| Abstract
| - Given the interest of silicates as potential electrode materials for lithium batteries, it is critical to fullyunderstand the role that the inductive effect of the polyoxyanionic group, (XO4)n-, plays on theelectrochemical performance of polyoxyanionic compounds. In this work we have combined experimentsand first-principles methods to investigate to which extent the inductive effect of the X−O bond withinthe XO4n- polyanion (X = Si, Ge0.5Si0.5, Ge, Si0.5As0.5, Si0.5P0.5, As, P) modifies the redox energy of theV5+/V4+ couple in the LiyVOXO4 family of compounds. Calculations using the GGA+U method evidencea nice correlation between the X electronegativity (i.e., the magnitude of the XO4 groups' inductiveeffect) and details of the crystalline and electronic structures of Liy+1V4+OXO4/ LiyV5+OXO4 phasessuch as bond distances or band gaps. Besides the inductive effect of the polyanionic group, we foundthat the chemistry of these 2D compounds is also correlated to the Li+ site occupancy in the interlayerspace. The calculated lithium insertion voltages display an almost linear dependence on the Mulliken Xelectronegativity; this offers promising prospects in the design of novel polyoxyanionic electrode materials.The new electrode materials Li2VOGeO4 and Li2VOSi0.5Ge0.5O4 have been electrochemically tested,providing good agreement between experimental and calculated lithium insertion voltages. Activationenergies of the prepared compounds follow the band gap trend provided by the calculated data as well.Thus, experimental evidence support the computational results and the conclusions presented here.
- Calculated and experimental lithium insertion voltages of LiyV5+OXO4 (X = Si, Ge0.5Si0.5, Ge, Si0.5As0.5, As, P) polyoxyanionic compounds display a quasilinear dependence on the Mulliken X electronegativity; this offers promising prospects in the design of novel polyoxyanionic electrode materials. Calculated bond lengths and band gaps of Liy+1V4+OXO4 and LiyV5+OXO4 compounds also correlate to the X electronegativity.
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