Modulating Electron Conducting Properties at Lithium Anode Interfaces for Durable Lithium-Sulfur Batteries

Cationic cellulose nanofiber solid electrolytes: A pathway to high lithium-ion migration and polysulfide adsorption for lithium-sulfur batteries

Polyethylene oxide (PEO) solid electrolytes, acknowledged for their safety advantages over liquid counterparts, confront inherent challenges, including low ionic conductivity, restricted lithium ion migration, and mechanical fragility, notably pronounced in lithium‑sulfur batteries due to the polysulfide shuttling phenomenon. To address these limitations, we integrate a quaternary ammonium cation-modified cellulose (QACC) nanofiber, electrospun with cellulose acetate (CA) from recycled cigarette filters, into the PEO electrolyte matrix. The nitrogen atom within the quaternary ammonium group exhibits a pronounced affinity for polysulfide compounds, effectively curtailing polysulfide migration. Concurrently, Lewis acid-base interactions between quaternary ammonium groups and lithium salt anions facilitate the release of additional Li+, achieving a lithium-ion transference number 1.5 times higher than its pure PEO counterpart. Furthermore, the introduction of a larger trifluoromethanesulfonimide (TFSI) group on the QACC macromolecule (TFSI-QACC) disrupts the ordered arrangement of PEO macromolecules, resulting in a noteworthy enhancement in ionic conductivity, reaching 2.07 × 10-4 S cm-1 at 60 °C, thus addressing the challenge of low PEO electrolyte conductivity. Moreover, the nanofiber enhances the mechanical strength of the PEO electrolyte from 0.49 to 7.50 MPa, mitigating safety concerns related to lithium dendrites puncturing the electrolyte. Consequently, the composite PEO demonstrates exemplary performance in lithium symmetrical batteries, enduring 500 h of continuous operation and completing 100 cycles at both room and elevated temperatures. This integrated approach, transitioning from waste to wealth, adeptly addresses a spectrum of challenges in the efficiency of solid-state electrolytes, holding considerable promise for advancing lithium‑sulfur battery technology.

Fluorinated Artificial Solid-Electrolyte-Interphase Layer for Long-Life Sodium Metal Batteries

Sodium metal batteries have garnered significant attention due to their high theoretical specific capacity, cost effectiveness, and abundant availability. However, the propensity for dendritic sodium formation, stemming from the highly reactive nature of the sodium metal surface, poses safety concerns, and the uncontrollable formation of the solid-electrolyte interphase (SEI) leads to large cell impedance and battery failures. In this study, we present a novel approach where we have successfully developed a stable fluorinated artificial SEI layer on the sodium metal surface by employing various weight percentages of tin fluoride in a dimethyl carbonate solution, utilizing a convenient, cost-effective, and single-step method. The resulting fluoride-rich protective layer effectively stabilized the Na metal surfaces and significantly enhanced cycling stability. The engineered artificial SEI layer demonstrated an enhanced lifetime of Na metal symmetric cells of over 3.5 times, over 700 h at the current density of 0.25 mA/cm2, in cycling performance compared to the untreated sodium, which is attributed to the suppression of dendrite formation and the reduction of undesired SEI formation during high-current cycling.

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.