Cobalt phthalocyanine derived bifunctional carbon decorated CoSe with enhanced lithium storage capability

Abstract

Transition-metal chalcogenides (TMCs) have attracted much attention as their good electrical conductivity and high lithium storage capacity. In this work, a simple and scalable approach was employed to synthesize CoSe nanoparticles confined in bifunctional N-doped carbon framework/carbon layer (CoSe/NC/C). Specifically, pyrolysis of cobalt phthalocyanine (CoPc)/Selenium mixtures was accompanied by Ethanol Steam Reforming (ESR) simultaneously, which could bring in double carbon network and restrict the growth of CoSe grains effectively to achieve more stable structure and fast ion/electron transfer within CoSe electrode. As a result, CoSe/NC/C composite delivers a superior discharge capacity of 531 mA h g-1 after 400 cycles at 1 A g-1 at room temperature and a remarkable cycling stability (458 mA h g-1 after 100 cycles at 1 A g-1) at elevated temperature (55 ℃). This excellent electrochemical performance may be attributed to the following factors. (a) The bifunctional carbon architecture can not only endow the composites with superior conductivity and enhanced structure stability, but also facilitate the uniform distribution of nano-sized CoSe. (b) The effective catalytic activity is inspired by the synergistic effect between CoSe nanoparticles and bifunctional carbon, which is supposed to contribute significant capacity and manifest distinct pseudocapacitive behavior, especially at high current density.