| 1. |
- Baker, Darren, et al.
(författare)
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Lignin-based carbon fiber : effect of softwood kraft lignin separation method on multifilament melt-spinning performance and conversion
- 2019
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Ingår i: 20th International symposium on wood, fiber, and pulping chemistry.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A reference lignin separated from an industrial softwood kraft black liquor via an improved LignoBoost process was compared to four other lignins derived from the same liquor. The four lignins were produced by using a) pH-fractionation within the LignoBoost process, b) ultrafiltration of black liquor prior to the LignoBoost process, and c) solvent leaching of the reference lignin using methanol and d) ethanol.Lignin compositional characteristics and thermal properties were compared, and monofilament extrusion used to assess their potential for successful melt spinning at the 24 filament scale. The lignin prepared by ethanol leaching of the reference lignin was found to be most appropriate for potential pilot scale fibre production. This was owing to a high purity, lower comparative glass transition temperature (Tg), and good spinning performance.Thermal pretreatments of the ethanol leached lignin gave a selection of enhanced lignins which were characterized for comparison, and melt spun on pilot multifilament equipment. The enhanced lignins could be continuously melt spun giving filaments with diameters as low as 10 μm and with minimal defects. Conversion of selected filaments provided carbon fibres with a tensile strength of 1259 ± 159 MPa, tensile modulus of 67 ± 3 GPa and diameter of 7.3 ± 0.5 μm.
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| 2. |
- Peuvot, Kevin, et al.
(författare)
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Lignin based electrospun carbon fiber anode for sodium ion batteries
- 2019
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society Inc.. - 0013-4651 .- 1945-7111. ; 166:10, s. A1984-A1990
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Tidskriftsartikel (refereegranskat)abstract
- Sodium ion batteries (SIBs) are emerging as an alternative battery technology to lithium ion batteries because they have the potential of having a similar energy density and the advantage of sodium being more environmentally friendly than lithium. Hard carbon has been shown to be one of the best candidates as anode material for SIBs. However, several challenges need to be solved before commercializing SIBs such as finding cheaper and more efficient precursors to produce hard carbon and increasing the stability of hard carbon electrodes with the electrolyte. Herein, we report a new bio-based free standing electrode made from lignin based electrospun carbon fibers (LCFs) with a high specific capacity of 310 mAh.g−1 and a first coulombic efficiency of 89%. By using high precision coulometry on the LCFs at different carbonization temperatures, it was found that the cycling stability was dependent on the carbonization temperature. The results show that LCFs are a viable and renewable source to be used as anodes in future SIBs. © The Author(s) 2019.
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| 3. |
- Schlee, Philipp, et al.
(författare)
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Free-standing supercapacitors from kraft lignin nanofibers with remarkable volumetric energy density
- 2019
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Ingår i: Chemical Science. - : Royal Society of Chemistry. - 2041-6539. ; 10:10, s. 2980-2988
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Tidskriftsartikel (refereegranskat)abstract
- We have discovered a very simple method to address the challenge associated with the low volumetric energy density of free-standing carbon nanofiber electrodes for supercapacitors by electrospinning Kraft lignin in the presence of an oxidizing salt (NaNO3) and subsequent carbonization in a reducing atmosphere. The presence of the oxidative salt decreases the diameter of the resulting carbon nanofibers doubling their packing density from 0.51 to 1.03 mg cm−2 and hence doubling the volumetric energy density. At the same time, the oxidative NaNO3 salt eletrospun and carbonized together with lignin dissolved in NaOH acts as a template to increase the microporosity, thus contributing to a good gravimetric energy density. By simply adjusting the process parameters (amount of oxidizing/reducing agent), the gravimetric and volumetric energy density of the resulting lignin free-standing carbon nanofiber electrodes can be carefully tailored to fit specific power to energy demands. The areal capacitance increased from 147 mF cm−2 in the absence of NaNO3 to 350 mF cm−2 with NaNO3 translating into a volumetric energy density increase from 949 μW h cm−3 without NaNO3 to 2245 μW h cm−3 with NaNO3. Meanwhile, the gravimetric capacitance also increased from 151 F g−1 without to 192 F g−1 with NaNO3.
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| 4. |
- Schlee, Philipp, et al.
(författare)
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From waste to wealth : From kraft lignin to free-standing supercapacitors
- 2019
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 145, s. 470-480
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Tidskriftsartikel (refereegranskat)abstract
- Pure eucalyptus Kraft lignin derived carbon fiber mats were produced based on a model workflow. It covers the preparation and characterization of the lignin precursor and the carbon materials and its testing in the final application (supercapacitor). Sequential solvent extraction was employed to produce a eucalyptus Kraft lignin precursor which could be electrospun into lignin fibers without any additives. The fiber formation from low molecular weight lignin is assigned to strong intermolecular interactions via hydrogen bonding and π-π-stacking between individual lignin macromolecules which gives rise to association complexes in the electrospinning solution. By stabilization in air, carbonization in N2 and an activation step in CO2, free-standing microporous carbon fiber mats could be produced. These fiber mats possess mainly basic oxygen functional groups which proved to be beneficial when tested as free-standing electrodes in symmetric supercapacitors. Consequently, the CO2-activated fiber mats showed a high specific gravimetric capacitance of 155 F/g at 0.1 A/g, excellent rate capability with 113 F/g at 250 A/g and good capacitance retention of 94% after 6000 cycles when tested in 6 M KOH electrolyte. Therefore, we conclude that lignin itself is a promising precursor to produce microporous, oxygen functionalized carbon fibers serving as free-standing electrodes in aqueous supercapacitors.
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