Xanthogen Polysulfides as a New Class of Electrode Material for Rechargeable Batteries

Abstract

electrochemical reversibility. In addition to their favorable redox behavior, these compounds are also naturally abundant, environmentally friendly, inexpensive, and easy to process into battery electrodes. [12] While sulfur offers a high energy density exceeding 2500 W h kg −1 , it is beleaguered by three major issues. First, the electrical conductivity of sulfur is extremely low, necessitating the addition of a large amount of conductive hosts (e.g., carbon) in the battery electrode. Second, the difference in density between sulfur and its discharge product, Li 2 S, is quite large. This results in a volume change of nearly 80% during cycling, thus requiring a cathode structure to accommodate the large volume fluctuation and the resulting stresses generated. Third, the lithium polysulfides formed during cycling are electrolyte-soluble and thus shuttle between the electrodes. This "shuttle effect" results in a loss of active material, poor Coulombic efficiency, and short cycle life. [8] On the other hand, organic compounds (e.g., carbonyls, organosulfides, imines, and nitriles) present three distinct advantages. First, the functional groups in the organic moieties can alter the physical properties of these materials including their electrical conductivity. [9] Second, the difference in density between the delithiated and the lithiated forms of these compounds is low, resulting in a smaller volume change and stress in the cathode. [13] Finally, the bulkiness and polarity of the organic functional groups can be used to alter their solubility in the electrolyte, thus minimizing parasitic shuttle effects. [12,14] Organosulfur compounds combine the multi-electron, highenergy-density characteristics of sulfur with the distinct advantages of organic compounds. Specifically, the ability to tune the physical and chemical properties of organosulfur materials with various functional groups allows for optimization of their conductivity, solubility, and density. [9,15-17] Recognizing these advantages, various organosulfur compounds have been reported since the late 1980s. [18,19] Early reports of such materials focused on polymers that functioned according to the disulfide-thiolate redox behavior. [19,20] More recently, polymers containing multiple SS bonds that have been synthesized through inverse vulcanization, [21,22] incorporation of covalent frameworks, [22-25] and condensation reactions have been reported. [26-29] In addition to polymers, linear compounds, [15,30,31] cyclics, [32] hybrids, [33,34] and compounds with unique functional groups have also been reported. [35-37] Organosulfides are an emerging class of alternative sulfur-based cathode materials. This work explores a new member in this family of active materials, viz., xanthogen polysulfides. Diisopropyl xanthogen polysulfide (DIXPS) is used as a model compound in a lithium battery to understand the chemical changes and the unique electrochemical behavior of this class of materials by employing various materials characterization methodologies. As a cathode ma...

Progress and Perspectives of Organosulfur for Lithium–Sulfur Batteries

“…Xanthogen polysulfides have a formula of R-O-C(S)-S-S n -S-(S)C-O-R, where R is an alkyl or aryl group, n is the number of sulfur atoms and C(S) is a double bond between C and S (Figure 2a). [28] The materials with different numbers of sulfur atoms were synthesized and characterized: di-isopropyl xanthogen disulfide (DIXDS) and di-isopropyl xanthogen polysulfide (DIXPS). The number of sulfur atoms affects both physical and electrochemical properties of these compounds.…”

Advances of Organosulfur Materials for Rechargeable Metal Batteries

“…Another two organosulfur model compounds are diisopropyl xanthogen disulfide (DIXDS) and diisopropyl xanthogen polysulfide (DIXPS) studied by Bhargav and Manthiram. [ 20 ] Each DIXPS molecule can take 10 Li + and e − as shown in Figure 5 a , offering a high theoretical specific capacity of 672 mAh g −1 and specific energy of 1546 Wh kg −1 . In a Li cell, it exhibits three discharge voltage plateaus at 2.61, 2.30, and 2.08 V with the initial discharge specific capacity of 628 mAh g −1 (93.5% of the theoretical capacity) at C/10 rate (Figure 5b ), offering a high energy density of 1313 Wh kg −1 and 1694 Wh L −1 .…”

“…b) Voltage profile of Li/DIXPS and Li/DIXDS cells at C/10 rate. Reproduced with permission [20]. Copyright 2020, Wiley-VCH.…”

Smart Flow Electrosynthesis and Application of Organodisulfides in Redox Flow Batteries

“…Isopropylxanthic disulfide (IXDS), an important molecule in vulcanization accelerators, flotation agent, and energy materials, [11] was chosen to explain the SFE process. Typical synthesis process for IXDS involves two steps (Figure S3, Supporting Information): 1) a condensation reaction of isopropanol with alkali-metal hydroxide and carbon disulfide (CS 2 ) to form sodium isobutyl xanthate 2) which was oxidized by oxidizing agents (e.g., H 2 O 2 , K 2 S 2 O 8 , and I 2 ).…”