Exfoliation of Ca₃Co₄O₉ to Two-Dimensional Single-Crystalline Misfit Calcium Cobaltates for Energy Storage Applications

Layered materials have become indispensable in the development of two-dimensional (2D) systems, offering extensive specific surface area and exceptional electrical, electrochemical, and optical properties critical for diverse applications in energy storage, catalysis, sensing, and optoelectronics. While mono- and biatomic layered materials have demonstrated remarkable characteristics in lower dimensions, the quest for complexity in materials has opened new avenues for tailoring properties to specific requirements. Within this context, misfit-layered compounds (MLCs) stand out as promising candidates. In this study, we present a successful synthesis of few-layered misfit CaCoO2-CoO2 2D nanosheets in bulk quantities from bulk calcium cobalt oxide (CCO-B or CCO). These newly synthesized 2D exfoliated misfit nanosheets demonstrate remarkable 7-fold electrochemical energy storage properties, surpassing their parent bulk CCO, as cathode materials in aqueous Zn-ion batteries. This work addresses the longstanding challenge of exfoliating bulk MLCs to nanostructured, lower dimensional MLCs, opening doors for utilization in advanced energy storage systems and beyond.