Modulated Dehydration for Enhanced Anodic Performance of Bacterial Cellulose derived Carbon Nanofibers

Abstract

Carbon nanofibers (CNF) have shown to improve electrochemical performance when used as anode materials in Lithium-ion batteries. Bacterial cellulose (BC), which is naturally produced as a hydrogel, yields CNF upon drying followed by pyrolysis. The BC derived CNF, primarily involving freeze-drying, have been successfully tested as a potential anode material. However, in order to enhance the anodic performance, we need to tune the physiochemical properties of BC. This work is a first of its kind attempt to systematically study the effect of dehydration conditions (namely, oven and freeze drying) of bacterial cellulose hydrogel (produced using two bacterial strains) on the microstructural properties and electrochemical performance of as-derived CNF. Finally, we demonstrate the use of oven-dried bacterial cellulose as a sustainable and scalable precursor for CNF with a reversible capacity of 440 mAhg À 1 at 0.2 C-rate with ∼ 99% coulombic efficiency after 100 continuous charge/discharge cycles.

Nitrogen and Oxygen Codoped Carbon Anode Fabricated Facilely from Polyaniline Coated Cellulose Nanocrystals for High-Performance Li-Ion Batteries

“…The structural variations of c-CNC, c-PANi, and c-CNC/PANi were investigated by Raman spectroscopy as presented in Figure a. It clearly showed that all samples exhibited three remarkable peaks located at around 1350, 1580, and 2820 cm –1 corresponding to D, G, and 2D bands, respectively. ,,,,− ,− As is known, the “G-band” is ascribed to sp 2 -hybridized carbon which can be used to explain the degree of graphitization, while the “D-band” in the lower frequency region is associated with structural defects and partially disordered carbonaceous structures. The “2D band” should be attributed to the characteristic features of few-layered graphene. ,,,,, It is generally accepted that the relative intensity ratio of the D to G bands ( I D / I G ) is related to the amount of defects in the carbon structure.…”

“…It has been reported that the larger intergraphene-layer spacing was beneficial for the intercalation and deintercalation of Li ions in the carbon anode. 19,40,41 Raman spectroscopy is a sensitive technique to characterize the defects and the ordered and disordered structures in carbon systems. The structural variations of c-CNC, c-PANi, and c-CNC/PANi were investigated by Raman spectroscopy as presented in Figure 3a.…”

“…The "2D band" should be attributed to the characteristic features of fewlayered graphene. 27,35,37,40,42,44 It is generally accepted that the relative intensity ratio of the D to G bands (I D /I G ) is related to the amount of defects in the carbon structure. The I D /I G ratio for c-CNC was approximately 0.86, while the ratios for c-CNC/PANi and c-PANi were approximately 0.94 and 0.96, respectively.…”

“…According to the Bragg’s law, the intergraphene-layer spacings of c-CNC/PANi prepared at the carbonization temperature of 600, 700, and 800 °C were calculated to be 0.400 nm, 0.375 nm, and 0.369 nm, respectively, which were much larger than that of graphite (0.334 nm). It has been reported that the larger intergraphene-layer spacing was beneficial for the intercalation and deintercalation of Li ions in the carbon anode. ,, …”

“…The EIS spectra of these three anodes, as the Nyquist plots, were presented in Figure S6a. As can be seen, the Nyquist plots of all electrodes exhibited a typical depressed semicircle in the high- or medium-frequency region along with an inclined line in the low-frequency region. ,,, The equivalent circuit diagram was used to fit the Nyquist plots (inset of Figure S6a), consisting of resistors and constant phase elements in series and parallel combinations, ,,, and the fitting values of the corresponding parameters ( R s is the intercept of the high-frequency signal with the Z′ axis, representing the analogous ohmic resistance; R ct is the diameter of the semicircle in the medium-frequency region, representing the interfacial charge transfer resistance; D is the Li-ion diffusion coefficient calculated from the inclined line in the low-frequency region) ,, are summarized in Table S1. It can be seen that the c-CNC/PANi electrode presented the smallest R s and R ct of around 3.7 and 76.3 Ω, respectively, and the largest D of around 1.5 × 10 –8 cm 2 s –1 .…”