Cobalt sulfide embedded carbon nanofibers as a self-supporting template to improve lithium ion battery performances.

• The CNFs improve the conductivity of the electrode and facilitate electron and lithium ion transport. • The onion carbon layer can be used as a buffer layer to alleviate the volume expansion caused by the charging and discharging process. • The Co 1-x S particles embedded in the CNFs exhibited a high reversible capacity and excellent cycling stability. Metal sulfides are getting increasing attention as cathodic materials in lithium-ion batteries due to their high theoretical capacities. However, the volume expansion and rapid decay of capacity are two main factors during charge and discharge that restricts the applicability of these electrodes. Herein, we reported a strategy to obtain cobalt sulfide (Co 1-x S)-carbon nanofibers (CNFs) using an electrospinning technique combined with a solvothermal method to increase the capacity of cobalt sulfide and alleviate the volume expansion. Results showed that the as-obtained flexible self-supporting Co 1-x S-CNFs electrode promotes the electron transfer and mechanical stability. Moreover, it was shown that Co 1-x S was embedded in CNFs, which improved the electrical conductivity of the composite and alleviated the volume expansion caused by charging and discharging. The synergistic effect from the enhanced electrical conductivity of CNFs and high capacity of the Co 1-x S exhibited a high specific discharge capacity (620 mAh g−1 at 100 mA g−1) and good cycling stability (retaining capacity of 252 mAh g−1 after 500 cycles at 2000 mA g−1). This work demonstrated the efficiency of cobalt metal catalysis and the simple method of vulcanization design in the fabrication of high-performance lithium ions batteries. Image, graphical abstract [ABSTRACT FROM AUTHOR]