Resorcinol formaldehyde (RF) polymer derived carbon gels have been widely used as active electrode material in energy storage devices such as supercapacitors and lithium ion batteries due to their tunable surface area by varying drying conditions.1 In addition to the easily tunable surface area, morphology can also be modified by changing the synthesis parameters and methods.2,3 However, RF xerogel derived carbon nanofibers were not studied as anode material for Li-ion battery due to its non-electrospinnability. Recently, RF-based electrospun carbon nanofibers were prepared by blending it with stretchable Polymethyl methacrylate (PMMA).4
In this work, we have synthesized RF xerogel and PMMA blend based carbon nanofibers and used them as potential anode material for lithium ion battery. These RF xerogel derived electrospun carbon nanofibers show larger lithium ion intercalation capacity not only as compared to RF xerogel derived other carbon morphologies such as powder, interconnected carbon nanoparticles but also other carbon nanofibers based electrodes.5,6
Experimental
RF sol was prepared by mixing resorcinol and formaldehyde (4:1 molar ratio) in acetone and HCl. Thus prepared RF sol was blended with templating PMMA polymer (1:2 Vol. ratio). A blend of this solution was used as precursor material for electrospinning. Electrospinning process parameters were tuned to yield long, continuous fibers. Controlled two step pyrolysis of these RF xerogel/PMMA electrospun fibers yielded carbon nanofibers.
Results and discussions:
RF-PMMA blend polymer fibers were electrospun directly on stainless steel wafer used as a substrate cum current collector. Average diameter of RF-PMMA electrospun RF-PMMA nanofibers as shown in Figure 1a was found to be 2.3 µm. These fibers were then pyrolyzed at 900 ⁰C to obtain carbon fibers with average diameter 1.4 µm. X-ray diffraction and Raman spectroscopy studies were done in order to confirm the glassy nature of as-derived carbon nanofibers. These RF-PMMA derived carbon nanofibers based electrode was then used as working electrode in Li (reference electrode) based half-cell. Galvanostatic charge discharge experiments were carried out at 37.2 mA/g current density. An initial reversible capacity of 620 mAh/g (Figure 1b) was observed for these carbon nanofibers which was significantly higher than reported values in literature for RF based powder, RF based graphitic powder and carbon nanoparticles. Further, cyclic stability and coulombic efficiency were found to be excellent. A detailed characterization of these carbon nanofibers and their electrochemical performance at different current densities will be presented during the conference.
References:
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