Carbonaceous-Material-Induced Gelation of Concentrated Electrolyte Solutions for Application in Lithium-Sulfur Battery Cathodes

Multifunctional heterostructured CoS2@Co3O4 nanosheets synergistically enhance polysulfide adsorption and conversion in lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries faces numerous challenges, primarily due to the shuttle effect of soluble lithium polysulfides (LiPSs) and the sluggish electrochemical reaction kinetics during their conversion to Li2S, resulting in poor cycling performance. To address these issues, this study employed a vapor deposition technique to in situ construct a CoS2@Co3O4 heterostructure with superior interfacial properties on a Co3O4 substrate, followed by crosslinking and optimization with reduced graphene oxide (rGO). Density functional theory (DFT) calculations reveal for the first time that the incorporation of S effectively modulates the d-band center of Co, which not only enhances the chemical adsorption capability of the heterointerface toward lithium polysulfides but also optimizes the catalytic pathway for sulfur species conversion. Comprehensive experimental results and theoretical calculations confirm that the CoS2@Co3O4 heterostructure exhibits multiple advantages, including strong adsorption capability, high catalytic activity, rapid Li+ transport efficiency, and excellent electrical conductivity. The CoS2@Co3O4 heterostructure not only significantly suppresses the LiPSs shuttle effect but also greatly accelerates the electrochemical reaction kinetics of LiPSs and Li2S. Compared to materials composed solely of CoS2 or Co3O4, the CoS2@Co3O4 heterostructure demonstrates synergistically enhanced electrochemical performance in Li-S batteries. At a current density of 2C, a representative Li-S battery achieves nearly 100 % Coulombic efficiency, with a reversible specific capacity of 827 mAh g-1 retained after 1000 cycles, corresponding to a capacity decay rate of only 0.007 % per cycle. Even under high sulfur loading conditions (5.1 mg cm-2), the battery maintains stable cycling performance. This work provides novel insights and directions for designing multifunctional heterostructures with synergistic effects for applications in lithium-ion batteries and catalytic fields.

Optimizing cation-π force fields for molecular dynamics studies of competitive solvation in conjugated organosulfur polymers for lithium-sulfur batteries

Lithium-sulfur (Li/S) batteries are emerging as a next-generation energy storage technology due to their high theoretical energy density and cost-effectiveness. π-Conjugated organosulfur polymers, such as poly(4-(thiophene-3-yl)benzenethiol) (PTBT), have shown promise in overcoming challenges such as the polysulfide shuttle effect by providing a conductive framework and enabling sulfur copolymerization. In these cathodes, cation-π interactions significantly influence Li+ diffusion and storage properties in π-conjugated cathodes, but classical OPLS-AA force fields fail to capture these effects. This study employs a bottom-up approach based on density functional theory (DFT) to optimize the nonbonded interaction parameters (OPLS-AA/corr.), particularly for the Li+-π interactions with the PTBT polymer. Following prior work, we used an ion-induced dipole potential to model the cation-π interactions. The impact of the solvent on the PTBT monomers was examined by computing the potential of mean force (PMF) between PTBT monomers and Li+ ions in both explicit and implicit solvents using the Boltzmann inversion of probability distributions close to room temperature. In the implicit solvent case, the magnitude of the binding free energy decreased with increasing dielectric constant, as the dominant electrostatics scaled with the dielectric constant. In contrast, in the explicit solvent case, considering the mixtures of organic solvent DME and DOL, the binding free energy shows minimal dependence on solvent composition due to the competing interaction of TBT and Li+ with the solvent molecules. However, increasing salt concentration decreases the binding free energy due to Debye-Hückel screening effects. In general, this work suggests that the optimized parameters can be widely used in the simulation of polymers in electrolytes for the Li/S battery to enhance the representation of cation-π interactions for a fixed charge force field.

Defect-rich Mo2S3 loaded wood-derived carbon acts as a spacer in lithium-sulfur batteries: forming a polysulfide capture net and promoting fast lithium flux

Due to the sluggish kinetics of sulfur conversion and the large volume change of the lithium anode, along with the formation of lithium dendrites, lithium-sulfur batteries (LSBs) usually exhibit severe capacity decay and poor cycle life. It is necessary to consider the factors associated with cathodes, separators and anodes in an integrated manner to solve the problems existing in LSBs. In this paper, a vertically aligned porous carbon decorated with transition metal sulfides was introduced between a cathode and an anode to comprehensively solve the problems of LSBs. Widely existing natural wood was used as the framework structure, and Mo₂S₃ with abundant sulfur vacancies was deposited into its channels. Theoretical calculations and experimental results have confirmed a low energy barrier for sulfur conversion and the presence of a strong electric field around the spacer, which benefits fast ion transportation. As a result, on employing the multifunctional spacer, LSB full cells delivered a high initial capacity and a long cycle life. This study provides a reference for reducing development cost, simplifying optimization steps and promoting the commercial application of LSBs.