Fabrikasi Nanokomposit LiFePO4/rGO Berbasis Bahan Alam Menggunakan Kombinasi Proses Sol-Gel Dan Teknik Ultrasentrifugasi Mekanik Untuk Katoda Baterai Ion Litium

Suarso, Eka (2022) Fabrikasi Nanokomposit LiFePO4/rGO Berbasis Bahan Alam Menggunakan Kombinasi Proses Sol-Gel Dan Teknik Ultrasentrifugasi Mekanik Untuk Katoda Baterai Ion Litium. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Lithium ferro phospate (LFP) dengan struktur olivin (olivine-LiFePO4) merupakan bahan katoda yang menjanjikan untuk baterai ion litium dan telah lama dipelajari secara intensif. Tempurung kelapa sebagai biomassa diketahui memiliki konsentrasi karbon yang tinggi dan berpotensi dibentuk sebagai oksida grafena tereduksi (rGO). Salah satu tantangan dalam proses pelapisan bahan katoda LFP oleh lembaran rGO adalah mensintesis campuran homogen pada tingkat molekuler. Penelitian ini bertujuan untuk mensintesis dan mengkarakterisasi bahan katoda nanokomposit LiFePO4/rGO berbasis biomassa, memperoleh hubungan erat yang terbentuk antara nanopartikel LFP dan lembaran rGO yang mempunyai efisiensi kinerja maksimum, serta mengidentifikasi dan menganalisis pengaruh penyisipan rGO terhadap peningkatan nilai konduktivitas listrik dan kinerja elektrokimia dari bahan katoda tersebut. Tahap awal, prekursor LiFePO4 disintesis dari bahan dasar komersial menggunakan rute sol-gel, sedangkan senyawa karbon (C) mirip rGO telah dipreparasi dari limbah tempurung kelapa. Berikutnya nanopartikel LiFePO4 dikalsinasi dengan variasi temperatur 600oC, 650oC, 700oC dan 750oC dalam lingkungan gas argon selama 10 jam. Terakhir, nanokomposit LiFePO4/rGO berhasil dipreparasi menggunakan pendekatan baru yang merupakan kombinasi dari rute sol-gel dan teknik ultrasentrifugasi mekanis dengan kandungan rGO masing-masing 15%wt dan 30%wt. Selanjutnya dilakukan pengukuran karakteristik mikrostruktur dan sifat elektrokimia bahan katoda nanokomposit LiFePO4/rGO untuk baterai ion Li. Hasil analisis XRD menunjukkan bahwa partikel LFP fasa tunggal dengan struktur olivin murni dan ukuran kristal sekitar 100 nm dihasilkan pada suhu kalsinasi 750oC. Hasil uji konduktivitas, nilai optimum diperoleh untuk sampel dengan rasio massa rGO 30% sebesar 7,84 x 10-5 S/cm, mengalami peningkatan signifikan apabila dibandingkan dengan nilai konduktivitas LiFePO4 murni (orde 10-8 S/cm menjadi 10-5 S/cm). Selain menunjukkan konduktivitas listrik yang lebih baik, nanokomposit LiFePO4/rGO menunjukkan kapasitas yang lebih tinggi dan kemampuan siklus yang lebih baik. Temuan spesifik menegaskan bahwa rasio persentase katoda nanokomposit LiFePO4/rGO yang disintesis (85:15) mencapai kapasitas siklus yang lebih tinggi, dibandingkan dengan 70:30 pada level 0,1 C, dengan rata-rata pemakaian spesifik 128,03 mAhg-1 dan kapasitas retensi sebesar 97,75% setelah 50 siklus, pada suhu kamar dan laju 0,1 C. Peningkatan konduktivitas listrik dan kinerja elektrokimia sampel yang disintesis diyakini karena jaringan konduksi tiga dimensi yang dibentuk oleh rGO seperti yang diamati dengan mikroskop elektron.
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Lithium iron phosphate (LFP) with an olivine structure (LiFePO4) is a promising cathode material for Li-ion batteries and has been studied intensively for a long time. An old coconut shell as a green (sustainable) biomass was known of the high concentrate carbon and potentially can be formed as rGO. One of the challenges in the process of coating LFP cathode materials by rGO sheets is to synthesize a homogeneous mixture of rGO with electrode active materials at the molecular level. The objective of this study was synthesizing and characterizing the green biomass-based LiFePO4/rGO nanocomposite cathode material, obtaining a close relationship between LFP nanoparticles and rGO sheets substances needed for maximum performance efficiency, as well as identifying and analyzing the effect of rGO insertion on increasing electrical conductivity and electrochemical performance of the cathode material. An LiFePO4/rGO nanocomposite was successfully fabricated using an unconventional approach which is the combination of the sol–gel route and mechanical ultracentrifugation technique. LiFePO4 nanoparticles were synthesized from commercial starting materials, using the sol–gel route, and the composites’carbon weight content was varied between 15 and 30%. The samples were calcined with temperature variations of 600oC, 650oC, 700oC and 750oC in an argon environment for 10 hours. Meanwhile, an rGO – like carbon (C) compound has been prepared from coconut shell waste (biomass). Subsequently, the microstructural characteristics and electrochemical properties as cathode materials for Li ion batteries were measured. Based on the results of XRD analysis, single-phase LFP particles with a pure olivine structure and a LiFePO4 crystal size of about 100 nm were produced at a calcination temperature of 750oC. Meanwhile, according to the conductivity test analysis, the optimum result of 7.84 x 10-5 S/cm was obtained for samples with a mass ratio of 70% LFP and 30% rGO, experienced a significant increase when compared to the conductivity value of pure LiFePO4 (order 10-8 S/cm to be order of 10-5 S/cm). In addition to exhibiting better electrical conductivity, LiFePO4/rGO nanocomposites showed higher capacity and better cycle performance. The specific finding confirmed that the percentage ratio of synthesized LiFePO4/rGO nanocomposite cathode (85:15) attained higher cycle capacity, compared to 70:30 on the level of 0.1 C, with specific discharging average of 128.03 mAhg-1 and a retention capacity of 97.75% after 50 cycles, at room temperature and a rate of 0.1 C. The improved electrical conductivity and electrochemical performance of the prepared samples are believed to be done due to a three-dimensional conduction network provided by rGO-like carbon sheets as observed by electron microscopy.

Keywords: LFP (LiFePO4), LiFePO4/rGO nanocomposites, mechanical ultracentrifugation method, reduced graphene oxide (rGO) and sol–gel route

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Kata kunci: LFP (LiFePO4), metode ultrasentrifugasi mekanik, nanokomposit LiFePO4/rGO, oksida grafena tereduksi (rGO) dan rute sol-gel. ========================================================================================================================Keywords: LFP (LiFePO4), LiFePO4/rGO nanocomposites, mechanical ultracentrifugation method, reduced graphene oxide (rGO) and sol–gel route
Subjects:	Q Science > QC Physics T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK2921 Lithium cells.
Divisions:	Faculty of Science and Data Analytics (SCIENTICS) > Physics > 45001-(S3) PhD Thesis
Depositing User:	Eka Suarso
Date Deposited:	16 Feb 2022 12:23
Last Modified:	16 Feb 2022 12:23
URI:	http://repository.its.ac.id/id/eprint/94482

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