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Laser Induced Graphene - Implementation and optimization process as supercapacitor electrode material

Daniele Di Giovanni

Laser Induced Graphene - Implementation and optimization process as supercapacitor electrode material.

Rel. Andrea Lamberti. Politecnico di Torino, Corso di laurea magistrale in Nanotechnologies For Icts (Nanotecnologie Per Le Ict), 2018

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The growing energy demand worldwide in pushing researchers for always innovative and better energy storage solutions; among the many and different kind of devices which can collect, store and release energy in form of electrical current, a particular place is occupied by supercapacitors. An electrochemical capacitors or supercapacitor, is a relatively new energy storage device which shows an intermediate behaviour between a capacitor and a battery in terms of energy and power densities. The typical capacitor plate structure is substituted by a complex nanostructured pattern which allows to hugely increase the active surface while keeping low the volume occupied from the electrodes; this new structure accumulates ions which move in an electrolyte, while in a common capacitor just charges accumulate between plate and insulator. The combination of these two factors generates a far superior charge storage, which seems to have the potential to overcome some of the intrinsic limitations of batteries in the energetic field: low power density, problems at high temperatures and relatively low cycle stability.Carbon-based materials are a common choice for electrodes, they have large surface area and a well known production process; ions will accumulate on the electrodes surface in response to a superimposed potential to neutralize it, forming a double layer of opposite charges which gives name to the energy storage mechanism, Electrical Double Layer. Some carbonaceous materials like graphene gained special interest, because of superior mechanical and conductive properties. In particular Laser Induced Graphene is raising among the possible electrode material in the last decade, due an outstanding ease of production and low costs; LIG is not really graphene, it's graphene-like, a few-layer graphene 3D network.The project of this thesis is to carry on a deep analysis of this innovative material, which has potential for flexible electronics, as electrode for a supercapacitor; the analysis will implement a ionic liquid as electrolyte, which grants the device an operating potential window of 3V, three times respect to an aqueous electrolyte supercapacitor.Three different LIG morphologies obtained by varying laser parameters are compared, so that the best one can be subject of further research for optimization processes. The Needle morphology proves to be unquestionably better than Sheet or Porous, both from the mechanical and the electrochemical point of view; the optimization step regarding the line pattern shows a negligible influence of the line design and interline distance overall. Two different strategies were attempted for LIG doping, a Nitric Acid treatment and a conductive polymer coating with PEDOT:PSS; for contact enhancement instead, platinum was sputtered on top of the LIG area to contact with the aluminum current collector. All of these processes did not seem to produce such a major improvement such as to justify any additional step, which adds more complexity to the production system. On the other side, the flexible device not only does work properly under bending stress, but also seems to have a noticeable upgrade in terms of capacity retain as current density increases. Laser Induced Graphene proved to be a bendable, binder free and potentially collector free material to implement for energy storage purposes, with a simple production process, reasons for which LIG is put forward as a promising flexible electronics component.

Relators: Andrea Lamberti
Academic year: 2017/18
Publication type: Electronic
Number of Pages: 79
Corso di laurea: Corso di laurea magistrale in Nanotechnologies For Icts (Nanotecnologie Per Le Ict)
Classe di laurea: New organization > Master science > LM-29 - ELECTRONIC ENGINEERING
Ente in cotutela: Helmholtz institute of Ulm (GERMANIA)
Aziende collaboratrici: UNSPECIFIED
URI: http://webthesis.biblio.polito.it/id/eprint/8232
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