• With the surge of global energy issue, a compatible alternative to Li- ion battery is a dire necessity. • Sodium-ion battery technology is the most attractive option to replace Li-ion battery as Na is the 6th most earth-abundant material along with similar chemical characteristics as Li. • Solid solution layered transition metal-oxide materials with ordered structure, namely, ‘Cation-ordered Rock-Salt Superstructure’ is the most promising electrodes due to: – high reversible capacity, – less voltage plateaus, and – higher cycle stability [2]. NOVEL P2-TYPE Na 0.6 Fe 0.5-2x Mn 0.5 Ti x V x O 2 CATHODE FOR HIGH-CAPACITY AND STABLE SODIUM-ION BATTERIES Trapa Banik, Dr. Indranil Bhattacharya, Webster O. Adepoju, Muhammad E. Bima, Ebrahim Nasr Esfahani Electrical and Computer Engineering Department, Tennessee Technological University OBJECTIVES INTRODUCTION AND MOTIVATION WORKING MECHANISM • Doping of Vanadium and Titanium in NaFeMnO2 cathode by sol-gel method for getting higher energy density Na-ion battery and suppressing the undesired phase transition. • Verification of stability and cyclic performance by various morphological and structural characterizations helping to compare between materials with different doping percentage. REFERENCES 1. Ni, Qiao, et al. "Polyanion‐type electrode materials for sodium‐ion batteries." Advanced Science 4.3 (2017): 1600275.Alifui-Segbaya F. Biomedical photopolymers in 3D printing. Rapid Prototyping Journal 2019; 26: 437-44. 2. Su, Heng, Saddique Jaffer, and Haijun Yu. "Transition metal oxides for sodium-ion batteries." Energy storage materials 5 (2016): 116-131. ACKNOWLEDGEMENT The authors would like to acknowledge the support provided by the Center for Energy System Research, Tennessee Valley Authority and Dept. of Electrical and Computer Engineering of Tennessee Technological University for providing the financial support to this research . METHODOLOGY FOR MATERIALS SYNTHESIS & BATTERY FABRICATION Fig.3 Battery Manufacturing Process by Sol-Gel Method DISCUSSION OF RESULTS ▪ From all the doped samples (NFM-TV’s) while compared with the pristine NFM, it is found that NFM-TV 2% gives the desired structure as for this case, the lowest volume and the largest d- spacing. Therefore, Na+-ion conductivity and discharge current rate is higher for NFM-TV 2% than Pristine NFM and other doped NFM-TV samples. ▪ The lowest TM-O bond in NFM-TV 2% also validates the structural stability and FESEM figures justifies the surface morphology. MICROSTRUCTURAL ANALYSIS (XRD & RIETVELD ANALYSIS) MORPHOLOGICAL ANALYSIS (FESEM & EDAX) DETAILED DESCRIPTION OF THE PROCESS 100 μm Properties NFM NFM-TV 1% NFM-TV 2% NFM-TV 3% NFM-TV 5% a (Å) 2.92 2.92164 2.91819 2.92215 2.92103 c (Å) 11.29 11.2964 11.2975 11.2951 11.2909 Volume (Å  ) 83.3638 83.5048 83.3158 83.5243 83.4293 d (Å) 5.64 5.64896 5.64929 5.64756 5.64583 TM-O (Å) 1.93086 2.06948 1.993742 1.97514 1.93086 R wp 7.8 7.28 8.59 6.29 5.46 R p 5 4.89 5.71 4.12 3.96 Fig.1.a) A schematic model showing interconnection of battery storage with grid and Utility b) Contrast between Na and Li c) Battery development history since past 200 years [1]. • Na-ion battery employs the sodiation /de-sodiation process for charging /discharging. • During charging, Na+ ion is extracted from cathode and inserted into anode with the electrons transport through outer circuit. • The reverse process occurs for discharging. • During this process under normal condition. The basic crystal structure should not be destroyed • An inexpensive and simple sol-gel process employed for preparing Na 0.6 Fe 0.5-2x Mn 0.5 Ti x V x O 2 (NFM-TV)with two step sintering process without pH control. • Doping of Vanadium and Titanium substitute the Jahn-Teller prone Iron concentration to reduce multiple plateaus and capacity fading [2]. Fig.6 Comparative XRD Data Analysis of XRD Data of Samples Na 0.6 Fe 0.5-2x Mn 0.5 Ti x V x O 2 (x= 0.005-0.05) Fig.2 Working Principle of Sodium–ion Battery • Diffraction peaks of all samples are well-indexed to the P63/mmc space group. • No additional diffraction peaks in NFM-TV samples, even with increase of Ti & V doping to 5 %, indicating no extra phase generated with Ti-V doping. • Primary particles are in nano- scaled pure hexagon structure (1 ~ 4 um). • Self-assembled to form secondary particles, having granular shape with size of 40~50 um. • Some needlelike nano-structures found to be formed with more Ti- V doping (NFM-TV 5%, NFM-TV 10%). • Another significant finding is primary particles of NFM-TV materials gradually deviate from its pure hexagon shape (found in pristine NFM) when the doping is increased stepwise. Fig.4 Scanning Electron Microscope Images of All Samples FESEM Analysis EDAX Analysis From the EDX elemental mapping figures, it is seen that all the elements – Mn, Fe, Ti, V and O are evenly distributed throughout the surface of the samples, validating Ti and V are doped well into the crystal structure Fig.5 Elemental Mapping from EDAX Analysis of All Samples XRD Analysis Rietveld Refinement CONCLUSION AND FUTURE WORK Fig.7 Refined Crystal Structure for NFM-TV 2% Table 1. Refined Crystal Lattice Parameters of All Samples • In this research, a novel P2-type transition metal-oxide cathode Na 0.6 Fe 0.5-2x Mn 0.5 Ti x V x O 2 was synthesized by simple sol-gel method. • A set of physicochemical analysis, including SEM and EDAX analysis, XRD and Rietveld analysis were performed to justify the morphological competence of the pristine NFM and doped NFM-TV. • These exhaustive structural and morphological comparisons provided insights on the effects of V & Ti doping on stabilizing surface structures and promoting Na + carrier transport mechanism. • The electrochemical analysis such as cyclic voltammetry and EIS analysis will be done in future for verifying the reversible capacity and rate capability. • Rietveld Refinement is executed to obtain lattice parameters and d-spacing using PDXL software, as shown in Table 1. • Both the lattice parameters a, c, and d-spacing increase with the doping of TV, except for NFM-TV 2%. • The gradual decrease in TM-O bond length infers the structural stability with doping. • The small values of reliability factors, R wp and R p (values <10) attest the reliability of the refinement calculation.