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Evaluating electrochemical properties of layered Na x Mn 0.5 Co 0.5 O 2 obtained at different calcined temperatures
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  • Hoang Nguyen,
  • Minh Le Nguyen,
  • Doan My Ngoc Nguyen,
  • Minh Kha Le,
  • Van Man Tran,
  • My Loan Phung LE
Hoang Nguyen
University of Science

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Minh Le Nguyen
University of Science
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Doan My Ngoc Nguyen
University of Science
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Minh Kha Le
Vietnam National University Ho Chi Minh City
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Van Man Tran
University of Science
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My Loan Phung LE
University of Science
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Abstract

This work elucidated the structure and electrochemical performance of the layered cathode material Na xMn 0.5Co 0.5O 2 (NMC) with x~1 calcined at 650, 800 and 900 oC. XRD diffraction indicated that the NMC material possessed a phase transition from P3- to P2-type layered structure with bi-phasic P3/P2 at medium temperature. The sodium storage performance was evaluated by constant current charging/discharging. Specifically, P2-NMC exhibits the highest initial capacity of 156.9 mAh.g -1 with capacity retention of 76.2% after 100 cycles, which is superior to the initial discharge capacity is only 149.3 mAh.g -1 and severe capacity fading per cycle of P3-NMC, indicating high robust structure stability by calcined at the higher temperature. Additionally, the best performance of P2-NMC also demonstrated by the high-rate capability that delivered a capacity of 50 mAh.g -1 at charge/discharge rate up to 10C. The sodium diffusion coefficient of Na + ions into the P2-type layered structure obtained by Cyclic Voltammetry (CV) was in the range of 10 −13–10 −12 cm 2.s −1, which is inferior to the others. However, the structure stability of P2 phase contributed to the best prerformance in sodium-ion half-cell.