Nano-grafit kako anodni materijal za Li-ionske galvanske članke

master's thesis

• Title (english): Nano-graphite anodic material for Li-ion batteries
• Author: Grgur Mihalinec
• Mentor: Zoran Mandić (mentor)
• Committee member: Zoran Mandić (predsjednik povjerenstva)
• Committee member: Marijana Kraljić Roković (član povjerenstva)
• Committee member: Vladimir Dananić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2022-07-01, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

U ovom radu ispitivana su svojstva nano grafita kao anodnog materijala u Li-ionskim galvanskim člancima i mogućnost upotrebe nano grafita kao dodatka siliciju za poboljšanje elektrokemijskih svojstva te stvaranja superiornog anodnog materijala za skladištenje litija. Provedena je fizikalna karakterizacija materijala s ciljem stvaranja korelacije između strukture i svojstava materijala. Karakterizacija materijala TGA analizom pokazala je gubitak mase od svega 0,2 %. FTIR analiza pokazala izostanak vode te malu prisutnost kisikovih skupina što potvrđuje TGA analizu. Analizom veličine čestica DLS tehnikom utvrđena je veličina od 420 nm uske raspodjele prema volumenu te broju čestica. B.E.T analiza pokazala je površinu od 61 m^2/g i veličinu pora 19,2 Å što odgovara području mikropora. Elektrode, na kojima su rađena elektrokemijska ispitivanja, priređene su nanošenjem paste uzoraka nanografita i silicija miješanih s ugljikovim crnilom i polivinilidenfluoridom u raznim omjerima, u obliku tankog filma na bakrenu foliju. Elektrokemijska ispitivanja rađena su metodama cikličke voltametrije, galvanostatskog punjenjenja i pražnjenjenja te elektrokemijske impedancijske spektroskopije. Cikličkom voltameterijom ustanovljeno je kako se dodatkom ugljikovog crnila postiže bolja reverzibilnost interkalacije litija. Nano grafit kao dodatak siliciju je pokazao gubitak odgovarajućih elektrokemijskih svojstva zbog promjene mehanizma interkalacije. Naponski profili pokazuju stabilnost svih materijala tijekom ciklusa punjenja odnosno pražnjenja. Najveći kapacitet postignut je za uzorak nano grafita sa ugljkovim crnilom te iznosi 24,01 mAh g^-1 dok je za silicijev uzorak postignuto 13,59 mAh g^-1. Impedancijskim mjerenjima pokazano je smanjenje unutrašnjeg otpora i otpora prijenosa naboja nakon provedenih ciklusa punjenja i pražnjenja pri čemu je na uzorku nano grafita s ugljikovim crnilom uspješno pokazano stvaranje SEI sloja nakon ciklusa punjenja pražnjenja.

Abstract (english)

In this paper the properties of nano graphite as anode material in Li-ion batteries and the possibility of using nano graphite as an addition to silicon to improve electrochemical properties and to create superior anode materials for lithium storage were investigted. Physical characterization of materials was carried out in order to create a correlation between structure and properties of materials. The characterization of materials by TGA analysis showed a weight loss of only 0,2 %. FTIR analysis showed the lack of water and low presence of oxygen groups, which was confirmed by TGA analysis. The particle size analysis by the DLS technique revealed a size of 420 nm with narrow distribution by volume and number of particles. B.E.T analysis showed a surface area of 61 m^2/g and pore size of 19.2 Å, which belong to the micropore sizes. Electrodes, on which electrochemical tests were conducted, were prepared by applying a paste made from nano graphite and silicon samples mixed with carbon black and polyvinyldenfluoride in various proportions, in the form of a thin film on copper foil. Electrochemical tests were conducted using methods of cyclic voltammetry, galvanostatic charge and dischrage and electrochemical impedance spectroscopy. Cyclic voltamtery showed that addition of the carbon black achieves better reversibility of lithium intercalation. Nano graphite as an addition to silicon showed a loss of certain electrochemical properties due to the change in the intercalation mechanism. Voltage profiles show the stability of all materials during the charging or discharging cycles. The highest capacity of 24.01 mAh g^-1 was achieved for the nano graphite sample with carbon black , while for the silicon sample, 13.59 mAh g^-1 was achieved. Impedance measurements showed a reduction in internal resistance and resistance to charge transfer after completed charging and discharge cycles, whereby a sample of nano graphite with carbon black successfully showed the formation of the SEI layer after a few of the charging and discharging cycles.

• Keywords: nano grafit; silicij; galvanski članak; Li-ionska baterija; anodni materijal
• Keywords (english): nano graphite; silicon; galvanic cell; Li-ion batery; anodic material
• Language: croatian
• URN:NBN: urn:nbn:hr:149:321655
• Study programme: Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry; Course: Advanced materials and technologies; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra primijenjene kemije (magistar/magistra primijenjene kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2023-02-26 15:20:23