Ni-Foil etching to improve the adhesion of carbon electrodes and enhance

• Autor(a) principal: Tomé, Mariana Pereira
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/123157
• topic: energy storage; supercapacitors; current collectors; nickel foil; adhesion; etching; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

A lot of research is being focused on the field of energy storage and conversion nowadays. It is very important to provide energy conversion and good storage systems for many applications. Batteries and supercapacitors are thus receiving a lot of attention. The past research on supercapacitors allowed them to be widely seen as an alternative for high-power applications to replace batteries in technologies as important as UPS, car regenerative breaking, and engine starting. Literature highlights a vast range of potential materials but scarcely addresses the scaling-up manufacturing process of supercapacitors. A critical step during manufacturing is substrate pre-treatments, required for adequate adhesion of the active material on the conductive substrate, that tends to be smooth with low roughness. In this thesis, etching techniques on nickel foil substrate have been tested to increase the surface roughness and improve the adhesion. For this purpose, different etching techniques were studied. Chemical etching solutions were considered, obtaining the best performing one and optimizing the etching parameters for the studied etchant solutions. Complementary to this, techniques like screen-printing and calendaring were also performed and tested with the chemical etching. Also, dry etching was studied aiming to optimize its parameters. The performance of these etched electrodes was evaluated through techniques as diverse as SEM, AFM, contact angle, cross-cut test, and electrochemical analysis. The best performance was achieved with the acidic solution FeCl3 at 15% in DI water, reducing the interfacial resistance from 0.021Ω in a clean nickel foil substrate to 0.008Ω in an etched sample, making it 2.6 times smaller and thus proving that this etching increased the adhesion. Furthermore, there was also a 51% increase in capacitance, from 16.5F to 25F in the etched sample over 2000 cycles. Overall, this work allowed to obtain the best etchant to increase the roughness of the nickel foil. This roughness increase proved to enhance the supercapacitor performance, diminishing the ESR and increasing the capacitance