Vacancy-induced modification of the electronic band structure of LiBO2 materials as cathode surface coatings for lithium-ion batteries

Abstract

LiBO₂ is an electronic insulator and a promising multi-functional material, notably as an effective surface coating for stabilizing high-voltage cathodes in lithium-ion batteries. Despite its potential, the underlying mechanisms of lithium-ion and electron transports in the presence of lattice vacancies remain inadequately understood. This is particularly important as such lattice vacancies may either facilitate or impede charge transport. A detailed understanding of these mechanisms is essential for the rational design and optimization of LiBO₂-based materials. In our previous work [C. Ziemke, H. M. Nguyen, S. Amaya-Roncancio, J. Gahl, Y. Xing, T. W. Heitmann and C. Wexler, Formation of Lattice Vacancies and Their Effects on Li-ion Transport in LiBO₂ Crystals: A Comparative ab initio Study, J. Mater. Chem. A, 2025, 13, 3146–3162], we used density functional theory (DFT) calculations to investigate the impact of lattice vacancies on Li-ion transport in both tetragonal (t-LBO) and monoclinic (m-LBO) polymorphs of LiBO₂, revealing that B vacancies in either polymorph enhanced lithium-ion transport. In contrast, in this study we used DFT calculations to examine the effects of lattice vacancies on the electronic properties of both t-LBO and m-LBO polymorphs, focusing on the electronic band structure. Our analysis shows that B vacancies can enhance the electronic insulation of t-LBO while improving the electronic conduction of m-LBO. This finding reveals a strongly polymorph-dependent material selection, specifically the generation of B vacancies in LiBO₂ may enable t-LBO to function as a promising solid electrolyte (i.e., both a good ionic conductor and a good electronic insulator) and enhance the performance of m-LBO as a conformal cathode coating (i.e., both a good ionic conductor and a good electronic conductor) in lithium-ion batteries. Therefore, generating B vacancies, such as by neutron irradiation, would offer a viable strategy to improve the functionality of LiBO₂ as a promising material for energy storage applications. Overall, while focusing mainly on electron transport, this study complements our earlier work on ion transport and establishes a foundational understanding for future investigations of crucial aspects of LiBO₂, such as electrochemical stability, mechanical robustness, and interfacial behavior.