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Abstrak :
Vanadium-doped LiFePO4/C used as a cathode for a lithium ion battery has been successfully synthesized. In this work, LiFePO4 was synthesized from LiOH, NH4H2PO4, and FeSO4.7H2O at a stoichiometric amount. Vanadium was added in the form of H4NO3V at concentration variations and 3 wt.% carbon black. The characterization includes thermal analysis, X-ray diffraction, electron microscopy, and electrical impedance spectroscopy. The thermal analysis results showed that the LiFePO4 formation temperature is 653.8?700.0°C. The X-ray diffraction results showed an olivine structure with an orthorhombic space group, whereas the electron microscopy results showed that LiFePO4/C has a round shape with an agglomerated microstructure. Electrical impedance test results showed values of 158 Ω and 59 Ω for the as-synthesized LiFePO4/C and the 5 wt.% vanadium-doped LiFePO4/C, respectively. Cyclic performance test results at 1 C showed capacities of 24.0 mAh/g and 31.2 mAh/g for the as-synthesized LiFePO4/C and the 5 wt.% vanadium-doped LiFePO4/C, respectively. Charge and discharge test results showed charge and discharge capacities of 27.6 mAh/g and 40.2 mAh/g for the as-synthesized LiFePO4/Candthe5 wt.% vanadium-doped LiFePO4, respectively. This result is promising in terms of increasing the performance of a lithium ion battery.

Abstrak :
Vanadium-doped LiFePO4/C used as a cathode for a lithium ion battery has been successfully synthesized. In this work, LiFePO4 was synthesized from LiOH, NH4H2PO4, and FeSO4.7H2O at a stoichiometric amount. Vanadium was added in the form of H4NO3V at concentration variations and 3 wt.% carbon black. The characterization includes thermal analysis, X-ray diffraction, electron microscopy, and electrical impedance spectroscopy. The thermal analysis results showed that the LiFePO4 formation temperature is 653.8–700.0°C. The X-ray diffraction results showed an olivine structure with an orthorhombic space group, whereas the electron microscopy results showed that LiFePO4/C has a round shape with an agglomerated microstructure. Electrical impedance test results showed values of 158 ? and 59 ? for the as-synthesized LiFePO4/C and the 5 wt.% vanadium-doped LiFePO4/C, respectively. Cyclic performance test results at 1 C showed capacities of 24.0 mAh/g and 31.2 mAh/g for the as-synthesized LiFePO4/C and the 5 wt.% vanadium-doped LiFePO4/C, respectively. Charge and discharge test results showed charge and discharge capacities of 27.6 mAh/g and 40.2 mAh/g for the as-synthesized LiFePO4/C and the 5 wt.% vanadium-doped LiFePO4, respectively. This result is promising in terms of increasing the performance of a lithium ion battery.

Abstrak :
Telah dilakukan sintesis LiFePO4 melalui metode hidrotermal dengan penambahan variasi vanadium dan pelapisan karbon aktif dari bambu untuk katoda baterai litium ion. Pada sintesis LiFePO4, bahan dasar yang digunakan adalah serbuk LiOH, NH4H2PO4 dan FeSO4.7H2O yang diukur sesuai stokiometri dengan perbandingan molar 2:1:1. Setelah proses sintesis, dilakukan penambahan variasi vanadium yang berbahan dasar H4NO3V dan pelapisan karbon aktif yang berasal dari bambu sebanyak 4 wt. Pencampuran dilakukan menggunakan ball-mill lalu dikarakterisasi menggunakan analisis termal STA untuk menentukan temperatur sintering. Hasil STA menunjukkan bahwa transisi fasa mulai terjadi pada temperatur 639°C yang kemudian menjadi acuan untuk menentukan proses sintering. Hasil sintering selanjutnya dikarakterisasi menggunakan difraksi sinar-X XRD, mikroskop elektron SEM, dan spektroskopi impedansi EIS. Hasil karakterisasi dengan XRD menunjukkan bahwa fasa LiFePO4 yang terbentuk memiliki struktur berbasis olivin dengan grup ruang ortorombik serta terjadi pergeseran puncak akibat penambahan vanadium. Hasil SEM menunjukan morfologi LiFePO4 yang teraglomerasi, meskipun berkurang seiring meningkatnya kadar vanadium. Hasil uji EIS menunjukan bahwa terjadi peningkatan konduktivitas dari 2.02x10-5 S/cm pada 0 menjadi 4.37x10-5 S/cm pada 5 vanadium. Hal yang sama juga terjadi dengan adanya karbon sintesis dari gula namun pelapisan karbon aktif dari bambu menghasilkan konduktivitas yang lebih baik. ......LiFePO4 synthesis process has been carried out by hydrothermal method followed by vanadium doping and bamboo activated carbon coating for lithium ion battery cathode. In the LiFePO4 synthesis process, precursor of LiOH, NH4H2PO4 and FeSO4.7H2O was measured according to stoichiometry with 2 1 1 molar ratio. The synthesis process is produced powder LiFePO4 pure light gray.The as synthesized LiFePO4 was then mixed with H4NO3V powder and activated carbon from bamboo as much as 4 wt. Then characterized by thermal analysis STA to determine sintering temperature. The STA results show that the transition temperature starts to occur at 639°C which is then used as sintering process. The sintering results were further characterized using X ray diffraction XRD , electron microscopy SEM , and impedance spectroscopy EIS. The results of characterization by XRD show that the LiFePO4 phase formed has an olivine based structure with orthorhombic groups and a peak shift due to the addition of vanadium. The SEM results show the agglomerated lithium morphology of LiFePO4, although it decreases with increasing levels of vanadium. The result of EIS test showed that there was an increase of conductivity from 2.02x10 5 S cm at 0 to 4.37x10 5 S cm in 5 vanadium. The same is true of the carbon synthesis of sugars but the activated carbon from bamboo as a coating produces better conductivity.

Abstrak :
Faced with ever-shrinking reserves of fossil-based energy, in addition to the damaging impacts of the use of fossil-based energy sources, such as the greenhouse effect and global warming, efforts are needed to find energy alternatives. Currently under development as an alternative source of renewable energy, utilizing solar energy as its source, is a device incorporating the dye-sensitized solar cell (DSSC), which works using the simple photosynthetic-electrochemical principle at the molecular level. In this type of device, inorganic oxide semiconductors such as titanium dioxide (TiO2) offer great potential for the absorption of photon energy from the solar energy source, especially in the form of a TiO2 nanoparticle structure. In this study, a commercial TiO2 nanoparticle was used. The as-received TiO2 nanoparticle was characterized using X-ray diffraction (XRD) and a scanning electron microscope (SEM). For sensitizer, a natural dye extracted from mangosteen (Garcinia mangostana L.) pericarps was used. The extracted natural dye was characterized using Fourier transform infrared (FTIR) for the functional groups, whereas ultraviolet-visible (UV-Vis) was used to examine the absorption activity of the extracted natural dye. Performance of the DSSC was analyzed through a precision current versus potential difference (I-V) curve analyzer. The maximum power conversion efficiency (PCE) of the mangosteen natural dye was obtained using ethanol containing 20% distilled water as compared to commercial organic dye with a PCE of 4.02%. This result is convincing and promising for the next development.