Research Articles

Structural origins of enhanced capacity retention in novel copolymerized sulfur-based composite cathodes for high-energy density Li-S batteries

Poly[sulfur-random-1,3-diisopropenylbenzene (DIB)] copolymers synthesized via inverse vulcanization form electrochemically active polymers used as cathodes for high-energy density Li-S batteries, capable of enhanced capacity retention (1005 mAh/g at 100 cycles) and lifetimes of over 500 cycles. In this prospective, we demonstrate how analytical electron microscopy can be employed as a powerful tool to explore the origins of the enhanced capacity retention. We analyze morphological and compositional features when the copolymers, with DIB contents up to 50% by mass, are blended with carbon nanoparticles. Replacing the elemental sulfur with the copolymers improves the compatibility and interfacial contact between active sulfur compounds and conductive carbons. There also appears to be improvements of the cathode mechanical stability that leads to less cracking but preserving porosity. This compatibilization scheme through stabilized organosulfur copolymers represents an alternative strategy to the nanoscale encapsulation schemes which are often used to improve the cycle life in high-energy density Li-S batteries.

Improving the Charge Conductance of Elemental Sulfur via Tandem Inverse Vulcanization and Electropolymerization.

The synthesis of polymeric materials using elemental sulfur (S8) as the chemical feedstock has recently been developed using a process termed inverse vulcanization. The preparation of chemically stable sulfur copolymers was previously prepared by the inverse vulcanization of S8 and 1,3-diisopropenylbenzene (DIB); however, the development of synthetic methods to introduce new chemical functionality into this novel class of polymers remains an important challenge. In this report the introduction of polythiophene segments into poly(sulfur-random-1,3-diisopropenylbenzene) is achieved by the inverse vulcanization of S8 with a styrenic functional 3,4-propylenedioxythiophene (ProDOT-Sty) and DIB, followed by electropolymerization of ProDOT side chains. This methodology demonstrates for the first time a facile approach to introduce new functionality into sulfur and high sulfur content polymers, while specifically enhancing the charge conductivity of these intrinsically highly resistive materials.

Nanoparticle-sulphur "inverse vulcanisation" polymer composites.

Composites of sulphur polymers with nanoparticles such as PbS, with tunable optical properties are reported. A hydrothermal route incorporating pre-formed nanoparticles was used, and their physical and chemical properties evaluated by transmission and scanning electron microscopy, thermogravimetric and elemental analyses. These polymers are easily synthesised from an industrial waste material, elemental sulphur, can be cast into virtually any form and as such represent a new class of materials designed for a responsible energy future.

Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li–S batteries

High sulfur content copolymers were prepared via inverse vulcanization of sulfur with 1,4-diphenylbutadiyne (DiPhDY) for use as the active cathode material in lithium–sulfur batteries.

Preparation of Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur.

The synthesis of dynamic covalent polymers with controllable amounts of sulfur-sulfur (S-S) bonds in the polymer backbone via inverse vulcanization of elemental sulfur (S8) and 1,3-diisopropenylbenzene (DIB) is reported. An attractive feature of the inverse vulcanization process is the ability to control the number and dynamic nature of S-S bonds in poly(sulfur-random-(1,3-diisopropenylbenzene)) (poly(S-r-DIB) copolymers by simple variation of S8/DIB feed ratios in the copolymerization. S-S bonds in poly(S-r-DIB) copolymers of high sulfur content and sulfur rank were found to be more dynamic upon exposure to either heat, or mechanical stimuli. Interrogation of dynamic S-S bonds was conducted in the solid-state utilizing electron paramagnetic resonance spectroscopy and in situ rheological measurements. Time-dependent rheological property behavior demonstrated a compositional dependence of the healing behavior in the copolymers, with the highest sulfur (80 wt % sulfur) content affording the most rapid dynamic response and recovery of rheological properties.

