Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
Potassium ion battery seize the attention of the scientific community due to high negative potential (-2.93V Vs SHE) of the cathode materials next to Li-ion and almost having equal abundance like the Na-ion. Very recently, interesting result based on K-ion intercalating behaviour of graphite and P2-and P3-KxCoO2 was demonstrated by Komaba et al. [1-2]. Remarkable electrochemical properties of NaxCoO2 motivated us to study the K-ion intercalation behaviour. In our work, we have investigated potassium-ion intercalation behaviour of NaxCoO2 for the first time. Hexagonal P2-type NaxCoO2 platelets were synthesized by solution-combustion synthesis (SCS) method using urea as fuel and nitrate salts as reactants. Formation of hexagonal P2-type structure with the space group of P63/mmc was confirmed from X-ray Diffraction and refined the structure using GSAS software. Atomic ratio of Na:Co was analysed using inductively coupled plasma optical emission spectroscopy (ICP-OES) which is 0.84:1.0. The systematic studies carried out by assembling a K-ion half-cell with K-metal as anode and Na0.84CoO2 as active material in 0.8 M KPF6 non-aqueous electrolyte. The K-ion intercalated structure Na0.34K0.5CoO2 was delivered a reversible capacity of 82 mAh g-1 and good rate performance with columbic efficiency of 93 %. The K-ion cell with Na0.34K0.5CoO2 was cycled up to 50 cycles at C/10 rate showed excellent cycling stability [3]. The Ex-situ XRD measurements confirmed the phase transition and K-ion intercalation/de-intercalation. P2-type NaxFeO2 was prepared by SCS method and tested as cathode material for K-ion battery. The charge storage mechanism and phase transitions in P2-type NaxCoO2 and NaxFeO2 structure will be discussed.
Acknowledgement
Author B.S. gratefully acknowledges the DST (SERB), New Delhi, India (PDF/2015/00217) for providing Fellowship.
References:
1) S. Komaba et. al., Electrochem. Commun., 2015, 60, 172
2) Y. Hironaka et. al., Chem. Commun., 2017, 53, 3693
3) K. Sada et al., Chem. Commun., Submitted