Hollow nanoporous red phosphorus as an advanced anode for sodium-ion batteries

As a potential alternative to lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) have received more and more attention due to the low cost of sodium and similar chemical properties of sodium and lithium. Developing high performance anode materials is one of the major challenges for SIBs. Red phosphorus (RP) is considered as one of the most promising anodes for SIBs with a high theoretical specific capacity of about 2600 mA h g^-1, tackling serious challenges, such as large volume change and low electrical conductivity during the charge-discharge process. Herein, we have demonstrated a novel hollow nanoporous red phosphorus (HNPRP) with a small amount of iodine doping as an advanced anode for SIBs via combining a typical redox reaction and boiling process. The HNPRP exhibits a high capacity of 1658.2 mA h g^-1 after 100 cycles at 0.26 A g^-1, superior rate capability (759.6 mA h g^-1 at 5.2 A g^-1) and ultralong cycle-life (857.3 mA h g^-1 after 1000 cycles at 2.6 A g^-1) as an anode for sodium-ion batteries (SIBs). The excellent electrochemical performance is due to its innovative electrode design, which ensures high sodium ion accessibility, strong structural integrity and fast electrode transport. The scalable strategy shall pave the way for the preparation of high performance electrodes for SIBs and other energy storage systems, providing new guidelines for the synthesis of hollow nanoporous structures.