Lightweight 3D Structured Carbon Nanofiber Current Collector for Li/S Batteries

Abstract

Light weight carbon nanofibers (CNF) fabricated from polyacrylonitrile (PAN) nanofibers by simple electrospinning method. Electrospinning is one of the simplest and cost-effective techniques to produce carbon nanofibers (CNFs). Furthermore, it is easy to control/manage the diameter, morphology and density/structure of fibers by adjusting spinning parameters like polymer concentration, applied voltage, speed of rotation of drum and distance between nozzle and collector. Prepared CNFs were used as 3D structured current collector for sulfur cathode. The 3D current collector allowed to accommodate a higher amount of sulfur composite which led to a remarkable increase of the electrode capacity from 200 to 500 mAh per 1 gram of the electrode including the mass of the current collector. Varying the electrospinning solution concentration enabled obtaining carbonized nanofibers of uniform structure and controllable diameter from several hundred nanometers to several micrometers. Structural characterization of nanofibers by XRD and Raman spectroscopies revealed that the improvement in ordering graphitic layers of CNFs can be achieved by increasing the heating temperature. PAN nanofibers carbonized at 800 oC were applied as 3D structured current collector for sulfur-based cathode (Figure 1), and electrochemical performance of this cathode was investigated. An initial specific capacity of 1620 mAh g− 1 was achieved with carbonized PAN nanofiber (cPAN) current collector.It exhibited stable cycling over 100 cycles maintaining a reversible capacity of 1104 mAh g−1 at 100th cycle, while the same composite on Al foil delivered only 872 mAh g− 1 . At the same time, 3D structured CNFs with a highly developed surface have a very low areal density of 0.85 mg cm−2 (thickness of ~25 µm), which is lower for almost ten times than commercial Al current collector with the same thickness (7.33 mg cm−2).Acknowlegments:This work was supported by the State Targeted Program #BR05236524 from the Ministry of Education and Science of the Republic of Kazakhstan and by the Faculty-development competitive research grant #110119DF4514 from Nazarbayev University. Figure 1