Sodium nickel oxide nanoporous cathodes used for sodium-ion rechargeable batteries

The initial research on rechargeable batteries started focusing on both Lithium and Sodium but Lithium was more attracted because of its higher energy density. Later considering the cost of lithium, research has been directed to explore the possibility of using Sodium for rechargeable batteries because of its high abundance and low cost compared to Lithium.

In this study we focuses on sodium Nickel oxide as the cathode material of the sodium iron rechargeable battery and tests were carried out to find the formation of crystal structure. Synthesis of Na_xNiO₂ nonporous active material were made using solid state reactions at 700^°C and the material development was studied by XRD characterizing technique. The developed Na_xNiO₂ was used as the active cathode material in a rechargeable half cell. The characterization confirmed the crystal structure of NaNiO₂ to be monoclinic, and also its surface morphology. Electron transition status test revealed the specific energy band gap to be 5.16 eV. Charge transfer resistance of the cathode material obtained was 13,121 Ω.

The further investigations on charge discharge revealed the maximum efficient charging rate per gram as 7.5 mA for 0.12 hours and maximum rate of discharge for maximum charge retention as 25 mA rate of charge per gram of Na_xNiO₂ which was the active material of the rechargeable cell. The charge discharge cyclability was tested for Sodium Nickel Oxide with 0.2 mA constant current for both charging and discharging. A voltage of 2.34 V was observed as the open voltage (no load) at the beginning and the half cell showed more than 180 charge-discharge cycles in performance including a rest time of one minute for each cycle. This confirmed that the battery is able to hold a fairly high reversibility.

DOI: http://dx.doi.org/10.4038/sljp.v15i0.8021

Sri Lankan Journal of Physics, Vol. 15 (2014) 19-29