Decreasing the Ion Diffusion Pathways for the Intercalation of Multivalent Cations into One-Dimensional TiS Nanobelt Arrays.

The sparse selection of available cathode materials that allow for reversible intercalation (deintercalation) of Al species represents a major hurdle in the development of efficient Al-ion batteries. Herein, we developed cathodes based on TiS nanobelts that are capable of withstanding the high charge density of Al-ion species with minimal host lattice/ion interactions. The fabricated TiS nanobelts are highly anisotropic and are directly grown on a carbon current collector yielding a spatially controlled array. The sum of evidence presented in this work indicates that one-dimensional TiS nanobelt arrays can reversibly accommodate an unprecedented amount of Al ion species within their layered structure with no significant volume expansion as well as full retention of the nanobelt morphology. Thus, the one-dimensional morphology, nanoscale dimensions, short ion diffusion paths, high electrical conductivity, and absence of additives that hinder ion migration lead to Al-based TiS electrochemical devices exhibiting high specific capacity, less capacity fade, and resilience under higher cycling rates at both room temperature and elevated temperatures when compared to TiS platelets. We also present the effects of sulfur vacancies on the electrochemical performance of Al-based TiS nanobelt array batteries. Although Al-ion batteries are still in their infancy, we believe our TiS nanobelt array cathode insertion hosts may play an important role in addressing the poor kinetics of solid-state Al-ion diffusion to enable efficient alternatives beyond lithium energy storage devices.