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 (AB 13 , AlB 2 , MgZn 2 , NaCl, and CaCu 5 ) 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 AB 13 -type CoFe 2 O 4 −Fe 3 O 4 binary superparticles. Our results show that CoFe 2 O 4 −Fe 3 O 4 binary superparticles not only display enhanced magnetic coupling but also exhibit superior lithium-storage properties. The nonclosed-packed NC packing arrangements of AB 13 -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.
Herein, free-standing supertubes, composed of a single layer of close-packed carbon-coated nanoparticles, are fabricated by a confined-epitaxial-assembly strategy. Benefiting from the tubular geometry, monolayer superlattice structure, and uniform and conformal carbon coating, such free-standing supertubes promise high electrochemical performance while simultaneously serving as a robust platform for reliably elucidating the structure-performance relationship of lithium-ion batteries (LIBs). As a model, Fe 3 O 4 supertubes, when used as LIB anodes, can deliver a capacity of $800 mAh g À1 after 500 cycles at 5 A g À1 , outperforming most Fe 3 O 4-based materials reported previously. More importantly, the structural evolution of Fe 3 O 4 supertubes is revealed at meso-/nano-/atomic scales simultaneously upon lithiation and delithiation, which correlates well with the battery's capacity reactivation, stabilization, and degradation behaviors during the course of 500 cycles.
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