PVD yöntemi ile silisyum matrisli karbon nanotüp takviyeli nano kompozit elektrotların geliştirilmesi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Anahtar kelimeler: PVD, silisyum, karbon nano tüp, nano kompozit anode, lityum-iyon pil.Taşınabilir elektronik cihazların yaygınlaşması ve elektrikli araçların kullanımının, dünyadaki karbon dioksit salınımının azaltılması adına ihtiyaç haline gelmesi nedeniyle verimli ve yüksek enerji yoğunluklu şarj edilebilir pillere olan gereksinim artmaktadır. Lityum iyon piller bu amaç için halen kullanılmakta olan en gözde seçenek olmakla gelişmeler açısından da en çok gelecek vaat eden pil sistemleridir.Bu tez çalışmasında lityum iyon pillerde kullanılmak üzere silisyum esaslı kompozit anotlar üretilmiştir. Silisyum doğru akım sıçratma tekniği kullanılarak paslanmaz çelik altlık ve karbon nano tüp kâğıtlar üzerine sıçratılmış, ince film ve nano kompozit anotlar elde edilmiştir. Üretilen kompozitlere taramalı elektron miskroskobisi ve X ışınları difraksiyon teknikleri ile analizler yapılmıştır.Kompozit anot mimarisini elde edebilmek üzere karbon nanotüp kâğıtlar vakum filtrasyon tekniği kullanılarak üretilmiştir. Vakum filtrasyon tekniğinden önce karbon nano tüpler saflaştırılmış daha sonra da çeşitli kimyasal yöntemlerle fonksiyonelleştirme işlemi uygulanmıştır. Fonksiyonelleştirilen karbon nano tüplere termal analiz ve fourier dönüşümlü kızılötesi spektroskopi analizi uygulanmıştır. Kâğıtların morfolojileri alan emisyonlu taramalı elektron mikroskobu ile incelenmiştir.Elektrokimyasal testleri yapmak üzere CR2016 tipi piller saf argon doldurulmuş glove box içerisinde üretilmiştir. Çalışma elektrotu olarak üretilen kompozitler kullanılırken referans elektrot olarak yüksek saflıkta lityum folyolar kullanılmıştır. Üretilen piller çevrim ömürlerinin belirlenmesi amacı ile sabit akım yoğunluğunda elektrokimyasal çevrim testlerine tabi tutulmuşlardır. Bunun yanında elektrokimyasal empedans analizi ve çevrimsel voltametri teknikleri ile üretilen anotların elektrokimyasal performansları test edilmiştir.Key Words: PVD, silicon, carbon nanotube, nano composite anode, lithium-ion battery.Due to widespread usage of portable electronic devices and growing necessity of electrical vehicles in order to decrease carbon dioxide emission, the need of high energy density batteries is increasing. Lithium ion batteries are the most popular choice used for this purpose and most promising battery systems in terms of developments in the field of batteries.In this thesis work silicon based composite anodes were produced for lithium ion batteries. Silicon was sputtered via DC magnetron sputtering technique onto stainless steel substrates and carbon nanotube papers to obtain thin film and composite anodes. Obtained electrodes were analyzed via X-ray diffraction technique and scanning electron microscope.Carbon nanotube papers were produced with vacuum filtration technique to obtain composite electrode architecture. Before vacuum filtration process carbon nanotubes were purified and then functionalized with different chemical agents. Thermal analysis and Fourier transform infrared spectroscopy was applied to functionalized carbon nanotubes. Field emission scanning electron microscopy analysis carried out to understand morphology of carbon nanotube papers.CR2016 type coin cells were assembled for electrochemical tests in an argon filled glove box. Composite and thin film electrodes were chosen as working electrode while high purity lithium foils were chosen as reference electrode. To determine the cycle lives, batteries were subjected to galvanostatic charge/discharge tests at constant current density. Besides electrochemical impedance spectroscopy and cyclic voltammetry techniques were used for further electrochemical performance analysis

Cyclic Performance Tests of Si/MWCNT Composite Lithium Ion Battery Anodes at Different Temperatures

