Nanometer-thin ZrO₂ Coating for NiO on MWCNTs as Anode for Improved Performance of Sodium-Ion Batteries

A very simple coprecipitation approach is adopted to prepare ZrO₂-coated NiO on MWCNTs nanocomposites with NiO nanoparticles within 10-15 nm size. The XPS studies confirm the presence of Zr, Ni, C, and O elements in the sample, while the BET and BJH analyses reveal a typical surface area of 204.44 m² g^-1 with pores between 10 and 15 nm. The electrochemical performance studies of the ZrO₂-coated nanocomposite electrode show a higher charge/discharge capacity of 688.3/688.7 mAh g^-1 after 200 cycles with excellent retention capacity (96%) and cycling stability. A minor capacity fading has been observed in the rate performance of the electrodes at currents ranging from 100 to 5000 mA g^-1. It also reveals that coin cells tend to maintain their maximum Coulombic efficiency of 99.9% at a low current density, revealing a notable reversible capacity. Therefore, adding MWCNTs significantly increases electrochemical performance and prevents pulverization of active materials. While structural flexibility helps in mitigating the volumetric expansion. During the cycling process, the ZrO₂ coating helps improve structural stability and facilitate the diffusion of Na ions.