Strongly Bonded Selenium/Microporous Carbon Nanofibers Composite as a High-Performance Cathode for Lithium-Selenium Batteries

Although lithium-selenium batteries have attracted significant attention for high-energy-density energy storage systems due to their high volumetric capacity, their implementation has been hampered by the dissolution of polyselenide intermediates into electrolyte. Herein, we report a novel selenium/microporous carbon nanofiber composite as a high-performance cathode for lithium-selenium batteries through binding selenium in microporous carbon nanofibers. Under vacuum and heat treatment, selenium particles are easily transformed into chainlike Se_n molecules that chemically bond with the inner surfaces of microporous carbon nanofibers. This chemical bonding can not only promote robust and intimate contact between selenium and carbonaceous nanofiber matrix but also alleviate the active material dissolution during cycling. Moreover, selenium is homogeneously distributed in the micropores of the highly conductive carbonaceous nanofiber matrix, which is favorable for the fast diffusions of both lithium ions and electrons. As a result, a high reversible capacity of 581 mA h g^-1 in the first cycle at 0.1 C and over 400 mA h g^-1 after 2000 cycles at 1 C with excellent cyclability and high rate performance (over 420 mA h g^-1 at 5 C, 3.39 A g^-1) are achieved with the selenium/microporous carbon nanofibers composite as a cathode for lithium-selenium batteries, performing among the best of current selenium-carbon cathodes. This simple preparation method and strongly coupling hybrid nanostructure can be extended to other selenium-based alloy cathode materials for lithium-selenium batteries.