Sintesis Natrium Alginat Termodifikasi Dopamin sebagai Binder untuk Anoda Nanosilikon dalam Baterai Ion Litium

Abstract

The potential of silicon as the anode material of future high-capacity lithium-ion batteries is still difficult to realize due to the low mobility of electrons and the material's vulnerability to damage from considerable volume expansion. The development of binders is one way to overcome this problem because a good binder can reduce the rate of electrode damage. In this research, dopamine-modified sodium alginate binders have been synthesized by sticking dopamine molecules to the sodium alginate polymer backbone through amide bonds. The modified material, NA-DA, was confirmed by Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) Spectroscopy, and UV-Vis Spectroscopy. The modified NA has new absorption at wavenumbers 1705 cm-1, 1311 cm-1, and 1026 cm-1 which are signals from the ‒CONH‒, C‒O catechol, and C‒N functional groups. The H-NMR spectrum of NA-DA shows a peak in chemical shifts of 6.7-6.9 ppm indicating the detection of aromatic protons from dopamine molecules. The signal at a wavelength of 276 cm from the UV-Vis spectrum also proved successful grafting of dopamine molecules to the sodium alginate polymer. Electrochemical tests that have been carried out on anodes using NA-DA binders show that a good anode material mass ratio for fabricating silicon electrodes with NA-DA binders is Si:AB:NA-DA = 50:30:20. It is proven that dopamine modification of sodium alginate binders results in batteries with better performance than sodium alginate without modification. However, the value of charge transfer resistance of the resulting electrode is still fairly large because the dopamine molecules attached to the backbone of sodium alginate polymer are in small quantity. This can be seen by the low intensity of aromatic proton signals in the H-NMR spectrum. CV data showed oxidation peak at 1,39 volt and reduction peak at 0,55 volt which indicates the reversibility of redox reaction inside the battery.