High performance NaxCoO2 as a cathode material for rechargeable sodium batteries

Abstract

Sodium cobalt oxide (NCO) has been synthesized by a glycine assisted sol–gel combustion method. XRD studies confirm the P2 phase formation of NCO. Na exists in two different environments in the NCO crystallite structure, which is confirmed by ²³Na Nuclear Magnetic Resonance spectra (NMR). Morphological studies confirm that the particles are unique with a stacked hexagonal shape. Galvanostatic charge/discharge studies performed at different current rates (0.1, 0.2 and 0.5) deliver reversible specific capacities of 126, 108 and 77 mA h g⁻¹ respectively. Further, cycle life performance of the fabricated cells after 50 cycles at 0.1 C rate exhibits an average discharge capacity of ~121 mA h g⁻¹ with a capacity retention of ~86% (Coulombic efficiency ~99.9%). The investigated NCO's superior performance suggests its suitability as a cathode material for Na-ion batteries.