Scalable Assembly of Crystalline Binary Nanocrystal Superparticles and Their Enhanced Magnetic and Electrochemical...

Self-assembled binary nanocrystal superlattices (BNSLs) represent an important class of solid-state materials with potentially designed properties. In pursuit of widening the range of applications for binary superlattice materials, it is desirable to develop scalable assembly methods that enable high-quality BNSLs with tailored compositions, structures, and morphologies. Here, we report the gram-scale assembly of crystalline binary nanocrystal superparticles with high phase purity through an emulsion-based process. The structure of the resulting BNSL colloids can be tuned in a wide range (AB₁₃, AlB₂, MgZn₂, NaCl, and CaCu₅) by varying the size and/or number ratios of the two nanocrystal components. Access to large-scale, phase-pure BNSL colloids offers vast opportunities for investigating their physiochemical properties, as exemplified by AB₁₃-type CoFe₂O₄-Fe₃O₄ binary superparticles. Our results show that CoFe₂O₄-Fe₃O₄ binary superparticles not only display enhanced magnetic coupling but also exhibit superior lithium-storage properties. The nonclosed-packed NC packing arrangements of AB₁₃-type binary superparticles are found to play a key role in facilitating lithiation/delithiation kinetics and maintaining structural integrity during repeated cycling. Our work establishes the scalable assembly of high-quality BNSL colloids, which is beneficial for accelerating the exploration of multicomponent nanocrystal superlattices toward various applications.