Characterization of Polymerized Sulfur Cathodes upon Cycling

Rechargeable Li-S batteries offer an unprecedented opportunity for energy storage technology. Sulfur is a very cheap material with remarkably high energy storage density when used as a cathode. Sulfur cathodes have historically suffered from a myriad of problems, including low active material utilization due to low electronic conductivity and significant capacity fade upon cycling due to polysulfide dissolution and cracking of the cathode. The main approach for improving active material utilization and maintaining capacity has been to sequester sulfur within various forms of electronically conductive, nanostructured carbons. Recently, researchers have developed a copolymer with a very high sulfur content via a process termed inverse vulcanization.1 The sulfur-containing polymer is inexpensive to produce, and full Li-S cells utilizing this copolymer in the cathode achieve capacities of 635 mAhr/g after 500 cycles at a rate of C/10.2 This talk will focus on results of characterization studies to determine the morphology and composition of the sulfur copolymer cathode and electrolyte solution during the cycling process. Microscopy studies show that the sulfur copolymer cathode maintains greater uniformity and shows less cracking upon cycling than an elemental sulfur cathode. We will also report on results of in-situ Raman and XPS studies to identify the products present in the cathode and in the electrolyte at various potentials during cycling.1. J. Pyun et. al., Nature Chemistry, 5:518-524, 2013.2. J. Pyun, et. al., ACS Macro Letters, 3:229-232, 2014.

Kilogram scale inverse vulcanization of elemental sulfur to prepare high capacity polymer electrodes for Li‐S batteries

ABSTRACTThe synthesis of high content sulfur copolymers via the inverse vulcanization of elemental sulfur and 1,3‐diisopropenylbenzene (DIB) on a one‐kilogram scale is reported in a single step process. Investigation into the effects of temperature, reaction scale, and comonomer feed ratios on the inverse vulcanization process of S8 and DIB were explored to suppress the Trommsdorf effect and enable large scale synthesis of these copolymers. The copolymers were then successfully used as the active cathode materials in Li‐S batteries, exhibiting enhanced capacity retention and battery lifetimes (608 mAh/g at 640 cycles) at a C/10 rate. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 173–177

New Infrared Transmitting Material via Inverse Vulcanization of Elemental Sulfur to Prepare High Refractive Index Polymers

Polymers for IR imaging: The preparation of high refractive index polymers (n = 1.75 to 1.86) via the inverse vulcanization of elemental sulfur is reported. High quality imaging in the near (1.5 μm) and mid-IR (3-5 μm) regions using high refractive index polymeric lenses from these sulfur materials was demonstrated.

Inverse Vulcanization of Elemental Sulfur to Prepare Polymeric Electrode Materials for Li-S Batteries.

Sulfur-rich copolymers based on poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r-DIB)) were synthesized via inverse vulcanization to create cathode materials for lithium-sulfur battery applications. These materials exhibit enhanced capacity retention (1005 mAh/g at 100 cycles) and battery lifetimes over 500 cycles at a C/10 rate. These poly(S-r-DIB) copolymers represent a new class of polymeric electrode materials that exhibit one of the highest charge capacities reported, particularly after extended charge-discharge cycling in Li-S batteries.

A new trick to harness the sulfur surplus

In the early-to-mid 1800s, Charles Goodyear1 discovered that natural rubbers became more robust when heated in the presence of a small amount of sulfur. We now know that this ‘vulcanization’ process stems from sulfur’s ability to form chemical bridges that strengthen the polymer chains in the rubber and is routinely used to produce tires among other common goods. An international team from the University of Arizona, Seoul National University, the University of Hamburg, and the University of Delaware developed what they refer to as ‘inverse vulcanization’.2 In this process, sulfur is used as the primary ingredient and reinforced with a stryenic additive. The method involves adding 1,3-diisopropenylbenzene (DIB), which effectively intercepted radicals formed at elevated temperatures and afforded useful copolymeric materials enriched with sulfur. The real trick, however, was timing: adding the DIB after the sulfur was liquefied and in its reactive form appeared to be critical. The ratio of DIB-to-sulfur was also an important factor as the physical, electronic and optical properties displayed by the composites were dependent on their elemental compositions.

The use of elemental sulfur as an alternative feedstock for polymeric materials

An excess of elemental sulfur is generated annually from hydrodesulfurization in petroleum refining processes; however, it has a limited number of uses, of which one example is the production of sulfuric acid. Despite this excess, the development of synthetic and processing methods to convert elemental sulfur into useful chemical substances has not been investigated widely. Here we report a facile method (termed 'inverse vulcanization') to prepare chemically stable and processable polymeric materials through the direct copolymerization of elemental sulfur with vinylic monomers. This methodology enabled the modification of sulfur into processable copolymer forms with tunable thermomechanical properties, which leads to well-defined sulfur-rich micropatterned films created by imprint lithography. We also demonstrate that these copolymers exhibit comparable electrochemical properties to elemental sulfur and could serve as the active material in Li-S batteries, exhibiting high specific capacity (823 mA h g(-1) at 100 cycles) and enhanced capacity retention.