Surface-treated Selenium/carbon Cathode for Rate and Cyclic Performance of High-capacity Li-ion Battery

Abstract

Sulfur have garnered considerable attention as a promising cathode material for next-generation lithium ion batteries due to its high theoretical capacity (1672 mAh g-1 and ＆shy;3461 mAh cm-3 ) and earth-abundancy [1]. Along with sulfur, selenium in the same chalcogen group have also been considered as an alternative candidate for cathode materials as it exhibits higher conductivity compared to the sulfur (10-5 S cm-1 vs. 5 ＆times; 10＆minus;30 S cm＆minus;3) as well as high theoretical capacity (679 mAh g-1 and 3265 mAh cm-3 ). Despite these advantages, the dissolution of intermediate products into an electrolyte during cycles remain challenge for their future commercialization. Therefore, chalcogen materials have been composited and/or coated with carbon-based materials to enhance the cyclic performance and reaction kinetics. Even though these various solutions, their practical applications have been hampered since most of them require multi-step procedures and, thereby is cost-expensive. Herein, we present a facile and costeffective in-situ polymerization method to enhance electrochemical performances of chalcogenbased cathode material. Monomers of conductive polymer are electrochemically polymerized during pre-charging step to form conductive network composed of chalcogens, polymers, and carbons. This conductive network facilitates lithium ion diffusion, resulting in 2 C-rate retains 56% of that at C/10 (Untreated one is only 0.06 %). Furthermore, the high capacity retention (78% after 200 cycles) is assured since the dissolved particles are anchored by the polymer/carbon network. In stark contrast, untreated electrode resulted in at most 30% capacity retention. It is clear that the in-situ electrochemical polymerization is an effective method to impede the dissolution of intermediate products and hence increase the cyclic stability. References [1] Liu, T. et al. Confined selenium within metal-organic frameworks derived porous carbon microcubes as cathode for rechargeable lithium＆ndash;selenium batteries. J. Power Sources 341, 53＆ndash;59 (2017).