Abstract
Freestanding yet flexible membranes of MnO/carbon nanofibers are successfully fabricated through incorporating MnO2 nanowires into polymer solution by a facile electrospinning technique. During the stabilization and carbonization processes of the as-spun membranes, MnO2 nanowires are transformed to MnO nanoparticles coincided with a conversion of the polymer from an amorphous state to a graphitic structure of carbon nanofibers. The hybrids consist of isolated MnO nanoparticles beading in the porous carbon and demonstrate superior performance when being used as a binder-free anode for lithium-ion batteries. With an optimized amount of MnO (34.6 wt%), the anode exhibits a reversible capacity of as high as 987.3 mAh g−1 after 150 discharge/charge cycles at 0.1 A g−1, a good rate capability (406.1 mAh g−1 at 3 A g−1) and an excellent cycling performance (655 mAh g−1 over 280 cycles at 0.5 A g−1). Furthermore, the hybrid anode maintains a good electrochemical performance at bending state as a flexible electrode.
Highlights
Flexible lithium-ion batteries (LIBs) hold great promise for the generation energy sources of future electronic devices
Different from our previous work[37], in which a rod-like hierarchical core-corona nanostructure was prepared by a hydrothermal method, here we selected MnO2 NWs as Mn source, which are more likely uniaxially aligned along the carbon nanofibers (CNFs)
The peaks at 12.8°, 18.1°, 28.8° and 37.5° can be clearly seen from the as-spun MnO2/PAN nanofiber (MnP) membrane, which are attributed to the diffractions from (110), (200), (310) and (211) faces of α -MnO238,39, respectively, suggesting well-maintained crystal nanostructures of MnO2 NWs in MnP membrane
Summary
TEM image (Fig. 4(b)) further confirms the existence of the tubular pores inside nanofibers The formation of such a porous structure could be attributed to Figure 3. The high resolution TEM image (Fig. 4(c)) shows clear lattice fringes for graphitic structure and Fast Fourier Transform (FFT) of the red square area demonstrates (002) of carbon and (220), (111) diffraction points of MnO, further indicating that the obtained product is dominant by MnO particles. In our work, the resultant MnO NPs embedded in porous CNFs might be related to the strong synergistic effects between the morphological evolution of Mn-oxides and the structural transformation of PAN from an amorphous to graphitic carbons. The initial cyclic voltammograms (CV) curve of MnC electrode (Fig. 5(a)) shows an irreversible reduction peak at around 0.72 V in the first cycle, corresponding to the irreversible reduction of electrolyte and the formation of a solid electrolyte interphase (SEI)
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