CeO2-modified P2-Na-Co-Mn-O cathode with enhanced sodium storage characteristics

• Published in: RSC advances 2018-01, Vol.8 (43), p.24143-24153
• Main Authors: Wang, Yanzhi, Tang, Jiantao
• Format: Article
• Language: English
• Subjects: Cathodes; Cerium oxides; Chemistry; Crystal lattices; Cycles; Dynamic stability; Electrical resistivity; Manganese; Oxidation; Raman spectra; Rechargeable batteries; Sodium-ion batteries; Valence; X ray spectra; X-ray diffraction
• ISSN: 2046-2069
• DOI: 10.1039/c8ra04210a

To improve the cycling stability and dynamic properties of layered oxide cathodes for sodium-ion batteries, surface modified P2-Na 0.67 Co 0.25 Mn 0.75 O 2 with different levels of CeO 2 was successfully synthesized by the solid-state method. X-ray photoelectron spectra, X-ray diffraction and Raman spectra show that the P2-structure and the oxidation state of cobalt and manganese of the pristine oxide are not affected by CeO 2 surface modification, and a small amount of Ce 4+ ions have been reduced to Ce 3+ ions, and a few Ce ions have entered the crystal lattice of the P2-oxide surface during modification with CeO 2 . In a voltage range of 2.0-4.0 V at a current density of 20 mA g −1 , 2.00 wt% CeO 2 -modified Na 0.67 Co 0.25 Mn 0.75 O 2 delivers a maximum discharge capacity of 135.93 mA h g −1 , and the capacity retentions are 91.96% and 83.38% after 50 and 100 cycles, respectively. However, the pristine oxide presents a low discharge capacity of 116.14 mA h g −1 , and very low retentions of 39.83% and 25.96% after 50 and 100 cycles, respectively. It is suggested that the CeO 2 modification enhances not only the maximum discharge capacity, but also the electric conductivity and the sodium ion diffusivity, resulting in a significant enhancement of the cycling stability and the kinetic characteristics of the P2-type oxide cathode. The CeO 2 modification significantly enhances the maximum discharge capacity and cycling stability of a P2-Na 0.67 Co 0.25 Mn 0.75 O 2 cathode.