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Nanocellulose: Energy Applications and Self-Assembly
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Technologies based on renewable materials are required to decrease the environmental cost and promote the development of a sustainable society. In this regard, nanocellulose extracted from wood finds many applications thanks to its intrinsic mechanical and chemical properties as well as the versatility in its manufacturing processes. In this thesis, I present the results of the investigations on carboxylated cellulose nanofibres (CNF) as ionic conductive membranes and electrode component in fuel cells and lithium ion batteries. Moreover, I also show the results of the assembly of CNF suspension and cellulose nanocrystals (CNC) - lepidocrocite nanorods (LpN) hybrids.

The fuel cell performance of CNF-based proton conductive membranes was evaluated as a function of intrinsic material parameters such as membrane thickness and surface charge density as well as extrinsic parameters such as the relative humidity (RH). It was found that the proton conductivity is about 2 mS cm-1 at 30 °C between 65 and 95 % RH. At the same time, the water uptake of the membrane was measured and correlated with the structural evolution of the membrane using small angle X-ray scattering.

The performance of the CNF-based separator in lithium ion batteries was investigated as a function of membrane porosity and protonation of the functional groups. The Li-ion battery assembled with the protonated separators showed stable and good rate performance.

The CNF was also tested as binder in lithium ion battery, showing that the morphology and mechanical properties of the cathode depend on the nanofibre surface charge and degree of defibrillation. In particular, high surface charge and medium degree of defibrillation give the best electrochemical performance.

Pyrolysed CNF (cCNF) improved the electrochemical performance of silicon nanoparticles-based anode thanks to the carbon network derived from the nanofibres. Si-cCNF has a capacity retention of 72.2 % after 500 cycles at 1 C and better performance rate than the pristine silicon nanoparticles.

Regarding the assembly of nanocellulose, the nematic order of CNF suspension at different nanofibre concentrations (0.5 – 4.9 wt%) was studied by small angle X-ray scattering, polarized optical microscopy and rheological measurements. The order parameter reaches a maximum value of 0.8 depending on the CNF concentration. Small angle neutron scattering with contrast matching experiments reveals that the natural alignment of CNC and LpN can be switched using a combination of magnetic fields of up to 6.8 T and varying the amount of LpN incorporated in the CNC.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University , 2019. , p. 82
Keywords [en]
nanocellulose, self-assembly, fuel cell, lithium ion battery
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
URN: urn:nbn:se:su:diva-171459ISBN: 978-91-7797-815-2 (print)ISBN: 978-91-7797-816-9 (electronic)OAI: oai:DiVA.org:su-171459DiVA, id: diva2:1341513
Public defence
2019-09-20, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 6: Manuscript.

Available from: 2019-08-28 Created: 2019-08-08 Last updated: 2019-08-20Bibliographically approved
List of papers
1. Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells
Open this publication in new window or tab >>Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells
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(English)Manuscript (preprint) (Other academic)
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-171412 (URN)
Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2019-08-19Bibliographically approved
2. Lithium Ion Battery Separators Based On Carboxylated Cellulose Nanofibers From Wood
Open this publication in new window or tab >>Lithium Ion Battery Separators Based On Carboxylated Cellulose Nanofibers From Wood
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2019 (English)In: Acs Applied Energy Materials, ISSN 2574-0962, Vol. 2, no 2, p. 1241-1250Article in journal (Refereed) Published
Abstract [en]

Carboxylated cellulose nanofibers, prepared by TEMPO-mediated oxidation (TOCN), were processed into asymmetric mesoporous membranes using a facile paper-making approach and investigated as lithium ion battery separators. Membranes made of TOCN with sodium carboxylate groups (TOCN-COO-Na+) showed capacity fading after a few cycles of charging and discharging. On the other hand, its protonated counterpart (TOCN-COOH) showed highly improved electrochemical and cycling stability, displaying 94.5% of discharge capacity maintained after 100 cycles at 1 C rate of charging and discharging. The asymmetric surface porosity of the membranes must be considered when assembling a battery cell as it influences the rate capabilities of the battery. The wood-based TOCN-membranes have a good potential as an ecofriendly alternative to conventional fossil fuel-derived separators without adverse side effects.

Keywords
cellulose, Li-ion batteries, separator, TEMPO-oxidized cellulose, protonation
National Category
Chemical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-167548 (URN)10.1021/acsaem.8b01797 (DOI)000459948900036 ()
Available from: 2019-04-15 Created: 2019-04-15 Last updated: 2019-08-19Bibliographically approved
3. Effects of Different Manufacturing Processes on TEMPO-Oxidized Carboxylated Cellulose Nanofiber Performance as Binder for Flexible Lithium-Ion Batteries
Open this publication in new window or tab >>Effects of Different Manufacturing Processes on TEMPO-Oxidized Carboxylated Cellulose Nanofiber Performance as Binder for Flexible Lithium-Ion Batteries
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2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 43, p. 37712-37720Article in journal (Refereed) Published
Abstract [en]

