Unlocking the electrochemistry abilities of nanoscaled Na_2/3Ni_1/4Mn_3/4O₂ thin films

Highlights: • Na_2/3Ni_1/4Mn_3/4O₂ thin films were prepared by pulsed laser deposition. • The thin film shows highly preferred c-axis orientation and is composed of homogeneous nano-sized grains. • Na_2/3Ni_1/4Mn_3/4O₂ thin film cathodes exhibit excellent cycling performance and rate capability. - Abstract: Different thickness of Na_2/3Ni_1/4Mn_3/4O₂ thin films were deposited on stainless steel substrates by pulsed laser deposition technique. X-ray diffraction and field-emission scanning electron microscope results reveal that the thin film with highly preferred c-axis orientation is composed of homogeneous nano-sized grains. The charge/discharge tests indicate that the 0.55 μm thick film demonstrates a high initial discharge capacity of 175.3 mAhg⁻¹ and a retention of 91% after 30 cycles at a current density of 13 mAg⁻¹. Furthermore, as the current density increases from 13 to 130 mAg⁻¹, about 89% of its initial discharge capacity can be maintained, exhibiting excellent rate capability. These superior electrochemical properties would promote Na_2/3Ni_1/4Mn_3/4O₂ thin film to be a promising cathode material for sodium-ion micro-batteries.