Thermoelectric GNP-Integrated MoS₂/S Cathodes for Mg-S Batteries with a Li₂CO₃-Modified Halogen-Free Electrolyte.

Authors

Lamiaa El-Sherif, Awad Bakry, Mustafa Abdul Salam, Safwat Hassaballa, Engy El-Dek, Eslam Sheha

Published in

Langmuir : the ACS journal of surfaces and colloids. Jul 10, 2026. Epub Jul 10, 2026.

Abstract

Magnesium-sulfur (Mg-S) batteries are attractive energy-storage systems but remain limited by sluggish Mg²⁺ transport, interfacial instability, and polysulfide shuttling. Herein, a Li₂CO₃-modified halogen-free electrolyte based on Mg(NO₃)₂ in an acetonitrile/tetraethylene glycol dimethyl ether (ACN/G4) solvent system was combined with a MoS₂/sulfur/graphene nanoplatelet (MoS₂/S/GNP) composite cathode. The modified electrolyte exhibited an ionic conductivity of 1.4 × 10^-4 S cm^-1, representing a ∼17% increase relative to the pristine electrolyte, together with an enhanced Mg²⁺ transference number of 0.867. Symmetric Mg cells showed improved Mg plating/stripping stability and reduced polarization, indicating enhanced Mg/electrolyte interfacial compatibility. The MoS₂/S/GNP cathode provided a conductive framework and catalytic sites for sulfur conversion. However, full-cell studies revealed substantial transport and interfacial limitations during cycling. The charge-transfer resistance increased from 237 to 2516 Ω after electrochemical activation, while the Mg²⁺ diffusion coefficient decreased from 1.00 × 10^-14 to 1.26 × 10^-17 cm² s^-1. Galvanostatic cycling showed rapid capacity fading from ∼ 310 mAh g^-1 in the first cycle to near-zero values after ∼15 cycles, accompanied by Coulombic efficiencies exceeding 100% during the early cycles, indicating significant parasitic reactions and polysulfide shuttling. These results demonstrate that Li₂CO₃ modification influences Mg²⁺ transport and interfacial behavior but is insufficient to overcome the fundamental degradation processes limiting halogen-free Mg-S batteries. The study provides insight into electrolyte-cathode interactions and highlights key challenges for future Mg-S battery development.

PMID:
42430546
Bibliographic data and abstract were imported from PubMed on 11 Jul 2026.

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