Achieving fast lithium/sodium storage reaction kinetics through semiconductor hetero-interface construction derived from metal-organic framework.

The construction of heterojunction structures is an effective way to improve the lithium/sodium ion transfer rate by generating a built-in electric field. Importantly, the selection and ratio of different components affect the properties and performance of heterojunctions. Metal-organic frameworks (MOFs) as self-sacrificial template-derived materials exhibit unique properties that can improve the electrochemical performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this paper, MOF-derived heterostructures with different ratios of FeP/FeO micro- and nanostructure are designed to improve the lithium/sodium storage performance of iron-based anodes. As a representative of high FeP content, FeP/FeO-73 shows excellent capacity retention in the rate performance and long cycling performance test, in which the capacity retention of the FeP/FeO-73 anode exhibits the highest capacity retention in all of them (based on the 5th cycle capacity as reference). FeP/FeO-73 displayed capacity of 1318.5 mA h g after 100 cycles at 0.1 A g and 1393.3 mA h g after 350 cycles at 0.5 A g as LIB anode, 429 mA h g after 100 cycles at 0.1 A g for SIB. In conclusion, the calcination temperature can regulate the relative contents of FeP and FeO in the heterojunction, and the appropriate ratio of heterojunction can synergize to obtain the best electronic effect, including the optimized electronic structure and reduced diffusion energy barrier for alkali metal ions verified by density functional theory (DFT). This work provides new insights for the development and study of novel iron-based heterojunction systems.