Morphological convergence in solid-state synthesis: Unveiling the critical role of TiO2 precursor size for high-performance H2TiO3 lithium ion-sieves

The solid-state synthesis of H 2 TiO 3 (HTO) lithium ion-sieves is highly sensitive to the particle size of the TiO 2 precursor, which governs both structural properties and ultimate adsorption performance. This study reveals a striking morphological convergence during the synthesis of Li 2 TiO 3 (LTO) intermediates: despite employing TiO 2 precursors spanning 15-40 nm, the resulting LTO particles consistently exhibited a narrow size range of 28-32 nm, indicating a distinctive size-regulation mechanism in the solid-state reaction. In contrast, precursors ≥60 nm led to fragmented structures with reduced crystallinity. Leveraging this finding, we identified 40 nm as a critical precursor size for crafting optimal HTO adsorbents. The 40 nm-derived HTO (40-HTO) delivered a superior equilibrium Li + adsorption capacity of 58.02 mg g -1 , a pseudo-second-order rate constant 2.3-fold higher than that of its 150 nm-derived counterpart, and exceptional cyclic stability (<0.15% Ti dissolution over 10 cycles). Importantly, in a simulated concentrated brine with a high Mg 2+ /Li + mass ratio of 20, 40-HTO maintained a high Li + uptake of 36.5 mg g -1 and exhibited exceptional selectivity, with a separation factor as high as 780. This work underscores precursor size engineering, targeting a critical size threshold, as a vital strategy for developing high-efficiency lithium ion-sieves.