Composite nanoarchitectonics for efficient lithium storage by encapsulating black phosphorus quantum dots in cobalt/iron based Prussian blue analogues

It is the critical to efficiently using black phosphorus quantum dots (BQ) in lithium batteries to obtain high energy density with improved stability. In this work, BQ was encapsulated in the size-matched pores of metalorganic frameworks (MOF) Cobalt/Iron-based Prussian blue analogues (Co/Fe-based PBA) by a coprecipitation method to construct a series of Co/Fe-based PBA@xBQ composite materials. The composite materials added with BQ exhibit significantly improved stability, demonstrating excellent electrochemical performances in lithium batteries. The close contact of BQ with Co/Fe catalytic sites promoted the rapid transfer of lithium ions between the metal sites. The unique structure of black phosphorus allowed storing more lithium ions in the pores of Co/ Fe-based PBA. Grafting the surface of MOF with BQ could reduce side reactions on the electrode surface, and their synergistic effects enhanced the lithium storage capacity. The energy density of Li||Co-Co PBA@ 8BQ and Li||Fe-Co PBA@ 10BQ batteries was 130.5 mAh & sdot;g- 1 and 187.4 mAh & sdot;g- 1 higher than the Li||Co/Fe-based PBA. Li||Fe-Co PBA@ 10BQ battery had a long cycle stability, with 70% capacity retention rate after 500 cycles. The new composite materials achieved the combination of BQ and PBA to obtain lithium batteries with higher capacity density and stability with more cycles.