OPTIMIZATION OF CALCINATION LI1.2NI0.13CO0.13MN0.54O2 (LI-RICH NCM) CATHODE SYNTHESIS USING SOLID-STATE METHOD

• Main Author: Karunawan, Jotti
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/49009
• Institution: Institut Teknologi Bandung

Li1.2Ni0.13Co0.13Mn0.54O2 (Li-rich NCM) is one of the most promising cathodes for electric vehicle applications because of high energy density. A Combination of two-layered phases Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 50% : 50 % at Li-rich NCM can perform capacity >200 mAh/g at voltage window 2 - 4.8 V. But Li-rich NCM still has low initial coulombic efficiency, capacity and voltage fading, and poor rate capabilities. Crystal structure, particle size, and surface morphology become the focus when synthesis the cathode. For electric vehicles application, solid-state synthesis is the most potent method to produce commercial-scale cathode because of an easy controlling parameter. Calcination as crystal formation is the vital step in the solid-state method. This research is focused on the optimization of the calcination process Li-rich NCM synthesis using a solid-state method. Solid-state synthesis is using acetate precursor as raw material, and calcination temperature variates from 800 oC to 950 oC. X-ray diffraction (XRD) characterization shows the clear splitting of (006)/(102) and (008)/(110) doublets and weak peaks around 20-25o that indicate complex structure multiphase layered-layered. The new peaks that indicate the spinel phase appears at high-temperature calcination 950 oC with the result that forms the layered-layered-spinel structure. Rietveld refinement analysis using GSAS II and MATCH applications shows new peaks at sample 950 oC are spinel phase Fd3m Li0.64Mn2O4 that’s amount 10.4% of all structures. Cation mixing or Ni2+ at Li+ sites is low for all of the samples. Sample 850 oC has most stoichiometric phases Li2MnO3 : LiNi1/3Co1/3Mn1/3O2 (49.4% : 50.6%). Sample 850 oC also has the best R factor and lattice ratio c/a to facilitate high Li+ ions diffusion. Scanning electron microscope (SEM) characterization shows smooth particle morphology, and size primary particle distribution is between 100 nm-580 nm. Sample 800 oC and 850 oC have a uniform size of the primary particle, but sample 900 oC and 950 oC show large aggregates that make primary particle not uniform. Confirming as the result of XRD analysis, Electrochemical impedance spectroscopy (EIS) analysis also shows that sample 850 oC has the lowest charge transfer impedance Rct (249.1 ?) and the highest ion Li+ diffusion (2.10 x 10-11 cm2/s). At the first cycle, Li-rich NCM /Li coin cell was tested with galvanostatically charging-discharging at 0.1 C within a range from 2 V to 4.8 V. Activated Li2MnO3 at high voltage can produce high capacity of samples 800 oC, 850 oC, 900 oC and 950 oC until 224.39 mAh/g, 233.92 mAh/g, 233.16 mAh/g and 224.09 mAh/g. These results are good and confirming that the sample, which has an excellent crystal structure, low charge transfer impedance, and high Li+ion diffusion produce high capacity. Galvanostatically charging-discharging for the next cycle is set to 0.2 C from 2 V to 4.6 V to reduce the electrolyte decomposition. Capacity retention 50 cycles of Li-rich NCM samples 800 oC, 850 oC, 900 oC and 950 oC are 78.66 %, 84.30 %, 82.28%, and 89.04%. The result shows that layered-layered-spinel is more stable than layered-layered structure.