Intercalant-induced V t _{2 g} orbital occupation in vanadium oxide cathode toward fast-charging aqueous zinc-ion batteries

Abstract

Intercalation-type layered oxides have been widely explored as cathode materials for aqueous zinc-ion batteries (ZIBs). Although high-rate capability has been achieved based on the pillar effect of various intercalants for widening interlayer space, an in-depth understanding of atomic orbital variations induced by intercalants is still unknown. Herein, we design an NH 4 + -intercalated vanadium oxide (NH 4 + -V 2 O 5 ) for high-rate ZIBs, together with deeply investigating the role of the intercalant in terms of atomic orbital. Besides extended layer spacing, our X-ray spectroscopies reveal that the insertion of NH 4 + could promote electron transition to 3 d xy state of V t 2 g orbital in V 2 O 5 , which significantly accelerates the electron transfer and Zn-ion migration, further verified by DFT calculations. As results, the NH 4 + -V 2 O 5 electrode delivers a high capacity of 430.0 mA h g −1 at 0.1 A g −1 , especially excellent rate capability (101.0 mA h g −1 at 200 C), enabling fast charging within 18 s. Moreover, the reversible V t 2 g orbital and lattice space variation during cycling are found via ex-situ soft X-ray absorption spectrum and in-situ synchrotron radiation X-ray diffraction, respectively. This work provides an insight at orbital level in advanced cathode materials.

High Flux and Stability of Cationic Intercalation in Transition-Metal Oxides: Unleashing the Potential of Mn t2g Orbital via Enhanced π-Donation

“…The ex situ sXAS results distinctly outline the reversible changes observed in the Mn L 3 edge after 200 cycles for the Ni−MnO 2 , ostensibly correlated with the cyclic Na + insertion/extraction process. 51 However, it is noteworthy that for MnO 2 , the peak intensity of the complete charge−discharge stage undergoes irreversible changes after 200 cycles. This is a clear indication of significant structural degradation of MnO 2 , accompanied by a marked increase in resistance during the process of Na + insertion/extraction.…”

Mn Cluster-Embedded N/F Co-Doped Carbon toward Mild Aqueous Supercapacitors

“…To further analyze the charge storage mechanism of different samples, we collected CV curves of NC and NCM-0.5 at various scanning rates and calculated the contribution ratio of pseudocapacitive-controlled and diffusion-controlled process based on Dunn’s method [ 31 ]: where k 1 v and k 2 v 1/2 represent the pseudocapacitive-controlled and diffusion-controlled processes, respectively. According to the calculation results, NCM-0.5 delivered a higher capacitance contribution of 68.1%.…”

2D Layered MnO2 with an Ultralarge Interlayer Spacing for Aqueous Zinc Ion Batteries

“…To overcome these problems, researchers have proposed various strategies, including nanostructure design, , composites with conductive polymers, preintercalation, − and defect engineering, to improve the electrochemical performance of δ-MnO 2 cathodes. In particular, the preintercalation strategy has proven to be a fundamental and highly effective approach for enhancing the capacity, cycle stability, and rate capability of a δ-MnO 2 cathode. , Preintercalated ions or molecules play a crucial role in increasing the interlayer spacing, facilitating ion transfer, and serving as “structural pillars” to prevent structural collapse. − Meanwhile, preintercalation can efficiently fine-tune the electronic structure of the host materials, leading to significant acceleration of electron-transfer processes. − Various ions and molecules have been previously investigated, including alkali ions, ,− NH 4 + , tetramethylammonium, Cu 2+ , Zn 2+ , Ba 2+ , La 3+ , Sn 4+ , Mo 4+ , and polyaniline . Chao et al incorporated Ba 2+ ions as interlayer pillars into δ-MnO 2 , which expanded the interlayer spacing from 0.63 to 0.70 nm, hence improving the Zn 2+ intercalation kinetics and enhancing the structural stability of δ-MnO 2 .…”