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Lithium ion batteries contain diverse functional polymeric materials, e.g. binders and separators. Naturally self-assembled wood cellulose can be disintegrated to nanosized particles with a diversity of morphology by top-down processes, adjusting the manufacturing parameters. The nanomaterials can then be reconstructed by bottom-up assembly to structures similar to that of the polymeric materials in lithium ion batteries, capable of replacing their functions and ensuring similar or improved performance. The aim of the thesis is to evaluate the feasibility of wood-based cellulose nanofibers in lithium ion batteries and explore other possible applications. The relationship between the characteristics of nanocellulose, treated by different processes, and their performance as battery components were investigated using electrochemical and in-operando measurements. Development of electrode-integrated cellulose separators was enabled by a non-aqueous drying method. This significantly improved the drying efficiency and can be considered an eco-friendly process without using hazardous chemicals. This study sheds the light on cellulose as a promising separator material, satisfying the industrial needs without trade-off of durability of the material and ion transport properties.Other than lithium ion battery applications, cellulose nanofibrils are introduced as a pH-responsive polymer and a precursor of hydrogel, electrochemically coated on any conductive substrate. Not only hydrogel, this electro-precipitation method also enables to fabricate single or multi-layered composites. The hydrogel and the composites fabricated by this technique can work as functional materials in the diverse electrochemical applications. In summary, the results indicate that using wood-based cellulose as a raw material is beneficial to fabricate the functional materials by eco-friendly manufacturing processes, available for a variety of electrochemical applications, showing excellent performance. Litiumjon-batterier innehåller komponenter, exempelvis bindemedel och separatorer, som består av polymera material. Naturligt bildat cellulosa från trä kan finfördelas till nanometerstora partiklar vars morfologi beror på olika tillverkningsparameterar i sönderdelningsprocessen. Dessa partiklar kan sedan användas för att återskapa nanomaterial med strukturer liknande de i de polymera materialen i litiumjon-batterierna, och som också kan ersätta de senare med likvärdiga eller bättre prestanda. Det huvudsakliga målet med detta arbete är att utvärdera möjligheten att använda nanofibrer av cellulosa från trä i litiumjon-batterier. Cellulosa behandlat på olika sätt har undersökts som material i batterikomponenter, genom elektrokemiska mätningar och in operando tekniker. Separatorer av cellulosa integrerade med elektroder visade sig kunna tillverkas i ett vattenfritt system, vilket avsevärt underlättar dess torkning, i en miljövänlig process utan skadliga kemikalier. Denna studie lyfter fram cellulosa som lovande material för separatorer, som motsvarar industriella behov utan att försämra materialens livslängd och jonledande egenskaper. Utöver applikationen litiumjon-batteri har nanofibrer av cellulosa undersökts som pH-känslig polymer och utgångsmaterial för hydrogeler, vilka har belagts på ledande ytor. Med denna metod kan man också tillverka kompositmaterial innehållande nanopartiklar i enskilda eller i flera skikt. Hydrogeler och kompositer syntetiserade genom denna teknik kan fungera som funktionella material i olika elektrokemiska tillämpningar. Sammanfattningsvis, resultaten indikerar att användning av träbaserad cellulosa som råmaterial är fördelaktigt vid tillverkning av funktionella material genom miljövänliga processer, i olika elektrokemiska användningar där de visar utmärkta prestanda. QC 2020-02-17

TEMPO-oxidized cellulose nanofibrils (TOCN) are pH-responsive biopolymers which undergo sol–gel transition at acidic conditions (pH < 4) due to charge neutralization. Electronically conducting materials can be coated by such gels during aqueous electrolysis, when an electrochemical reaction generates a local pH decrease at the electrode surface. In this work, electro-precipitation of different TOCN gels has been performed on oxygen evolving anodes. We demonstrate that TOCN hydrogels can be electrochemically coated on the surface of any conductive material with even complex 3D shape. Further, not only TOCN but also micro- or nanosized particles containing TOCN composites can be coated on the electrode surface, and coatings containing multiple layers of different composites can be also produced. We demonstrate that this simple and facile electrocoating technique can be subject to various applications, such as coatings making electrodes selective for the hydrogen evolution reaction, as well as a new eco-friendly aqueous-based synthesis of Li-ion battery electrodes. QC 20200217

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. QC 20190326