Defence of doctoral thesis: Hyeyun Kim – Wood-Based Nanocellulose In Lithium Ion Batteries and Electrochemical Coatings

Abstract

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.