Browsing by Author "Bakhshi, Adelheid"

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Form-stable, crosslinked cellulose-based paper separators for charge storage applications
(2024-11-01) Selinger, Julian; Islam, M. Tauhidul; Abbas, Qamar; Schaubeder, Jana B.; Zoder, Janis; Bakhshi, Adelheid; Bauer, Wolfgang; Hummel, Michael; Spirk, Stefan
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
In the quest for greener and more efficient energy storage solutions, the exploration and utilization of renewable raw materials is essential. In this context, cellulose-derived separators play a central role in enhancing the performance of green energy storage devices. However, these often exhibit disadvantageous porosity and limited wet strength. Here, we demonstrate a facile approach to tailor thickness (ca. 40 μm), air permeability (0.1–200 cm3 s−1), and mechanical properties of separators by integration of up to 50 wt% microfibrillated cellulose (MFC) into paper sheets. While the MFC enhanced the formation of dense networks, these separators show a poor dimensional stability (folding and creasing) concomitant with a low strength under wet conditions, crucial for assembly and operation. Crosslinking with 1,2,3,4-butanetetracarboxylic acid (BTCA) however, led to an increase in wet strength by up to 6700 % while ensuring dimensional stability. The electrochemical performance, evaluated by impedance spectroscopy and galvanostatic cycling (7500 repetitions) showed comparable results as commercially available glass and polypropylene separators in terms of ion diffusion, charge-discharge rate performance, Ohmic loss and capacitance retention %. The approach demonstrates that disadvantages of paper-based separators in terms of dimensional stability and wet strength can be overcome by a paper technological approach using crosslinking strategies.
Role of intrinsic and extrinsic xylan in softwood kraft pulp fiber networks
(2024-01-01) Schaubeder, Jana B.; Spirk, Stefan; Fliri, Lukas; Orzan, Eliott; Biegler, Veronika; Palasingh, Chonnipa; Selinger, Julian; Bakhshi, Adelheid; Bauer, Wolfgang; Hirn, Ulrich; Nypelö, Tiina
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Xylan is primarily found in the secondary cell wall of plants providing strength and integrity. To take advantage of the reinforcing effect of xylan in papermaking, it is crucial to understand its role in pulp fibers, as it undergoes substantial changes during pulping. However, the contributions of xylan that is added afterwards (extrinsic) and xylan present after pulping (intrinsic) remain largely unexplored. Here, we partially degraded xylan from refined bleached softwood kraft pulp (BSKP) and adsorbed xylan onto BSKP. Enzymatic degradation of 1 % xylan resulted in an open hand sheet structure, while adsorption of 3 % xylan created a denser fiber network. The mechanical properties improved with adsorbed xylan, but decreased more significantly after enzymatic treatment. We propose that the enhancement in mechanical properties by adsorbed extrinsic xylan is due to increased fiber-fiber bonds and sheet density, while the deterioration in mechanical properties of the enzyme treated pulp is caused by the opposite effect. These findings suggest that xylan is decisive for fiber network strength. However, intrinsic xylan is more critical, and the same properties cannot be achieved by readsorbing xylan onto the fibers. Therefore, pulping parameters should be selected to preserve intrinsic xylan within the fibers to maintain paper strength.