ANALYSIS OF THE EFFECT OF SCANDIUM DOPING IN THE NMC 811 LITHIUM ION BATTERY CATHODE ON THE ELECTROCHEMICAL PERFORMANCE CELL

• Main Author: Ambarwati, Vita
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71286
• Institution: Institut Teknologi Bandung

The use of battery-based electric vehicles is an option to reduce CO2 emissions produced in the transportation sector from fossil-fuel vehicles. Lithium-ion batteries (LIB) are today's most widely used choice as an energy source for electric vehicles. LIB performance depends on the type of cathode used. Nickel-based cathodes, especially Ni0.8Mn0.1Co0.1O2 (NMC 811) are predicted to be widely used in electric vehicles in the future. The NMC 811 cathode is chosen due to its high capacity and specific energy and relatively lower production costs. However, batteries with NMC 811 cathodes have deficiencies in termal stability and retention capacity of charge-discharge cycles when used continuously. Therefore, many modifications have been made to the NMC cathode to improve its electrochemical performance, especially its cycle retention capacity, one of which is by doping with a particular element. Based on these facts, this research was conducted to study the effect of scandium doping on the electrochemical performance of the NMC 811 cathode cell, particularly its impact on the stability of its working cycle (capacity retention). In this research, Sc doping was carried out on the NMC 811 cathode-based using the co-precipitation method. First, NMC precursors were synthesized by reacting sulfate salts (NiSO4.6H2O, CoSO4.7H2O, and MnSO4.H2O) in 2M H2C2O4.2H2O medium as a chelating agent and NH4OH as a pH regulator for 2 hours. Next, the precipitate obtained was reacted with Sc2O3 in a solid state, then calcination was carried out at 600 oC for 6 hours and then sintering at 800 oC for 12 hours with the injection of oxygen gas. The resulting precursor was then applied to cylindrical Scdoped NMC and NMC 811 battery cells as a cathode. The variables in this cathode precursor synthesis experiment were the Sc dopant dosage, namely 0; 2.5; 5; and 7.5% mol Sc of the total moles of Ni+Mn+Co+Sc in the precursor based on NMC 811. The synthesized material for NMC 811 and NMC was doped with Sc using chemicals technical grade from the market. Products of co-precipitation, calcination, and sintering processes were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscope Energy-Dispersive X-Ray Spectroscopy (SEM-EDS). The next step was to assemble the battery cells and test the electrochemical performance of the cells by using a battery system test 8 (BST-8), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). The measurement data are then iv processed to obtain the electrochemical performance of the battery cells, including cell capacity, capacity retention in percent, ionic conductivity, and lithium-ion diffusion coefficient, and comparisons are made for each cathode variation. The investigation results showed that the addition of Sc dopant did not change the hexagonal crystal structure of NMC 811 but increased the size and regularity of the crystal structure. The morphology of the NMC 811 precursor tends to be spherical, while the Sc-doped NMC tends to be polygonal. The addition of an Sc dopant increases the diameter of the particles that make up the NMC 811 cathode precursor. The results of the FTIR analysis showed the suitability of the functional groups formed at each stage, indicating the presence of O-H, C-O, and carbonate bonds (CO3 2-) which were getting weaker (sloping) after the calcination and sintering processes. The best discharge capacity of 147.564 mAh/g is exhibited by the NMC 811 sample with an efficiency of 96.016%. Meanwhile, the best capacity retention of 87.54% was obtained in the NMC-7.5% Sc sample. From the CV measurements' results, adding Sc dopant resulted in a lower redox peak difference. The lowest redox potential peak difference of 1.02 V, which indicates the reversibility of the oxidation-reduction reaction during the charge-discharge cycle, was shown by the NMC-7.5% Sc sample. Based on the EIS measurement data, the best conductivity and lithium ion diffusion values were shown by the NMC-7.5% Sc sample with values of 3.92x10-10 cm2/s and 4.61x10-07 S/cm, respectively. The research results obtained answer the research hypothesis that the Sc doping process can increase the stability of the charge-discharge cycle and the capacity retention of NMC 811 battery cells.