IRG 2: Advanced High Energy Materials
Develop nanoscale advanced materials for high-pressure water electrolyzers and high-voltage Li-ion batteries in the 5 V range in collaboration with NASA GRC and JPL, complementing parallel non-overlapping efforts carried out under PR NASA EPSCoR.
Sub-Theme A: Li ion batteries
- Promising results in case of layered composition LiNi0.66Co0.17Mn0.17O2 were obtained. Discharge capacity ~200 mAh/g at 1C rate in 4.5-2.5 V range has been observed. Experiments have been repeated by keeping the same synthesis parameters as in the earlier studies. Results were confirmed. Out line of the study is as follows. First Principles calculations were carried out to find different layered cathode material than LiCoO2 and LiNi1/3Co1/3Mn1/3O2. The basic system for the computational study was LiNi(1-x-y)CoxMnyO2 (0<x<0.17, 0<y<0.17). The computed binding energy of the transition metals in Li-layered structure have been obtained by the expression, ΔEmix=(1-x-y)E(LiNiO2)+xE(LiCoO2)+yE(LiMnO2)-E(LiNi(1-x-y)CoxMnyO2). The calculations showed that, LiNi0.66Co0.17Mn0.17O2 is a promising candidate. Its binding energy is 0.0535eV, and it’s computed average voltage is 3.48V. Due to these promising results, LiNi0.66Co0.17Mn0.17O2 was synthesized by citric acid method. The material was annealed from 800oC to 900oC for 12 h to form the α-NaFeO2 layered phase. After annealing, the cathode was spread on the Aluminum foil (25mm thickness), and storage in a glove box (Argon environment). The initial discharge capacity at a current density of 180 mA g-1 for the material annealed at 850oC was 200 mAh g-1 in the voltage range of 2.5 – 4.5 V. LiNi0.75Co0.17Mn0.08O2 also showed a binding energy of 0.0831 eV and average voltage of 3.44 V. The electrochemical studies related to LiNi0.75Co0.17Mn0.08O2 are still under study.
- During this period of time we have also synthesized composite cathode materials with Layered-Layered configuration such as xLi2MnO3-(1-x)LiNi0.5Mn0.5O2 (x=0.3) using sol-gel synthesis procedure. Sol-gel synthesis has been carried out by using metal acetates as precursors and citric acid as chelating agent in order to make a chelating complex between the metal ions. Resulting gel was calcined at desired temperature to get the crystalline phase.
X-ray diffraction study on the material was carried out in the 2θ range of 15-70 degrees. Signature of the Li2MnO3 phase was clearly observed with the peaks in between the 2θ range of 20-25 degrees. However the splitting of the peak at around 44 degrees was also observed which might be due to the improper mixing of the two compositions namely Li2MnO3 and LiNi0.5Mn0.5O2. Further work is in progress to study and over come the drawbacks of the present study. Electrochemical performance of the material was also checked. A slurry of the active material with the acetylene black and PVDF in a proper wt% ratio (80:10:10) was made using NMP and coated onto the aluminum foil which act as a current collector. Electrodes of desired area were punched out of the foil and coin cells (2032) were made using metallic lithium as anode. Removal of the Li2O, out of Li2MnO3 can has been observed at ~4.5V with a long flat plateau. Removal of Li2O is known to be irreversible. However it leaves host MnO2 in the base matrix, in which lithium can be inserted back giving rise to LiMnO2. Such kind of compositions with manganese oxidation state close to +4 and Nickel oxidation state close of +2 is not easy to fabricate at the beginning. Discharge and charge capacities of the material were calculated using initial weight of the material loaded on to the foil. A discharge capacity of ~190 mAh/g has been obtained at a charging rate of 5 mA/g. Further investigations related to the material are under study. Focus will be on the synthesis of the material using co-precipitation method.
- Number and diversity of students participating in the project including annual stipend/salary and number of hours involved for each student (i.e., research, conferences, etc.)
One undergraduate and one graduate student are working on high-energy density Li ion rechargeable batteries and high energy density electrochemical systems for 18hr/week working hours.
- Number and diversity of faculty participating in the project 3
- Documentation of each student funded under NASA URC by Co-PI with name, citizenship, major, classification, activity involvement, ethnicity and racial designation, gender, and targeted disability
Co-PI: Ram Katiyar
Lorain Torres, USA, Physics, studies on layered cathode materials, Hispanic, Female
Samuel Nieves, USA, Computer Science, Server control and Data analysis
1. Effect of the different carbon source of nanocomposite LiFePO4, Arum Kumar, R. Thomas, M. Tomar, and R. S. Katiyar, 218th ECS Meeting, Las Vegas, Nevada, (USA), October 10-15, 2010
2. Graphane-LiFePO4 nanocomposite cathode for Lithium ion batteries, Arum Kumar, Chitturi Venkateswara Rao, R. Thomas, M. S. Tomar, Y. Ishikawa, and R. S. Katiyar, 35th International Conference & Exposition on Advanced Ceramics & Composites (ICACC), Daytona Beach, Florida, January 23-28, 2011
3. Dependence of LiFePO4 electrochemical properties on the types of conductivity enhancing additives, Arum Kumar, R. Thomas, M. S. Tomar, and R. S. Katiyar, 219th ECS Meeting, Montreal, QC, Canada, May 1-6, 2011
4. LiNi0.66Co0.17Mn0.17O2 as a potential layered cathode material for Li-ion batteries, J.J. Saavedra-Arias, L. Torres, A. Manivannan, Y. Ishikawa, and R.S. Katiyar, 219th ECS Meeting, Montreal, Canada, May 1-6, 2011
Sub-Theme B: Water Electrolysis
Samples containing Iridium and Ruthenium electrodeposited onto Platinum black were previously prepared and compared to Platinum black as received and to Platinum exposed to the Iridum and Ruthenium with no applied potential. Scanning Electron Microscopy (SEM) was performed and no clear or obvious differences are present. However mappings clearly show strong presence of Iridium and Ruthenium on top of the Platinum on both electrodeposited samples. While the as received Platinum black does not, and the blank with no applied potential shows a vague presence of these elements most likely due to some adsorption of the precursors. X-ray photoelectron Spectroscopy (XPS) was also performed on all samples and high resolution analysis indicates as expected that no Iridium and Ruthenium are present on the as received Platinum, but in the no applied potential sample the presence of Ruthenium was detected. This was expected as Ruthenium adsorbs spontaneously on Platinum, nonetheless in our RoDSE (Rotating Disk Electrode) method it presents no problem as it will also undergo reduction upon polarization of the particles. Both electrodeposited samples had the Iridium and Ruthenium signal of the 4f and 3p peaks respectively, and this in contrast to the blanks is clear indication, that electrochemical reduction onto the Platinum samples was performed. The binding energies of the Iridium area highly suggest a metallic state, but in the Ruthenium other than a metallic state might be present, and that has to be analyzed to make sure. Cyclic voltammograms (CV) of the Pt black, (IrRu)/Pt black (I) and (IrRu)/Pt black (II) are presented and the electrochemical response is different for those containing the Ru and Ir, specifically in the Hydrogen adsorption and desorption regions. Which suggest changes on the surface of the Platinum. For those samples containing Ru the potential range was limited to -0.2 – 0.6 V vs Ag|AgCl, to prevent oxidation of the Ruthenium to the soluble oxide. Finally, to complement the presence of the electrodeposited material, in this case Ruthenium CO Stripping was performed, and the change in currents and onset potential is evident, still we plan to normalize these results to current density j.