Li⁺ Uptake in 2D BA₂PbI₄ Thin Films: A Multi-Technique Characterization

Organic/inorganic halide perovskites are a highly versatile class of materials with applications in several research fields, ranging from solar harvesting to lighting and energy storage. This work focuses on a specific 2D perovskite formulation, BA₂PbI₄, where BA stands for butylammonium, the organic component, and investigates its surface modification when in contact with a Li-ion containing electrolyte. In particular, we characterize the microscopic and spectroscopic evolution of thin perovskite layers at rest conditions and after electrochemical polarization. The combined use of atomic force microscopy and Raman spectroscopy highlights a significant interaction of the perovskite surface with the electrolyte, even without electrochemical polarization, with the formation of a characteristic morphology. Upon electrochemical cycling, the surface evolves further with the formation of solid by-products from the electrolyte decomposition. These findings are relevant in view of the future optimization of perovskites, such as 2D BA₂PbI₄, for their use in Li-ion batteries and the implementation of new strategies for real-time perovskite monitoring in an electrochemical environment.