In this study silicon-multi walled carbon nanotube (Si-MWCNT) lithium ion battery anodes were produced and their electrochemical galvanostatic charge/discharge tests were conducted at various (25 degrees C, 35 degrees C, 50 degrees C) temperatures to determine the cyclic behaviors of anode at different temperatures. Anodes were produced via vacuum filtration and DC magnetron sputtering technique. Silicon was sputtered onto buckypapers to form composite structure of anodes. SEM analysis was conducted to determine morphology of buckypapers and Si-MWCNT composite anodes. Structural and phase analyses were conducted via X-ray diffraction and Raman Spectroscopy technique. CR2016 coin cells were assembled for electrochemical tests. Cyclic voltammetry test were carried out to determine the reversibility of reactions between anodes and reference electrode between 0.01-2.0 V potential window. Galvanostatic charge/discharge tests were performed to determine cycle performance of anodes at different temperatures

Towards high cycle stability yolk-shell structured silicon/rGO/MWCNT hybrid composites for Li-ion battery negative electrodes

Owing to the highest known theoretical specific capacity of 4200 mAhg(-1), low lithiation voltage characteristics and natural abundance, silicon is considered as the most promising negative electrode material for lithium ion batteries which has the potential to replace graphite. Although having striking features, massive volumetric expansions leading to mechanical pulverization and unstable solid electrolyte interphase hinder silicon to be practically exploited as negative electrode material. To address this challenge we design a binder-free and freestanding composite electrode structure which contains embedded silicon yolk-shell particles between graphene/multi walled carbon nanotube skeleton as anode for lithium ion batteries. Electrochemical charge/discharge test results showed that composite anodes exhibited 951 m Ahg(-1) of gravimetric capacity after 500 cycles. This remarkable performance could be ascribed to the complementary effect of yolk-shell particles and conductive structure of graphene/carbon nanotube skeleton

Li-iyon piller için kalay esaslı grafen kompozit anotun yapısal ve elektrokimyasal karakterizasyonu

Bu çalışmada, ultrasonik prosesör destekli solüsyon esaslı bir kimyasal yöntem Li-iyon piller için kalay esaslı grafen kompozit elektrotların sentezi için geliştirilmiştir. Hummers metodu ile pulcuk grafitten üretilen grafen tabakaları üzerine SnCl2.2H2O başlangıç malzemesi kullanılarak SnO2 nanotozları büyütülmüştür. Kompozit elektrotlar taramalı elektron mikroskobu (SEM), X-ışını difraktometresi ve termal analiz teknikleri ile karakterize edilmiştir. Üretilen kompozit elektrotlar CR2016 Li-iyon düğme tipi hücreye anot olarak bağlanmış ve şarj-deşarj çevrim testleri ve çevrimli voltametre analizleri yapılmıştır. Yüksek performanslı kalay esaslı elektrot malzemesinin hacim genleşmesi problemini aşmak için malzemenin grafen tabakaları üzerine büyütülmesi ile uzun çevrim ömrü elde edilmiştir. Tek adımda üretilen SnO2-grafen nanokompozitinden hazırlanan elektrottan 100 çevrim sonunda 385 mAhg-1 değerinde spesifik kapasite elde edilmiştir

Nanostructured ATO Anodes Produced by RF Magnetron Sputtering for Li-Ion Batteries

In this study, the reversible capacities, as well as the cycling behavior, of crystalline antimony-doped tin oxide (ATO) films have been investigated. ATO films were deposited on Cr-coated stainless steel substrates by the RF magnetron sputtering technique, with antimony-doped tin oxide (SnO2:Sb) target in a mixed oxygen/argon gas environment. The ATO films were deposited for 1.0 h in a mixture of Ar and O-2 environment with O-2/Ar ratio of 10/90, at sputtering power of 75 NW, 100 W and 125 W RF. ATO films were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). The electrochemical properties of ATO anodes were studied using 2016-type coin cells assembled in an argon-filled glove box

Graphene supported heterogeneous catalysts for Li-O-2 batteries

In this study production and characterization of free-standing and flexible (i) graphene, (ii) alpha-MnO2/graphene, (iii) Pt/graphene (iv) alpha-MnO2/Pt/graphene composite cathodes for Li-air batteries were reported. Graphene supported heterogeneous catalysts were produced by a facile method. In order to prevent aggregation of graphene sheets and increase not only interlayer distance but also surface area, a trace amount multi-wall carbon nano tube (MWCNT) was introduced to the composite structure. The obtained composite catalysts were characterized by SEM, X-ray diffraction, N-2 adsorption-desorption analyze and Raman spectroscopy. The electrochemical characterization tests including galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurement of catalyst were carried out by using an ECC-Air test cell. These highly active graphene supported heterogeneous composite catalysts provide competitive properties relative to other catalyst materials for Li-air batteries. (C) 2016 Elsevier B.V. All rights reserved

