Improving the Electrochemical Performances of Chalcogen/carbon Composite Cathodes via an In situ Surface Modification

Abstract

Chalcogens such as sulfur (S), selenium (Se), and tellurium (Te), are the promising cathode materials since they have higher gravimetric/volumetric capacities (1672, 679, and 420 mAh g-1 and 3461, 3265, and 2621 mAh cm-3 for S, Se, and Te respectively) than the metal oxide cathodes (e.g., 148 mAh g-1 and 1363 mAh cm-3 for LiCoO2). [1] However, their issolution into an electrolyte and a subsequent performance failure are the main obstacles for their commercialization, hence modifying the surface of chalcogen/C composite (e.g., coating the composite and doping heteroatoms) has been preferred in order to inhibit the dissolution of chalcogens chemically/physically. [2] In this work, we introduce surface-treated chalcogen/carbon cathodes for a high-capacity Li-ion battery using three kinds of in situ surface modification methods; (i) doping a heteroatom on carbon (ii) functionalizing chalcogens on carbon with a mediator (iii) polymerization on chalcogen/C composite. From the studies on the electrochemical behavior (e.g., galvanostat and electrochemical impedance spectroscopy) of the surface-modified electrodes, it is clearly concluded that the modified-surface enhances the ability to trap the soluble intermediates of chalcogen/C cathodes and the kinetics of Li ions simultaneously. References [1] H. Peng et al. Chem. Soc. Rev. (2017) 46, 5237-5288 [2] X. Li et al. Adv. Funct, Mater. (2018) 28, 1801323