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1. Chemistry‐Performance Relationships of Polymer Gel‐Electrolytes for Mg−S and Li−S Batteries: Influence of Network Cation Solvation Capacity on Polymer‐Polysulfide Interactions

   https://doi.org/10.1002/cphc.202100881  

   Ford, Hunter_O; He, Peng; Schaefer, Jennifer_L (February 2022, ChemPhysChem)

   Abstract Metal‐sulfur batteries are a promising next‐generation energy storage technology, offering high theoretical energy densities with low cost and good sustainability. An active area of research is the development of electrolytes that address unwanted migration of sulfur and intermediate species known as polysulfides during operation of metal‐sulfur batteries, a phenomenon that leads to low energy efficiency and short life‐spans. A particular class of electrolytes, gel polymer electrolytes, are especially attractive for their ability to repel polysulfides on the basis of structure, electrostatics, and other polymer properties. Herein, within the context of magnesium‐ and lithium‐sulfur batteries, we investigate the impact of gel polymer electrolyte cation solvation capacity, a property related to network dielectric constant and chemistry, on sulfur/polysulfide‐polymer interactions, an understudied property‐performance relationship. Polymers with lower cation solvation capacity are found to permanently absorb less polysulfide active material, which increases sulfur utilization for Li−S batteries and significantly increases charge efficiency and life‐span for Li−S and Mg−S batteries. 

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2. Implications of in situ chalcogen substitutions in polysulfides for rechargeable batteries

   https://doi.org/10.1039/D1EE01113H  

   Nanda, Sanjay; Bhargav, Amruth; Jiang, Zhou; Zhao, Xunhua; Liu, Yuanyue; Manthiram, Arumugam (October 2021, Energy & Environmental Science)

   The electrochemical behavior of sulfur-based batteries is intrinsically governed by polysulfide species. Here, we compare the substitutions of selenium and tellurium into polysulfide chains and demonstrate their beneficial impact on the chemistry of lithium–sulfur batteries. While selenium-substituted polysulfides enhance cathode utilization by effectively catalyzing the sulfur/Li 2 S conversion reactions due to the preferential formation of radical intermediates, tellurium-substituted polysulfides improve lithium cycling efficiency by reducing into a passivating interfacial layer on the lithium surface with low Li + -ion diffusion barriers. This unconventional strategy based on “molecular engineering” of polysulfides and exploiting the intrinsic polysulfide shuttle effect is validated by a ten-fold improvement in the cycle life of lean-electrolyte “anode-free” pouch cells. Assembled with no free lithium metal at the anode, the anode-free configuration maximizes the energy density, mitigates the challenges of handling thin lithium foils, and eliminates self-discharge upon cell assembly. The insights generated into the differences between selenium and tellurium chemistries can be applied to benefit a broad range of metal–chalcogen batteries as well as chalcogenide solid electrolytes. 

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3. Electrocatalytic and Conductive Vanadium Oxide on Carbonized Bacterial Cellulose Aerogel for the Sulfur Cathode in Li-S Batteries

   https://doi.org/10.3390/batteries9010014  

   Lin, Xueyan; Li, Wenyue; Pan, Xuan; Wang, Shu; Fan, Zhaoyang (January 2023, Batteries)

   Many transition-metal-oxide-based catalysts have been investigated to chemically bind soluble lithium polysulfides and accelerate their redox kinetics in lithium-sulfur (Li-S) battery chemistry. However, the intrinsic poor electrical conductivities of these oxides restrict their catalytic performance, consequently limiting the sulfur utilization and the rate performance of Li-S batteries. Herein, we report a freestanding electrocatalytic sulfur host consisting of hydrogen-treated VO2 nanoparticles (H-VO2) anchored on nitrogen-doped carbonized bacterial cellulose aerogels (N-CBC). The hydrogen treatment enables the formation and stabilization of the rutile VO2(R) phase with metallic conductivity at room temperature, significantly enhancing its catalytic capability compared to the as-synthesized insulative VO2(M) phase. Several measurements characterize the electrocatalytic performance of this unique H-VO2@N-CBC structure. In particular, the two kinetic barriers between S8, polysulfides, and Li2S are largely reduced by 28.2 and 43.3 kJ/mol, respectively. Accordingly, the Li-S battery performance, in terms of sulfur utilization and charge/discharge rate, is greatly improved. This work suggests an effective strategy to develop conductive catalysts based on a typical transition metal oxide (VO2) for Li-S batteries. 

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4. Lithium Tritelluride as an Electrolyte Additive for Stabilizing Lithium Deposition and Enhancing Sulfur Utilization in Anode‐Free Lithium–Sulfur Batteries

   https://doi.org/10.1002/adfm.202304568  

   Lai, Tianxing; Bhargav, Amruth; Manthiram, Arumugam (June 2023, Advanced Functional Materials)

   Abstract Despite the potential to become the next‐generation energy storage technology, practical lithium–sulfur (Li–S) batteries are still plagued by the poor cyclability of the lithium‐metal anode and sluggish conversion kinetics of S species. In this study, lithium tritelluride (LiTe₃), synthesized with a simple one‐step process, is introduced as a novel electrolyte additive for Li–S batteries. LiTe₃quickly reacts with lithium polysulfides and functions as a redox mediator to greatly improve the cathode kinetics and the utilization of active materials in the cathode. Moreover, the formation of a Li₂TeS₃/Li₂Te‐enriched interphase layer on the anode surface enhances ionic transport and stabilizes Li deposition. By regulating the chemistry on both the anode and cathode sides, this additive enables a stable operation of anode‐free Li–S batteries with only 0.1 mconcentration in conventional ether‐based electrolytes. The cell with the LiTe₃additive retains 71% of the initial capacity after 100 cycles, while the control cell retains only 23%. More importantly, with high utilization of Te, the additive enables significantly better cyclability of anode‐free pouch full‐cells under lean electrolyte conditions. 

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5. Lithium Trithiocarbonate as a Dual‐Function Electrode Material for High‐Performance Lithium–Sulfur Batteries

   https://doi.org/10.1002/aenm.202200680  

   Sul, Hyunki; Bhargav, Amruth; Manthiram, Arumugam (April 2022, Advanced Energy Materials)

   Abstract The development of practical lithium–sulfur (Li–S) batteries with prolonged cycle life and high Coulombic efficiency is limited by both parasitic reactions from dissolved polysulfides and mossy lithium deposition. To address these challenges, here lithium trithiocarbonate (Li₂CS₃)‐coated lithium sulfide (Li₂S) is employed as a dual‐function cathode material to improve the cycling performance of Li–S batteries. Interestingly, at the cathode, Li₂CS₃forms an oligomer‐structured layer on the surface to suppress polysulfide shuttle. The presence of Li₂CS₃alters the conventional sulfur reaction pathway, which is supported by material characterization and density functional theory calculation. At the anode, a stable in situ solid electrolyte interphase layer with a lower Li‐ion diffusion barrier is formed on the Li‐metal surface to engender enhanced lithium plating/stripping performance upon cycling. Consequently, the obtained anode‐free full cells with Li₂CS₃exhibit a superior capacity retention of 51% over 125 cycles, whereas conventional Li₂S cells retain only 26%. This study demonstrates that Li₂CS₃inclusion is an efficient strategy for designing high‐energy‐density Li–S batteries with extended cycle life. 

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