Structural and electrochemical performance of mo-doped Li(Ni0.8-xCo0.15Al0.05)O2 cathodes for li-ion batteries

2019-09-11
Pişkin, Berke
Savas Uygur, Cansu
Aydınol, Mehmet Kadri
Ni-based cathodes used in Li-ion batteries are suffer from structural instability during charging/discharging. It was reported in many researches that Co and Al doping to LiNiO2 (LNO) reduces the structural instability which provides better electrochemical performance as compared to bare LNO[1]. Although Li(Ni0.8Co0.15Al0.05)O2 (NCA) has been a commercialized cathode active material, further improvements in structural stabililty and electrochemical performance can be gained by either coating or doping[2-4]. In this study, bare and Mo-doped Li(Ni0.8-xCo0.15Al0.05)O2 (where x=0.2, 0.4) powders were synthesized by sol-gel technique. It was expected that Mo-doping-by reducing the nickel content- would increase the structural stability whereas increase the capacity retention since structural instability is caused by presence of nickel. Synthesis was carried out by using nitrates of each constituent element . Citric acid was used as a chelating agent and pH value was set to 4 using NH4OH (28 % NH3). After pre-calcination at 400 °C for 5 hours, calcination was carried out at 800 °C for 24 hours for formation of layered structure. Crystal structure analysis was carried out by X-ray diffraction (XRD) (Bruker D8 Advance, CuKα radiation, 2θ range of 15- 80°, 0.05 step size, 0.5°/min data collection time) and structural parameters were obtained by Rietveld refinement (MAUD Software[5]). XRD spectrums of synthesized powders were given in figure 1. Mo-doping did not cause the secondary phase formation such that all samples have single phase layered rhombohedral structure. Electrochemical properties such as capacity, rate capability and capacity retention of the synthesized powders were obtaiend by galvanostatic charge/discharge tests. Figure 2 represents the galvanostatic discharge capacity plots as preliminary results for bare and Mo-doped NCA samples. As can be seen from figure 2 that bare NCA sample has the highest first discharge capacity. In other words, Mo-doping on NCA sample does not have any contribution to the first discharge capacity. Having less nickel amount reduced the capacity of the doped samples as expected since the nickel is the prominent element which determines the capacity. For future studies cyclic voltammetry (CV) and electrochemical impedence spectroscopy will be carried out in order to better understand the effect of Mo-doping on electrochemical properties of NCA cathode material.
Citation Formats
B. Pişkin, C. Savas Uygur, and M. K. Aydınol, “Structural and electrochemical performance of mo-doped Li(Ni0.8-xCo0.15Al0.05)O2 cathodes for li-ion batteries,” presented at the mESC-IS 2019 : The Fourth International Symposium on Materials for Energy Storage and Conversion, Muğla, Turkey, 2019, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/86970.