Structural and electrochemical characterization of tin based graphene composite anode for li-ion batteries

In this study, ultrasound assisted solution based chemical synthesis method has been developed to synthesize tin based graphene composite electrodes for Li-ion batteries. SnO2 was grown by using SnCl2.2H(2)O precursor material on graphene layers was produced Hummers method by using flake graphite. The composite electrodes were characterized with scanning electron microscopy (SEM), X-ray diffractometer and thermal analysis methods. The produced composite electrodes were connected to CR2016 button cells as anode and carried out charge-discharge and cyclic voltammeter tests. Long cycle life was achieved by growing tin based electrode materials with high performance on graphene layers to overcome volume expansion problem. The electrode prepared one-step synthesized SnO2-graphene nanocomposite has shown 385 mAhg(-1) specific capacity value after 100 cycles

Sn/SnO2/Mwcnt composite anode and electrochemical impedance spectroscopy studies for Li-ion batteries

Tin/tinoxide/multi-walled carbon nanotube (Sn/SnO2/MWCNT) core-shell structure nanocomposite anode is produced by thermal evaporation and subsequent plasma oxidation with using MWCNT buckypaper. Metallic tin is evaporated onto free-standing and flexible MWCNT buckypaper having controlled porosity and subsequent RF plasma oxidized in Ar:O-2(1:1) gas mixture. X-ray diffraction and scanning electron microscopy are used to determine the structure and morphology of the obtained nanocomposite. The electrochemical characteristics of the nanocomposite anode are examined by using electrochemical impedance spectroscopy and galvanostatic charge-discharge experiments. Family of Nyquist plots during first discharge process are obtained and studied at different voltage values

The Effect of Oxidants on the Formation of Multi-Walled Carbon Nanotube Buckypaper

In the present study, we report the systematic investigation of the effect of chemical oxidation on the structure of multi-walled carbon nanotubes (MWCNTs) and multi-walled carbon nanotubes buckypaper. The chemical oxidation of multi-walled carbon nanotubes was performed via using three types of chemical solutions: nitric acid, sulfuric acid/nitric acid (3/1) and ammonium hydroxide/hydrogen peroxide (1/1). The surfaces of the multi-walled carbon nanotubes were modified by forming Carboxyl and other functional groups. Flexible multi-walled carbon nanotubes buckypapers were then produced by vacuum filtration techniques from functionalized multi-walled carbon nanotubes. The characteristic properties of multi-walled carbon nanotubes specimens were investigated via Raman, and Fourier Transform Infrared Spectroscopies. The thermal properties and morphology of multiwalled carbon nanotubes were also studied by Thermogravimetric Analysis and Field Emission Scanning Electron Microscopy techniques

Electrochemical characterization of silicon/graphene/MWCNT hybrid lithium-ion battery anodes produced via RF magnetron sputtering

In this study it was aimed to enhance cycling performance of silicon lithium ion battery anodes via producing flexible Silicon/Graphene/MWCNT composite structures. The volumetric expansions, which are the primary obstacle that hinders the practical usage of silicon anodes, were tried to suppress using flexible graphene/MWCNT paper substrates. Moreover to achieve lightweight and high electrical conductive anodes, the advantage of graphene was aimed to be exploited. Silicon/graphene/MWCNT flexible composite anodes were produced via radio frequency (RF) magnetron sputtering technique. Graphene/MWCNT papers were produced with vacuum filtration technique as substrate for sputtering process. At coating process of papers constant sputtering power was applied. Phase analysis was conducted with X-ray diffraction (XRD) technique and Raman spectroscopy. Field emission scanning electron microscopy (FESEM). Cyclic voltammetry (CV) tests were carried out to reveal reversible reactions between silicon and lithium. Galvanostatic charge/discharge technique was employed to determine the cyclic performance of anodes. Electrochemical impedance spectroscopy technique was used to understand the relation between cyclic performance and internal resistance of cells. Results showed that improvement on cyclic performance of silicon anodes was achieved with novel composite silicon/graphene/MWCNT composite anode structures. (C) 2016 Elsevier B.V. All rights reserved