Revealing mechanism responsible for structural reversibility of single-crystal VO2 nanorods upon lithiation/delithiation

Abstract

A pure phase of VO2(B) nanorods have been synthesized through an energy-efficient microwave hydrothermal reaction and used as cathode materials of lithium ion batteries, which exhibit promising specific capacity (e.g., 130 mAh g-1 even after 100 charge/discharge cycles) and rate capacity (e.g., ~130 mAh g-1 at a high current of 400 mA g-1). The excellent cyclability originates from the structural reversibility of VO2(B) upon lithiation/delithiation that is confirmed by the in situ high-energy synchrotron X-ray diffraction (HEXRD) and in situ x-ray adsorption near-edge spectroscopy (XANES) of the VO2 nanorods in operating battery cells. The real-time results reveal that discharge forces lithium ions to insert firstly into the tunnels with the largest size along b direction followed by the second largest tunnels along c direction, which is completely reversible in the charge process.

Synchrotron‐Based X‐ray Absorption Fine Structures, X‐ray Diffraction, and X‐ray Microscopy Techniques Applied in the Study of Lithium Secondary Batteries

“…Based on the collection of real‐time electrochemical cycling data, intermediate phases were found to form during cycling reaction. While monoclinic Li‐rich Li y VO 2 phase has been found to be formed during the cycling of VO 2 , some solid‐solution intermediates have been confirmed during the electrochemical reaction LiNi 0.5 Mn 1.5 O 4 . In addition to the investigation of stable intermediates during electrochemical cycling, time‐resolution SXRD (TR‐SXRD) was used to capture and track metastable phases formed during the cycling process .…”

Highly Reversible Phase Transition Endows V6O13 with Enhanced Performance as Aqueous Zinc‐Ion Battery Cathode

“…However, V 2 O 5 suffers from the dramatic capacity deterioration on account of its inferior electronic conductivity, sluggish diffusion of ions, and terrible structural reversibility . While VO 2 is made up of distorted octahedral VO 6 units based on the oxygen body‐centered structure, vanadium atoms locate at the octahedral sites, with octahedral oxygen crystalline sharing both corners and edges, displaying the tunneled structure (Figure b) . VO 2 possesses a remarkable host framework for rapid Zn 2+ (de)intercalation, demonstrating excellent rate performance as aqueous ZIB cathodes .…”

Large Intercalation Pseudocapacitance in 2D VO2 (B): Breaking through the Kinetic Barrier

“…VO 2 (B) crystallizes in the monoclinic system (C2/ m ), and its lattice contains chains of perovskite‐like cavities interconnected along the b ‐axis through square oxygen‐bounded openings; see Figure S1 in the Supporting Information. This arrangement creates a 1D Li + ‐diffusion pathway within VO 2 (B)—parallel to the 〈010〉 crystal orientation . The electrochemical Li + insertion behavior of VO 2 (B) was first investigated by Jacobsen and co‐workers, who demonstrated that 0.5 Li/V can be inserted at ambient temperature into bulk VO 2 (B), in a two‐phase region at 2.55 V versus Li/Li + .…”

“…The other step (at 2.1 V vs Li/Li + ), however, has extremely slow kinetics. As a result, Li + intercalation capacities of 150 to 200 mAh g −1 were generally demonstrated, corresponding to 0.46 to 0.62 Li/V . Despite many attempts, the expected high capacity and cycling stability have so far not been experimentally achieved at ambient conditions.…”