Carboxylated cellulose nanofibers (CNF) prepared using the TEMPO-route are good binders of electrode components in flexible lithium-ion batteries (LIB). However, the different parameters employed for the defibrillation of CNF such as charge density and degree of homogenization affect its properties when used as binder. This work presents a systematic study of CNF prepared with different surface charge densities and varying degrees of homogenization and their performance as binder for flexible LiFePO4 electrodes. The results show that the CNF with high charge density had shorter fiber lengths compared with those of CNF with low charge density, as observed with atomic force microscopy. Also, CNF processed with a large number of passes in the homogenizer showed a better fiber dispersibility, as observed from rheological measurements. The electrodes fabricated with highly charged CNF exhibited the best mechanical and electrochemical properties. The CNF at the highest charge density (ISSO mu mol g(-1)) and lowest degree of homogenization (3 + 3 passes in the homogenizer) achieved the overall best performance, including a high Young's modulus of approximately 311 MPa and a good rate capability with a stable specific capacity of 116 mAh g(-1) even up to 1 C. This work allows a better understanding of the influence of the processing parameters of CNF on their performance as binder for flexible electrodes. The results also contribute to the understanding of the optimal processing parameters of CNF to fabricate other materials, e.g., membranes or separators.

Keywords
CNF, binder, charge density, degree of homogenization, flexible Li-ion batteries
National Category
Chemical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-150011 (URN)10.1021/acsami.7b10307 (DOI)000414506600023 ()28972727 (PubMedID)
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2019-08-19Bibliographically approved
4. Extensively interconnected silicon nanoparticles via carbon network derived from ultrathin cellulose nanofibers as high performance lithium ion battery anodes
Open this publication in new window or tab >>Extensively interconnected silicon nanoparticles via carbon network derived from ultrathin cellulose nanofibers as high performance lithium ion battery anodes
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2017 (English)In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 118, p. 8-17Article in journal (Refereed) Published
Abstract [en]

Silicon is a good alternative to conventional graphite anode but it has bad cycling and rate performance. To overcome these severe problems, extensively interconnected silicon nanoparticles using carbon network derived from ultrathin cellulose nanofibers were synthesized. Ultrathin cellulose nanofibers, an abundant and sustainable material, entangle each silicon nanoparticle and become extensively interconnected carbon network after pyrolysis. This wide range interconnection provides an efficient electron path by decreasing the likelihood that electrons experience contact resistivity and also suppresses the volume expansion of silicon during lithiation. In addition, Ultrathin cellulose nanofibers are carboxylated and therefore adhesive to silicon nanoparticles through hydrogen bonding. This property makes ultrathin cellulose the perfect carbon source when making silicon composites. As a consequence, it exhibits 808 mAh g(-1) of the reversible capacity after 500 cycles at high current density of 2 A g(-1) with a coulombic efficiency of 99.8%. Even at high current density of 8 A g(-1), it shows a high reversible discharge capacity of 464 mAh g(-1). Moreover, extensively interconnected carbon network prevents the formation of a brittle electrode with a water-based binder. Therefore, this remarkable material has a huge potential for LIBs applications.

Keywords
Anode, Cellulose nanofiber, Li ion battery, Silicon-carbon nanocomposite
National Category
Chemical Sciences
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-144773 (URN)10.1016/j.carbon.2017.03.028 (DOI)000401120800002 ()
Available from: 2017-07-17 Created: 2017-07-17 Last updated: 2019-08-19Bibliographically approved
5. Inducing nematic ordering of cellulose nanofibers using osmotic dehydration
Open this publication in new window or tab >>Inducing nematic ordering of cellulose nanofibers using osmotic dehydration
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2018 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 48, p. 23157-23163Article in journal (Refereed) Published
Abstract [en]

The formation of nematically-ordered cellulose nanofiber (CNF) suspensions with an order parameter f(max) approximate to 0.8 is studied by polarized optical microscopy, small-angle X-ray scattering (SAXS), and rheological measurements as a function of CNF concentration. The wide range of CNF concentrations, from 0.5 wt% to 4.9 wt%, is obtained using osmotic dehydration. The rheological measurements show a strong entangled network over all the concentration range whereas SAXS measurements indicate that at concentrations >1.05 wt% the CNF suspension crosses an isotropic-anisotropic transition that is accompanied by a dramatic increase of the optical birefringence. The resulting nanostructures are modelled as mass fractal structures that converge into co-existing nematically-ordered regions and network-like regions where the correlation distances decrease with concentration. The use of rapid, upscalable osmotic dehydration is an effective method to increase the concentration of CNF suspensions while partly circumventing the gel/glass formation. The facile formation of highly ordered fibers can result in materials with interesting macroscopic properties.

National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-163525 (URN)10.1039/c8nr08194h (DOI)000453248100046 ()30515496 (PubMedID)
Available from: 2019-01-07 Created: 2019-01-07 Last updated: 2019-08-19Bibliographically approved
6. Tuning the magnetic alignment of cellulose nanocrystals from perpendicular to parallel using lepidocrocite nanoparticles
Open this publication in new window or tab >>Tuning the magnetic alignment of cellulose nanocrystals from perpendicular to parallel using lepidocrocite nanoparticles
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(English)Manuscript (preprint) (Other academic)
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-171458 (URN)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-08-19Bibliographically approved

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