Ab initio study of Li, Mg and Al insertion into rutile VO₂: fast diffusion and enhanced voltages for multivalent batteries

Abstract

Vanadium oxides are among the most promising materials that can be used as electrodes in rechargeable metal-ion batteries. In this work, we systematically investigate thermodynamic, electronic, and kinetic properties associated with the insertion of Li, Mg and Al atoms into rutile VO. Using first-principles calculations, we systematically study the structural evolution and voltage curves of LiVO, MgVO and AlVO (0 < x < 1) compounds. The calculated lithium intercalation voltage starts at 3.50 V for single-atom insertion and decreases to 2.23 V for full lithiation, to the LiVO compound, which agrees well with the experimental results. The Mg insertion features a plateau about 1.6 V up to MgVO and then another plateau-like region at around 0.5 V up to MgVO. The predicted voltage curve for Al insertion starts at 1.98 V, followed by two plateaus at 1.48 V and 1.17 V. The diffusion barrier of Li, Mg and Al in the tunnel structure of VO is 0.06, 0.33 and 0.50 eV, respectively. The demonstrated excellent Li, Mg and Al mobility, high structural stability and high specific capacity suggest promising potential of rutile VO electrodes especially for multivalent batteries.

Insertion of Mono- vs. Bi- vs. Trivalent Atoms in Prospective Active Electrode Materials for Electrochemical Batteries: An ab Initio Perspective

“…Specifically, it implies that oxygen could in fact be further reduced, which is in agreement with the recently accepted notion that oxygen redox contributes to reversible capacity in electrochemical batteries, which is also easily seen in DFT calculations even in non-defected systems [22,34].…”

“…The observed oxygen redox is particularly important for the multivalent battery application of vanadium oxides, as it allows larger capacities and positive voltages beyond the traditional The observed oxygen redox is particularly important for the multivalent battery application of vanadium oxides, as it allows larger capacities and positive voltages beyond the traditional one-electron vanadium reduction chemistry. This was confirmed in [34], where we explored effects of Li, Mg and Al concentration on insertion energetics in VO 2 (R). The available experimental voltage for the full lithiation of VO 2 to LiVO 2 (~2.0 V [124]) was reasonably well matched by our computational model.…”

“…The predicted convex hulls and voltage-composition curves for Mg and Al insertions (Figure 11) demonstrate that positive voltages can be maintained up to the concentrations of MgVO 2 and Al 0.5 VO 2 (beyond the expected Mg 0.5 VO 2 and Al 0.33 VO 2 , respectively, based on vanadium redox), resulting in specific capacities among the highest for existing Mg [144][145][146] and Al [126,147,148] one-electron vanadium reduction chemistry. This was confirmed in [34], where we explored effects of Li, Mg and Al concentration on insertion energetics in VO2(R). The available experimental voltage for the full lithiation of VO2 to LiVO2 (~2.0 V [124]) was reasonably well matched by our computational model.…”

“…Stable stoichiometries on the convex hull in a binary VO 2 The most stable vanadium dioxide modification at room temperature is a semiconductor distorted rutile-type P21/c structure transforming into a metallic pure rutile-VO 2 P42/mnm polymorph above 340 K [132], a practically relevant temperature regime for many battery applications. The rutile phase is however predicted by DFT to be the most stable phase; more importantly, it is stabilized by Li insertion which makes it more stable than the semiconductor phase [34]. Stabilization of rutile VO 2 was also reported in experimental studies on hydrogen and boron doping in VO 2 nanowires [133,134].…”

Sulfur‐ and Selenium‐Containing Compounds Potentially Exhibiting Al Ion Conductivity

“…The advantages of S‐ over O‐containing compounds have been reviewed in these articles very well: even though oxidic compounds show higher possible intercalation voltages, ionic movement may be impeded owing to the higher ionicity of oxides. Their more complex (electronic) structures, which are, for example, prone to localised states and the Jahn‐Teller effect, may lead to problematic structural changes, disorder, and conversion reactions . Mobile high‐valent ions may form stronger bonds to O, increasing migration barriers .…”