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Layered P2-NaxCoO2 and P2-NaxFeO2 As Cathode Materials for Potassium-Ion Batteries

Wednesday, 4 October 2017
Prince George's Exhibit Hall D/E (Gaylord National Resort and Convention Center)
S. Baskar, K. Sada, and P. Barpanda (Indian Institute of Science, Bangalore, 560012, India)
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