Comparative Study on the Morphology-Dependent Performance of Various CuO Nanostructures as Anode Materials for Sodium-Ion Batteries

Abstract

In this work, CuO samples with three different nanostructures, i.e., nanoflakes, nanoellipsoids, and nanorods, are successfully synthesized by a facile and environmentally friendly hydrothermal approach based on the use of different structure directing agents. The morphological influence on the anodic electrochemical performances, such as capacity, cycling stability, rate capability, and diffusion coefficient measurements of these different CuO nanostructures is comparatively investigated for sodium-ion batteries. The capacity and cycling stability are higher for the CuO nanorods (CuO-NRs) based electrode as compared to the cases of CuO nanoellipsoids (CuO-NEs) and CuO nanoflakes (CuO-NFs). At a low current density of 25 mA g −1 , the CuO-NRs based electrode exhibits an excellent reversible capacity of 600 mA h g −1 . It also exhibits a capacity of 206 mA h g −1 after 150 cycles with a capacity retention of 73% even at a higher current density of 1000 mA g −1 . The exceptional performance of CuO-NRs is attributable to its slim nanorod morphology with a smaller particle size that provides a short diffusion path and the maximized surface area facilitating good diffusion in electrolytes, ensuring good electronic conductivity and cycling stability. The comparative analysis of these materials can provide valuable insights to design hierarchical nanostructures with distinct morphology to achieve better materials designed for sodium-ion batteries.

Carbonaceous Anodes Derived from Sugarcane Bagasse for Sodium‐Ion Batteries

“…The reversible capacities of the A-HC electrodes evaluated at variousc urrent densities are shown in Table S4. [42] The measured D Na + values for the A-950 and SB-950 electrodes are 1.3 10 À11 and 3.6 10 À10 cm 2 s À1 ,r espectively.T he higherd iffusion coefficient of the latter electrode can be attributedt ot hree main factors. [15,42] The R ct values, which are related to the Nyquist semicircle diameters, are 170 and 110 W,r espectively,f or the A-950 and SB-950 electrodes.…”

“…[29,32,33,35,50] Figure 8a compares the charge-discharge profiles of the A-950 and SB-950 electrodes measured at 0.03 Ag À1 .A lthough they show similar capacities of approximately 290 mAh g À1 ,t he former electrode has more of the sloped region and less of the plateau region than the latter.T his can be attributed to the larger d-spacing (as showni nF igure S4) and more defect sites but fewer ordered graphene layers for transporting Na + to micropores in A-HC compared with those in SB-HC. [15,42] The R ct values, which are related to the Nyquist semicircle diameters, are 170 and 110 W,r espectively,f or the A-950 and SB-950 electrodes. Similart ot he trend found for the SB-HC electrodes (Table S2), the pyrolysist emperature of 950 8Cr esulted in the best high-ratep erformance, as demonstrated in Figure 8b.T he rate capabilities of the A-950a nd SB-950 electrodes are compared in Figure 8c,w hich indicates that 48 %a nd 56 %o ft he capacities measured at 0.03 Ag À1 can be retained at 2Ag À1 ,r espectively.E lectrochemical impedance spectroscopy (EIS) wasu sed to further examine the electrode impedance characteristics;t he obtained data( after five conditioningc ycles) are shown in Figure 8d.T he Nyquist spectra are composed of as emicircle at high frequency and as lopingl ine at low frequency,which can be characterizedbyt he equivalent circuits hown in the figure inset, where R e , R ct ,C PE (n % 0.86), and W are the electrolyte resistance, interfacial charge transfer resistance, interfacial constant phase element, and Warburg impedance associated with Na + diffusion in the electrode, re- spectively.…”

“…This flake-type structure is believed to be favorableb ecause the short diffusion distance in the thickness direction can facilitate Na + transport in the electrode. [42] Figures 2e,f show the high-resolution transmission electron microscopy (HRTEM;J EOL 2100F) images of SB-750 and SB-950,r espectively.B oth samples lack al ongrange graphitic structure. An increasei nt he carbon layer orderingw as observed for samples pyrolyzed at higher temperature.…”

Pseudocapacitive Graphene‐Wrapped Porous VO2 Microspheres for Ultrastable and Ultrahigh‐Rate Sodium‐Ion Storage

“…[16][17][18] Therefore, considerable efforts have been devoted to designing various carbon-based composites and hollow porous structure for improving the structural stability and electronic and ionic conductivity. [24][25][26][27] Indeed, other materials like the vanadium oxides are also promising anode materials because of their low cost, high theoretical capacity and the abundant supply of vanadium resource. [24][25][26][27] Indeed, other materials like the vanadium oxides are also promising anode materials because of their low cost, high theoretical capacity and the abundant supply of vanadium resource.…”

“…[19][20][21][22][23] Amongst, most works have focused on the oxides of Fe, Co and Ni and achieved good results. [24][25][26][27] Indeed, other materials like the vanadium oxides are also promising anode materials because of their low cost, high theoretical capacity and the abundant supply of vanadium resource. [28][29][30][31][32] Especially, the monoclinic VO 2 , which has a bilayer structure with large lattice spacing and high capacity has been widely investigated.…”