Two nm Atomic Thickness Amorphous Red Phosphorus Enables Ultrafast and Ultrastable Sodium‐Ion Storage

ABSTRACT Red phosphorus (RP) has shown great potential as anode materials for sodium‐ion batteries (SIBs), but its development is hindered by sluggish Na + storage kinetics, poor intrinsic conductivity and terrible volume changes. This work focuses on the pivotal role of atomic thickness ultrasmall amorphous RP, the ultrathin amorphous RP with an atomic‐thickness of 0.9 nm exhibits a stronger Na + binding capability and this advantage becomes particularly pronounced as the RP approaches size of around 2 nm. Moreover, the developed RP anode shows exceptional expansion tolerance due to the ultrathin structure. Subsequently, the RP are integrated with highly conductive MXene, owing to the ultrasmall amorphous features of RP, the built‐in electric field at the RP/MXene heterointerface are enhanced, which significantly promotes Na + transfer and adsorption. As a result, the resulting RP‐based composites shows superior rate performance. A high capacity of 835 mAh g −1 can be maintained at high current density of 10 A g −1 . Moreover, the composites electrode delivers a reversible capacity of 1447 mA h g −1 at current density of 5 A g −1 after 1000 cycles. This study demonstrates the construction of ultrathin amorphous materials with ultra‐small size as a powerful strategy to develop fast‐charging SIBs with stable and high capacity.