Energy storage is a central challenge of modern times where continuous battery degradation is a central challenge towards realizing sustainable solutions that are simultaneously cost-competitive. This project explores Wadsley-Roth (WR) niobates, a family of complex oxides with exceptional ion and electron transport, as promising alternative electrode materials that avoid many conventional degradation mechanisms. Beyond suppression of SEI and avoiding cracking from first-order phase changes during lithiation, the inclusion of rapid ion/electron transport also limits cracking from lithiation strain under high power operation.

Our approach seeks to understand how composition, disorder, and defects govern transport and durability in this class of materials. Several examples will be given where machine learning is used with an inverse design strategy to identify new equilibrium WR phases that exhibit remarkable battery performance, e.g. MoWNb₂₄O₆₆ exhibited 225 mAh/g at 5C. Other examples will be given where defect tailoring (TiNb₂O₇) or isostructural comparisons (Nb vs Ta in M₁₂MoO₃₃ and VM₉O₂₅) led to significant performance changes where atomic scale characterizations, systematic transport measurements, and computational modeling are combined to establish design principles. The diffusion trends here are beginning to be understood in terms of interstitial volume and stabilizing coulombic interactions.

There is more broadly a need to enable comprehensive comparisons of intercalation systems. We have developed a diffusion figure-of-merit that consolidates voltage-dependent diffusivity metrics into capacity-weighted descriptors. This approach is particularly valuable for materials undergoing second-order phase transitions where redox occurs over broad voltage windows. Furthermore error minimization is critical to consider here where practices vary widely in terms of reliability and accuracy. Best-practices for accurate diffusivity analysis will be noted.

Finally, long-term cycling experiments of niobates will be briefly described with extraordinary durability. In particular mesoporous T-Nb₂O₅ can retain 90% capacity after 0.25 million cycles under optimized conditions. This longevity far surpasses typical performance for lithium-ion electrodes and directly benefits both sustainability and economics.

Scott Misture

Alfred University

Appearances