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The demand for fast charging requires high-performance battery materials with improved ionic transport. Wadsley–Roth (WR) structures have garnered attention, where the combination of blocks and shear planes addresses ionic and electronic conductivity, respectively. An improved understanding of structure–property relationships could lead to higher-performance materials. Herein, we report the first single-crystal structures of Nb12MoO33and Ta12MoO33that are consistent with other (3 × 4 × ∞) WR phases. The lithiation of Ta12MoO33is reported to enable an isostructural comparison with Nb12MoO33. These two compounds have similar unit cell volumes and atomic radii, where the Ta12MoO33unit cell is 0.2 vol % smaller. Despite the similarities in structure, the lithiation capacities, voltage windows, C rate-dependent capacities, and ionic diffusivities are distinctly different. These experimental trends align well with density functional theory calculations showing (1) a lower activation energy for Li transport within Ta12MoO33consistent with its measured 1.5–4.9-fold higher diffusion coefficients (lithiation) and (2) an ∼25% greater measured lithiation stoichiometry for Nb12MoO33, which is attributed to the calculated smaller octahedral distortions (compared to Ta12MoO33). These findings reveal that smaller channels in Ta12MoO33stabilize the transition state with 5-fold coordination, which both decreases the activation energy for diffusion and limits the extent of lithiation. Such structure–property trends help in the search for next-generation battery materials.

TiNb2O7(TNO) is a promising anode material for durable, fast-charging lithium-ion batteries that combine fast lithium diffusion with minimal lithiation strain based on a Wadsley–Roth crystal structure. Battery performance depends on a convolution of defect-sensitive material properties (lithium diffusivity and electrical resistivity) in conjunction with the architecture (feature size, porosity, and charge-transfer surface). All of these attributes connect to synthetic conditions where there is an opportunity to improve performance by understanding the interplay of changes during crystallization. Nanostructured TNO was prepared via spray drying, where variable crystallization temperature simultaneously influenced crystal structure/defects while coarsening the architecture. Comprehensive X-ray analysis (WAXS, SAXS, and XRD) and microscopy (SEM) characterized the crystallization and coarsening progress. The galvanostatic lithiation capacities (700–1100 °C) were similar at 0.1C (∼300 mAh/g); however, sample TNO-800 exhibited the highest capacity at 5C (260 ± 3 mAh/g). Intermittent current interruption (ICI) analysis revealed increasing diffusivity with calcination temperature and a nonmonotonic trend in cell resistance, minimized for TNO-800. Detailed X-ray near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and Rietveld analyses identified that crystallization led to progressive point/extended defect elimination and increasing octahedral distortion. With cell resistance including both electrical resistance and charge-transfer resistance, this overall trend reflects competition of generally improving electronic properties with calcination temperature against the coarsening architecture that progressively increases the charge-transfer resistance. The optimal TNO-800 exhibited a remarkable 10C capacity of 233 ± 1 mAh/g, which compares favorably with leading TNO precedents. This study highlights the complex convolution of atomic structure and architecture changes that occur during crystallization, which may advance other known battery materials.