Zhengping Wu

TL;DR: In this article, the effect of three different chelating agents including citric acid (CA), oxalic acid (OA), and ethylenediamine tetraacetic acid (EDTA) on spinel NiCo 2 O 4 was investigated.

TL;DR: Ion occupation and migration pathways are investigated to explore the ion-migration mechanism of Na3V2(PO4)3 with the help of first principles calculations as discussed by the authors, which generates high performances as a cathode material in sodium-ion batteries.

TL;DR: In this paper, two kinds of Na sites, namely Na(1) site and Na(2) site exist in the crystal structure per formula unit to accommodate a total of three sodium ions.

TL;DR: It is vitally important and interesting to find that there are two kinds of possible ion occupation of Na ions in Na3V2(PO4)3 and the investigation of ion-extraction number is firstly explored by discussing ion occupations with the help of first-principles calculations.

Abstract: Layered Na2FePO4F is utilized as a cathode in hybrid-ion batteries in order to explore the ion migration and diffusion capability. It is the first time that the ion migration mechanism and capability in a hybrid-ion battery is investigated by considering the activation energies of different migration ways. It is proposed that a rapid ion exchange of Na+ ions on the Na(2) site of the crystal structure with Li+ ions can take place to produce the NaLiFePO4F phase and is firstly confirmed by first principle calculations. Li+ ion conduction in NaLiFePO4F is prone to be two-dimensional (2D) in the interlayer plane with an essentially restricted migration along the [010] direction for interlayer transport due to the much higher energy value (4.53 eV for sodium ion and 1.63 eV for lithium ion). Additionally, the 2D ways which need lower activation energies along [100] and [001] directions and the small volume variation during redox cycling are responsible for the large diffusion capability with a maximum magnitude of 10−10 cm2 s−1.