First-Principles Analysis of Li Intercalation in VO₂(B)

Abstract

Bronze-phase vanadium dioxide VO 2 (B) is notable as a promising cathode material for high-capacity Li ion batteries. While various forms of VO 2 (B) nanostructures have been experimentally investigated, a comprehensive theoretical understanding of the lithium storage mechanism is still lacking. In this research, we examine the redox mechanism, structural evolution, electronic characteristics, and the kinetics of Li ion diffusion in VO 2 (B) by first-principles calculations. The impact of the surface environment on the Li ion insertion properties is also investigated. Our study demonstrates that, although VO 2 (B) is capable of incorporating one Li per formula unit from a thermodynamic perspective, its actual capacity can be much less due to kinetic factors. Energy barrier calculations reveal a pronounced compositional dependence of Li diffusion in bulk VO 2 (B): the b axis tunnels, which account for the excellent Li diffusivity at low Li content, become blocked when Li concentration goes up. The equilibrium surfaces are predicted to be oxygen-rich in an oxidizing atmosphere, which would lead to a steep gradient of Li concentration near the surfaces and further impede Li intercalation into the bulk. Yet, these limitations can be circumvented by facilitating the diffusion of Li in the c direction that is still feasible at high Li content and stabilizing the stoichiometric terminations of (0 0 1) and (1 1 0) facets, which can alleviate the load of excess Li near the surfaces. Our theoretical insights can provide a rationale for the different experimental values of specific capacity in the literature and inspire new strategies to optimize the electrochemical performance of VO 2 (B).

Mechanistic Insight into the Electrochemical Performance of Zn/VO2 Batteries with an Aqueous ZnSO4 Electrolyte

“…The structural evolution of VO 2 has been experimentally and computationally studied for Li, Na, Mg, and Al‐ion batteries . It is especially noteworthy that the intercalation of multivalent Mg and Al‐ions into VO 2 is typically accompanied by strong deformation of the crystal structure .…”

“…When the A sites are occupied, the protons are positioned at the center of four O atoms that bridge the V 4 O 10 bilayers (Figure C). At H 0.25 VO 2 , the vertical distance between the two V 4 O 10 bilayers increases, and as a consequence, the protons occupying the A sites no longer align themselves in the middle of the b axis tunnel . As the H concentration x increases from 0.25 to 0.5, the protons start to insert onto the B sites.…”

Microstructural characterization of short glass fiber and PAN based carbon fiber reinforced nylon 6 polymer composites

“…The mechanical properties of these fibers are normally probed by nano indentation method. Li et al [26] and Cao et al [27] have conducted extensive studies on mechanical properties of E-glass fibers and carbon fibers by using nano indentation method. According to them the change in elastic modulus of E-glass fibers does not affect the hardness and elastic modulus.…”

“…According to them the change in elastic modulus of E-glass fibers does not affect the hardness and elastic modulus. They also reported that as the E-glass fibers and PAN-CFs in fiber form cannot be measured using conventional mechanical testing technique, the nano indentation is a very powerful method for studying the mechanical properties of these short fibers [26,27]. The manufacturers specifications of mechanical and physical properties of E-glass fibers and AS4C grade PAN-CF are given in Table 1.…”

First-Principles Study of the Electrochemical Sodiation of Rutile-Type Vanadium Dioxide

“…where F denotes the Faraday constant. Stable intermediate phases formed throughout discharge are the ones on the convex hull of the formation energy vs. Na content plot [19,30]. Formation energies (E f ) adjusted to the energies of pristine and fully sodiated VO 2 were…”